Dietary Treatment for Overweight and Obesity - Americans' Diets
About 11% of Americans' daily calories were derived from saturated fat—too much according to 2000 U.S. Dietary Guidelines calling for less than 10% of daily calorie intake from saturated fat. On average, males consumed more than the recommended limit of 300 mg per day of cholesterol while females consumed just 225 mg per day. In addition, the average daily salt consumption for all age groups over six years of age was well above the upper limit of 2,400 mg of sodium per day recommended by the National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.
The USDA confirms that Americans' diets contained more calories and refined carbohydrates in 2000 than they had fifteen years earlier (Judy Putnam et al., U.S. Per Capita Food Supply Trends: More Calories, Refined Carbohydrates, and Fats, December 2002). Average daily calorie consumption in the United States in 2000 was 12%, or about 300 calories, more than in 1985. Of this increase, grains (mainly refined grains) accounted for 46%, added fats 24%, added sugars 23%, fruits and vegetables 8%, and the meat and dairy groups together declined 1%. Per capita consumption of dietary fat, which was relatively unchanged from 1985 to 1999, jumped 6% in 2000. American diets were also found lacking in whole grains and other nutritious foods.
Dietary Guidelines for Americans 2005
Every five years, the Dietary Guidelines for Americans are updated and revised to translate the most current scientific knowledge about individual nutrients and food components into dietary recommendations that may be adopted by the public. The recommendations are based on the preponderance of scientific evidence for reducing the risk of chronic disease and promoting health. While the recommendations focus on nutritional content, they recognize that a combination of poor diet and physical inactivity can lead to chronic diseases that include cardiovascular disease, Type 2 diabetes, hypertension, osteoporosis, and certain cancers.
The sixth edition of the Dietary Guidelines, issued in January 2005, characterize a healthy diet as one that includes plenty of fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products, as well as lean meats, poultry, fish, beans, eggs, and nuts. A healthy diet also is low in saturated fats, trans fats—artificial fats created through the hydrogenation of oils, which solidifies the oil and limits the body's ability to regulate cholesterol—cholesterol, salt, and added sugars. Specific recommendations stipulate that fewer than 10% of calories should come from saturated fatty acids, and trans fatty acids, considered to be the most harmful to health, should be avoided. Cholesterol intake should be less than 300 mg/day. Total fat intake should not exceed 20% to 35% of calories. Preferred fat sources are fish, nuts, and vegetable oils containing polyunsaturated and monounsaturated fatty acids. Lean, low-fat, or fat-free meats, poultry, dry beans, and milk or milk products are preferable to full-fat foods.
In general, the Guidelines encourage most Americans to eat fewer calories, increase their physical activity, and to choose nutrient-dense foods. They advocate increased consumption of fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products. For example, two cups of fruit and 2½ cups of vegetables per day are recommended for a 2,000-calorie diet along with three or more servings of whole-grain products per day and three cups per day of fat-free or low-fat milk or equivalent milk products.
Two examples—the DASH (Dietary Approaches to Stop Hypertension) eating plan and USDA Food Guide—offer instruction about how to allocate calories to various food groups. Table 5.1 shows the amounts of various food groups that are recommended each day or each week in the USDA Food Guide and in the DASH Eating Plan at the 2,000-calorie level as well as equivalent amounts for different food choices in each group. Acknowledging Americans' tendencies to eat out and eat while commuting, running errands, or working, the Guidelines also offer tips for making healthy choices away from home. (See Table 5.2.)
TABLE 5.1 Sample USDA Food Guide and the DASH Eating Plan at the 2,000-calorie levela
| TABLE 5.1 | |||||
|---|---|---|---|---|---|
| Sample USDA Food Guide and the DASH Eating Plan at the 2,000-calorie levela | |||||
| Food groups and subgroups | USDA Food Guide amountb | DASH Eating Plan amount | Equivalent amounts | ||
| aAll servings are per day unless otherwise noted. USDA vegetable subgroup amounts and amounts of DASH nuts, seeds, and dry beans are per week. | |||||
| bThe 2,000-calorie USDA Food Guide is appropriate for many sedentary males 51 to 70 years of age, sedentary females 19 to 30 years of age, and for some other gender/age groups who are more physically active. | |||||
| cIn the DASH Eating Plan, nuts, seeds, and dry beans are a separate food group from meat, poultry, and fish. | |||||
| dThe oils listed in this table are not considered to be part of discretionary calories because they are a major source of the vitamin E and polyunsaturated fatty acids, including the essential fatty acids, in the food pattern. In contrast, solid fats (i.e.. saturated and trans fats) are listed separately as a source of discretionary calories. | |||||
| SOURCE: "Table 1. Sample USDA Food Guide and the DASH Eating Plan at the 2,000-Calorie Level," in Dietary Guidelines for Americans, 2005, Chapter 2: Adequate Nutrients within Calorie Needs, U.S. Department of Health and Human Services, U.S. Department of Agriculture, January 12, 2005, http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter2.htm (accessed January 12, 2006) | |||||
| Fruit group | 2 cups (4 servings) | 2 to 2.5 cups (4 to 5 servings) | 1/2 cup equivalent is: 1/2 cup fresh, frozen, or canned fruit 1 med fruit 1/4 cup dried fruit USDA: 1/2 cup fruit juice DASH: 3/4 cup fruit juice |
||
| Vegetable group Dark green vegetables Orange vegetables Legumes (dry beans) Starchy vegetables Other vegetables |
2.5 cups (5 servings) 3 cups/week 2 cups/week 3 cups/week 3 cups/week 6.5 cups/week |
2 to 2.5 cups (4 to 5 servings) | 1/2 cup equivalent is: 1/2 cup of cut-up raw or cooked vegetable 1 cup raw leafy vegetable USDA: 1/2 cup vegetable juice DASH: 3/4 cup vegetable juice |
||
| Grain group Whole grains Other grains |
6 ounce-equivalents 3 ounce-equivalents 3 ounce-equivalents |
7 to 8 ounce-equivalents (7 to 8 servings) | 1 ounce-equivalent is: 1 slice bread 1 cup dry cereal 1/2 cup cooked rice, pasta, cereal DASH: 1 oz dry cereal (1/2-1/4 cup depending on cereal type—check label) |
||
| Meat and beans group | 5.5 ounce-equivalents | 6 ounces or less meat, poultry, fish 4 to 5 servings per week nuts, seeds, and dry beansc |
1 ounce-equivalent is: 1 ounce of cooked lean meats, poultry, fish 1 egg USDA: 1/4 cup cooked dry beans or tofu, 1 Tbsp peanut butter, 1/2 oz nuts or seeds DASH: 1 1/2 oz nuts, 1/2 oz |
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| Milk group | 3 cups | 2 to 3 cups | 1 cup equivalent is: 1 cup low-fat/fat-free milk, yogurt 1 1/2 oz of low-fat or fat- free natural cheese 2 oz of low-fat or fat-free processed cheese |
||
| Oils | 27 grams (6 tsp) | 8 to 12 grams (2 to 3 tsp) | 1 tsp equivalent is: DASH: 1 tsp soft margarine 1 Tbsp low-fat mayo 2 Tbsp light salad dressing 1 tsp vegetable oil |
||
| Discretionary calorie allowance Example of distribution: Solid fatd Added sugars |
267 calories | ∼2 tsp of added sugar (5 Tbsp per week) |
1 Tbsp added sugar equivalent is: DASH: 1 Tbsp jelly or jam 1/2 oz jelly beans 8 oz lemonade |
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| 18 grams 8 tsp |
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The Guidelines specifically address weight management, advising Americans: "To maintain body weight in a healthy range, balance calories from foods and beverages with calories expanded" and "To prevent gradual weight gain over time, make small decreases in food and beverage calories and increase physical activity." For people who are overweight, the guidelines advise gradual, steady weight loss achieved by decreasing caloric consumption while maintaining sufficient nutrients and increasing physical activity. Parents of overweight children are counseled to reduce the rate of weight gain while children grow and develop and to consult a health-care provider before placing children on weight-reduction diets. Pregnant women are advised to gain weight as instructed by their health-care providers, and breastfeeding mothers are reassured that modest weight loss is safe and will not harm the development of nursing infants. Overweight adults and children with chronic diseases and those on medication are cautioned to consult with healthcare providers before embarking on a weight-loss program.
While academicians and health-care providers often view the Guidelines as a compromise between science and politics—nutrition advocates and the food and agriculture lobbies—the debut of the 2005 guidelines was greeted with less criticism than usual. Still, Dena Bravata, a physician and obesity researcher, asserted in "Food FAQs" (Nature, February 24, 2005), that the 2005 Dietary Guidelines were created using a formula that calculates the nutritional value of each food group to
TABLE 5.2
Don't give in when you eat out and are on the go
It's important to make smart food choices and watch portion sizes wherever you are—at the grocery store, at work, in your favorite restaurant, or running errands. Try these tips
- At the store, plan ahead by buying a variety of nutrient-rich foods for meals and snacks throughout the week
- When grabbing lunch, have a sandwich on whole-grain bread and choose low-fat/fat-free milk, water, or other drinks without added sugars
- In a restaurant, opt for steamed, grilled, or broiled dishes instead of those that are fried or sautÉed.
- On a long commute or shopping trip, pack some fresh fruit, cut-up vegetables, string cheese sticks, or a handful of unsalted nuts—to help you avoid impulsive, less healthful snack choices.
SOURCE: "Don't Give in When You Eat Out and Are on the Go," in in Dietary Guidelines for Americans, 2005, U.S. Department of Health and Human Services, U.S. Department of Agriculture, January 12,2005, http://www.health.gov/dietaryguidelines/dga2005/document/media/OnThetGo.pdf (accessed January 12,2006)
reflect what Americans actually eat rather than what they should eat.
HOW WEIGHT-LOSS DIETS WORK
Research demonstrates that weight loss is associated with the length of the diet, pre-diet weight (people who are more overweight tend to lose more weight, more quickly than those who are only mildly overweight), and the number of calories consumed. Any diet that restricts caloric intake such that calories consumed are less than those expended will promote short-term weight loss. The key to weight loss through diet is adherence—if people do not stick to their diets, then they will not lose weight. As early as the 1860s, William Banting, describing the benefits of his low-carbohydrate diet, wrote that "The great charms and comfort of the system are that its effects are palpable within a week of trial and creates a natural stimulus to persevere for a few weeks more."
The successes achieved using regimens that restrict dieters to a single food or food group such as grapefruits, pineapples, or cabbage are probably in part attributable to the human hankering for variety. Limited to just one food, most dieters experience boredom—there is just no appeal to eating the same food at every meal, for days on end, so naturally, less food is consumed. In addition, these diets generally rely on low-calorie foods, so that even if dieters were inspired to consume ten grapefruits per day, their total daily caloric consumption would be about 1,200 calories, which is sufficient to produce weight loss for most people who are overweight. Similarly, diets that involve stringent portion control effectively reduce calories to produce weight loss.
Low-Calorie Diets
Traditional dietary therapy for weight loss generally seeks to create a deficit of 500 to 1,000 calories per day
TABLE 5.3 Low-calorie Step I diet
| TABLE 5.3 | |
|---|---|
| Low-Calorie Step I diet | |
| Nutrient | Recommended intake |
| aA reduction in calories of 500 to 1,000 kcal/day will help achieve a weight loss of 1 to 2 pounds/week. Alcohol provides unneeded calories and displaces more nutritious foods. Alcohol consumption not only increases the number of calories in a diet but has been associated with obesity in epidemiologic studies as well as in experimental studies. The impact of alcohol calories on a person's overall caloric intake needs to be assessed and appropriately controlled. | |
| bFat-modified foods may provide a helpful strategy for lowering total fat intake but will only be effective if they are also low in calories and if there is no compensation by calories from other foods. | |
| cPatients with high blood cholesterol levels may need to use the Step II diet to achieve further reductions in LDL-cholesterol levels; in the Step II diet, saturated fats are reduced to less than 7 percent of total calories, and cholesterol levels to less than 200 mg/day. All of the other nutrients are the same as in Step I. | |
| dProtein should be derived from plant sources and lean sources of animal protein. | |
| eComplex carbohydrates from different vegetables, fruits, and whole grains are good sources of vitamins, minerals, and fiber. A diet rich in soluble fiber, including oat bran, legumes, barley, and most fruits and vegetables may be effective in reducing blood cholesterol levels. A diet high in all types of fiber may also aid in weight management by promoting satiety at lower levels of calorie and fat intake. Some authorities recommend 20 to 30 grams of fiber daily, with an upper limit of 35 grams. | |
| fDuring weight loss, attention should be given to maintaining an adequate intake of vitamins and minerals. Maintenance of the recommended calcium intake of 1,000 to 1,500 mg/day is especially important for women who may be at risk of osteoporosis. | |
| SOURCE: "Table 4. Low-Calorie Step I Diet," in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, October 2000, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12, 2006) | |
| Caloriesa | Approximately 500 to 1,000 kcal/day reduction from usual intake |
| Total fatb | 30 percent or less of total calories |
| Saturated fatty acidsc | 8 to 10 percent of total calories |
| Monounsaturated fatty acids | Up to 15 percent of total calories |
| Polyunsaturated fatty acids | Up to 10 percent of total calories |
| Cholesterolc | <300 mg/day |
| Proteind | Approximately 15 percent of total calories |
| Carbohydratee | 55 percent or more of total calories |
| Sodium chloride | No more than 100 mmol/day (approximately 2.4 g of sodium or approximately 6 g of sodium chloride) |
| Calciumf | 1,000 to 1,500 mg/day |
| Fibere | 20 to 30 g/day |
with the intent of promoting weight loss of between one to two pounds per week. Low-calorie diets (LCDs) for men usually range from 1,200 to 1,600 calories per day; for women LCDs contain between 1,000 and 1,200 calories per day. Table 5.3 is an example of the recommended percentages of nutrients in an LCD that aims to decrease risk factors for hypertension and high cholesterol as well as cause weight loss.
The most successful LCDs take individual food preferences into account to custom-tailor the diet. Table 5.4 and Table 5.5 show examples of how traditional American cuisine may be used to create a low-calorie diet containing 1,200 and 1,600 calories per day respectively. Table 5.6 incorporates regional Southern cuisine into a reduced-calorie diet. Table 5.7 illustrates how Asian-American cuisine may be adapted to 1,200- and 1,600-calorie-per-day diets, and Table 5.8 shows how Mexican-American cuisine may be adapted for low-calorie diets. Table 5.9 is a sample of a reduced-calorie
TABLE 5.4 Sample reduced calorie menus, traditional American cuisine—1,200 calories
| TABLE 5.4 | ||||||
|---|---|---|---|---|---|---|
| Sample reduced calorie menus, traditional American cuisine-1,200 calories | ||||||
| Calories | Fat (grams) | % Fat | Exchange for | |||
| Calories | 1,247 | Saturated fat, % Kcals | 7 | |||
| Total Carbohydrate, % Kcals | 58 | Cholstrol, mg | 96 | |||
| Total fat, % Kcals | 26 | Protein, % Kcals | 19 | |||
| *Sodium, mg | 1,043 | |||||
| Note: Calories have been rounded. | ||||||
| 1,200: 100% RDA met for all nutrients except vitamin E 80%, vitamin B2 96%, vitamin B6 94%, calcium 68%, iron 63%, and zinc 73%. | ||||||
| *No salt added in recipe preparation or as seasoning. Consume at least 32 ounces of water. | ||||||
| SOURCE: "Appendix D. Traditional American Cuisine—1,200 Calories," in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, October 2000, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12, 2006) | ||||||
| Breakfast | ||||||
| • Whole wheat bread, 1 medium slice | 70 | 1.2 | 15 | (1 bread/starch) | ||
| • Jelly, regular, 2 tsp | 30 | 0 | 0 | (1/2 fruit) | ||
| • Cereal, shredded wheat, 1/2 cup | 104 | 1 | 4 | (1 bread/starch) | ||
| • Milk, 1%, 1 cup | 102 | 3 | 23 | (1 milk) | ||
| • Orange juice, 3/4 cup | 78 | 0 | 0 | (1 1/2 fruit) | ||
| • Coffee, regular, 1 cup | 5 | 0 | 0 | (free) | ||
| Breakfast total | 389 | 5.2 | 10 | |||
| Lunch | ||||||
| • Roast beef sandwich | ||||||
| Whole wheat bread, 2 medium slices | 139 | 2.4 | 15 | (2 bread/starch) | ||
| Lean roast beef, unseasoned, 2 oz | 60 | 1.5 | 23 | (2 lean protein) | ||
| Lettuce, 1 leaf | 1 | 0 | 0 | (1 vegetable) | ||
| Tomato, 3 medium slices | 10 | 0 | 0 | |||
| Mayonnaise, low calorie, 1 tsp | 15 | 1.7 | 96 | (1/3 fat) | ||
| • Apple, 1 medium | 80 | 0 | 0 | (1 fruit) | ||
| • Water, 1 cup | 0 | 0 | 0 | (free) | ||
| Lunch total | 305 | 5.6 | 16 | |||
| Dinner | ||||||
| • Salmon, 2 ounces edible | 103 | 5 | 44 | (2 lean protein) | ||
| • Vegetable oil, 1 1/2 tsp | 60 | 7 | 100 | (1 1/2 fat) | ||
| • Baked potato, 3/4 medium | 100 | 0 | 0 | (1 bread/starch) | ||
| • Margarine, 1 tsp | 34 | 4 | 100 | (1 fat) | ||
| • Green beans, seasoned, with margarine, 1/2 cup | 52 | 2 | 4 | (1 vegetable) (1/2 fat) | ||
| • Carrots, seasoned | 35 | 0 | 0 | (1 vegetable) | ||
| • White dinner roll, 1 small | 70 | 2 | 28 | (1 bread/starch) | ||
| • Iced tea, unsweetened, 1 cup | 0 | 0 | 0 | (free) | ||
| • Water, 2 cups | 0 | 0 | 0 | (free) | ||
| Dinner total | 454 | 20 | 39 | |||
| Snack | ||||||
| • Popcorn, 2 1/2 cups | 69 | 0 | 0 | (1 bread/starch) | ||
| • Margarine, 3/4 tsp | 30 | 3 | 100 | (3/4 fat) | ||
| Total | 1,247 | 34-36 | 24-26 | |||
Research reveals that reducing fat in the diet is an effective way to reduce calories, and that when low-calorie diets are combined with low-fat diets, better weight loss is achieved than through calorie reduction alone. Further, while very-low-calorie diets that provide about 500 calories per day have been demonstrated to produce greater initial weight loss than the low-calorie diets, the long-term weight loss is not different between the two regimens.
Low-Carbohydrate Diets
During 2004 and 2005 several rigorous research studies reported that low-carbohydrate diets were as effective, or even more effective, in producing short-term weight loss than low-fat diets. The low-carbohydrate diets owed much of their success to adherence—dieters were better able to stick with their diets, and as a result achieved better results. Another hypothesis about the success of low-carbohydrate regimens is that dieters do not feel as hungry as they do on other diets because protein is the most satisfying of the three macronutrients—carbohydrates, fats, and protein.
The scientific premise of low-carbohydrate diets is that consuming certain carbohydrates can cause surges in blood sugar and insulin that not only stimulate appetite
TABLE 5.5 Sample reduced calorie menus, traditional American cuisine—1,600 calories
| TABLE 5.5 | ||||||
|---|---|---|---|---|---|---|
| colspan="7">Sample reduced calorie menus, traditional American cuisine—1,600 calories | ||||||
| Calories | Fat (grams) | % Fat | Exchange for | |||
| Calories | 1,613 | Saturated fat, % kcals | 8 | |||
| Total Carbohydrate, % kcals | 55 | Cholesterol, mg | 142 | |||
| Total fat, % kcals | 29 | Protein, % kcals | 19 | |||
| *Sodium, mg | 1,341 | |||||
| Note: Calories have been rounded. | ||||||
| 1,600: 100% RDA met for all nutrients except vitamin E 99%, iron 73%, and zinc 91%. | ||||||
| No salt added in recipe preparation or as seasoning. Consume at least 32 ounces of water. | ||||||
| SOURCE: "Appendix D. Traditional American Cuisine—1,600 Calories," in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, October 2000, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12, 2006) | ||||||
| Breakfast | ||||||
| • Whole wheat bread, 1 medium slice | 70 | 1.2 | 15.4 | (1 bread/starch) | ||
| • Jelly, regular, 2 tsp | 30 | 0 | 0 | (1/2 fruit) | ||
| • Cereal, shredded wheat, 1 cup | 207 | 2 | 8 | (2 bread/starch) | ||
| • Milk, 1%, 1 cup | 102 | 3 | 23 | (1 milk) | ||
| • Orange juice, 3/4 cup | 18 | 0 | 0 | (1 1/2 fruit) | ||
| • Coffee, regular, 1 cup | 5 | 0 | 0 | (free) | ||
| • Milk, 1%, 1 oz | 10 | 0.3 | 27 | (1/8milk) | ||
| Breakfast total | 502 | 6.5 | 10 | |||
| Lunch | ||||||
| • Roast beef sandwich: | ||||||
| Whole wheat bread, 2 medium slices | 139 | 2.4 | 15 | (2 bread/starch) | ||
| Lean roast beef, unseasoned, 2 oz | 60 | 1.5 | 23 | (2 lean protein) | ||
| American cheese, low fat and low sodium, 1 slice, 3/4 oz | 46 | 1.8 | 36 | (1 lean protein) | ||
| Lettuce, 1 leaf | 1 | 1 | 0 | |||
| Tomato, 3 medium slices | 10 | 0 | 0 | (1 vegetable) | ||
| Mayonnaise, low calorie, 2 tsp | 30 | 3.3 | 99 | (2/3 fat) | ||
| • Apple, 1 medium | 8 | 0 | 0 | (1 fruit) | ||
| • Water, 1 cup | 0 | 0 | 0 | (free) | ||
| Lunch total | 366 | 9 | 22 | |||
| Dinner | ||||||
| • Salmon, 3 ounces edible | 155 | 7 | 40 | (3 lean protein) | ||
| • Vegetable oil, 1 1/2 tsp | 60 | 7 | 100 | (1 1/2 fat) | ||
| • Baked potato, 3/4 medium | 100 | 0 | 0 | (1 bread/starch) | ||
| • Margarine, 1 tsp | 34 | 4 | 100 | (1 fat) | ||
| • Green beans, seasoned, with margarine, 1/2 cup | 52 | 2 | 4 | (1 vegetable) (1/2 fat) | ||
| • Carrots, seasoned, with margarine, 1/2 cup | 52 | 2 | 4 | (1 vegetable) (1/2 fat) | ||
| • White dinner roll, 1 medium | 80 | 3 | 33 | (1 bread/starch) | ||
| • Ice milk, 1/2 cup | 92 | 3 | 28 | (1 bread/starch) (1/2 fat) | ||
| • Iced tea, unsweetened, 1 cup | 0 | 0 | 0 | (free) | ||
| • Water, 2 cups | 0 | 0 | 0 | (free) | ||
| Dinner total | 625 | 28 | 38 | |||
| Snack | ||||||
| • Popcorn, 2 1/2 cups | 69 | 0 | 0 | (1 bread/starch) | ||
| • Margarine, 1/2 tsp | 58 | 6.5 | 100 | (1 1/2 fat) | ||
| Total | 1,613 | 50 | 28 | |||
Examples of single sugars from foods include fructose, which is found in fruits, and galactose, which is found in milk products. Double sugars include lactose in dairy products; maltose, which is found in certain vegetables and in beer; and sucrose (table sugar). Examples of complex carbohydrates, often referred to as "starches" are breads, cereals, legumes, brown rice, and pastas. Simple carbohydrates occur naturally in fruits, milk products, and vegetables; at the same time, these foods also contain vitamins and minerals. The simple carbohydrates most nutritionists call "empty calories" are the processed and refined sugars found in candy, table sugar, and sodas, as well as such foods as white flour, sugar, and polished rice (unless they are labeled "enriched" or "fortified" with vitamins or other nutrients).
In addition to distinguishing between simple and complex carbohydrates, low-carbohydrate regimens rely on a measure known as the glycemic index (GI), which ranks foods based on how rapidly their consumption raises blood glucose levels. The GI measures how much
TABLE 5.6 Sample reduced calorie menus, Southern cuisine
| TABLE 5.6 | |||
|---|---|---|---|
| Sample reduced calorie menus, Southern cuisine | |||
| 1,600 calories | 1,200 calories | ||
| Calories | 1,653 | Calories | 1,225 |
| Total carbohydrate, % kcals | 53 | Total carbohydrate, % kcals | 50 |
| Total fat, % kcals | 28 | Total fat, % kcals | 31 |
| *Sodium, mg | 1,231 | *Sodium, mg | 867 |
| Saturated fat, % kcals | 8 | Saturated fat, % kcals | 9 |
| Cholesterol, mg | 172 | Cholesterol, mg | 142 |
| Protein, % kcals | 20 | Protein, % kcals | 21 |
| 1,600: 100% RDA met for all nutrients except vitamin E 97%, magnesium 98%, iron 78%, and Zinc 90%. | |||
| 1.200: 100% RDA met for all nutrients except vitamin E 82%, vitamin B1 & B2 95%, vitamin B 99%, vitamin B 88%, magnesium 83%, iron 56%, and zinc 70%. | |||
| *No salt added in recipe preparation or as seasoning. Consume at least 32 ounces of water. | |||
| SOURCE: "Appendix D. Southern Cuisine—Reduced Calorie," in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, October 2000, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12, 2006) | |||
| Breakfast | |||
| • Oatmeal, prepared with 1% milk, low fat | 1/2 cup | 1/2 cup | |
| • Milk, 1%, low fat | 1/2 cup | 1/2 cup | |
| • English muffin | 1 medium | — | |
| • Cream cheese, light, 18% fat | 1 T | — | |
| • Orange juice | 3/4 cup | 1/2 cup | |
| • Coffee | 1 cup | 1 cup | |
| • Milk, 1%, low fat | 1 oz | 1 oz | |
| Lunch | |||
| • Baked chicken, without skin | 2 oz | 2 oz | |
| • Vegetable oil | 1 tsp | 1/2 tsp | |
| • Salad: | |||
| Lettuce | 1/2 cup | 1/2 cup | |
| Tomato | 1/2 cup | 1/2 cup | |
| Cucumber | 1/2 cup | 1/2 cup | |
| • Oil and vinegar dressing | 2 tsp | 1 tsp | |
| • White rice | 1/2 cup | 1/4 cup | |
| • Margarine, diet | 1/2 tsp | 1/2 tsp | |
| • Baking powder biscuit, prepared with vegetable oil | 1 small | 1/2 small | |
| • Margarine | 1 tsp | 1 tsp | |
| • Water | 1 cup | 1 cup | |
| Dinner | |||
| • Lean roast beef | 3 oz | 2 oz | |
| • Onion | 1/4 cup | 1/4 cup | |
| • Beef gravy, water-based | 1 T | 1 T | |
| • Turnip greens | 1/2 cup | 1/2 cup | |
| • Margarine, diet | 1/2 tsp | 1/2 tsp | |
| • Sweet potato, baked | 1 small | 1 small | |
| • Margarine, diet | 1/2 tsp | 1/4 tsp | |
| • Ground cinnamon | 1 tsp | 1 tsp | |
| • Brown sugar | 1 tsp | 1 tsp | |
| • Corn bread prepared with margarine, diet | 1/2 medium slice | 1/2 medium slice | |
| • Honeydew melon | 1/4 medium | 1/8 medium | |
| • Iced tea, sweetened with sugar | 1 cup | 1 cup | |
| Snack | |||
| • Saltine crackers, unsalted tops | 4 crackers | 4 crackers | |
| • Mozzarella cheese, part skim, low sodium | 1 oz | 1 oz | |
| TABLE 5.7 | |||
|---|---|---|---|
| Sample reduced calorie menus, Asian American cuisine | |||
| 1,600 calories | 1,200 calories | ||
| Calories | 1,609 | Calories | 1,220 |
| Total carbohydrate, % kcals | 56 | Total carbohydrate, % kcals | 55 |
| Total fat, % kcals | 27 | Total fat, % kcals | 27 |
| *Sodium, mg | 1,296 | *Sodium, mg | 1,043 |
| Saturated fat, % kcals | 8 | Saturated fat, % kcals | 8 |
| Cholesterol, mg | 148 | Cholesterol, mg | 117 |
| Protein, % kcals | 20 | Protein, % kcals | 21 |
| 1,600: 100% RDA net for all nutrients except zinc 95%, iron 87%, and calcium 93%. | |||
| 1,200: 100% RDA net for all nutrients except vitamin E 75%, calcium 84%, magnesium 98%, iron 66%, and zinc 77% | |||
| *No salt added in recipe preparation or as seasoning. Consume at least 3 ounces of water. | |||
| SOURCE: "Appendix D. Asian American Cuisine—Reduced Calorie," in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, October 2000, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12, 2006) | |||
| Breakfast | |||
| • Banana | 1 small | 1 small | |
| • Whole wheat bread | 2 slices | 1 slice | |
| • Margarine | 1 tsp | 1 tsp | |
| • Orange juice | 3/4 tsp | 3/4 tsp | |
| • Milk 1%, low fat | 3/4 cup | 3/4 cup | |
| Lunch | |||
| • Beef noodle soup, canned, low sodium | 1/2 cup | 1/2 cup | |
| • Chinese noodle and beef salad: | |||
| Roast beef | 3 oz | 2 oz | |
| Peanut oil | 11/2 tsp | 1 tsp | |
| Soya sauce, low sodium | tsp | 1 tsp | |
| Carrots | 1/2 cup | 1/2 cup | |
| Zucchini | 1/2 cup | 1/2 cup | |
| Onion | 1/4 cup | 1/4 cup | |
| Chinese noodles, soft type | 1/4 cup | 1/4 cup | |
| • Apple | 1 medium | 1 medium | |
| • Tea, unsweetened | 1 cup | 1 cup | |
| Dinner | |||
| • Pork stir-fry with vegetables: | |||
| Pork cutlet | 2 oz | 2 oz | |
| Peanut oil | 1 tsp | 1 tsp | |
| Soya sauce, low sodium | 1 tsp | 1 tsp | |
| Broccoli | 1/2 cup | 1/2 cup | |
| Carrots | 1 cup | 1 cup | |
| Mushrooms | 1/4 cup | 1/2 cup | |
| • Steamed white rice | 1 cup | 1 cup | |
| • Tea, unsweetened | 1 cup | 1 cup | |
| Snack | |||
| • Almond cookies | 2 cookies | — | |
| • Milk 1%, low fat | 1/2 cup | 1/2 cup | |
Measurement of GI is a relatively recent practice. It began during the 1990s, following the discovery that specific carbohydrates such as potatoes and cornflakes raised blood sugar faster than others such as brown rice and oatmeal. Harvard University School of Public Health
TABLE 5.8 Sample reduced calorie menus, Mexican American cuisine
| TABLE 5.8 | |||
|---|---|---|---|
| Sample reduced calorie menus, Mexican American cuisine | |||
| 1,600 calories | 1,200 calories | ||
| Calories | 1,638 | Calories | 1,239 |
| Total carbohydrate, % kcals | 56 | Total carbohydrate, % kcals | 58 |
| Total fat, % kcals | 27 | Total fat, % kcals | 26 |
| *Sodium, mg | 1,616 | *Sodium, mg | 1,364 |
| Saturated fat, % kcals | 9 | Saturated fat, % kcals | 8 |
| Cholesterol, mg | 153 | Cholesterol, mg | 91 |
| Protein, % kcals | 20 | Protein, % kcals | 19 |
| 1,600: 100% RDA met for all nutrients except vitamin in E 97% and Zinc 84% | |||
| 1,200: 100% RDNA met for all nutrients except vitamin E 71%, vitamin B1 & B3 91%, vitamin B2 & iron 90%, and calcium 92%. | |||
| *No salt in recipe preparation or as seasoning. Consume at least 32 ounces of water. | |||
| SOURCE: "Appendix D. Mexican American Cuisine—Reduced Calorie," in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, October 2000, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12, 2006) | |||
| Breakfast | |||
| • Cantaloupe | 1 cup | 1/2 cup | |
| • Farina, prepared with 1% low fat milk | 1/2 cup | 1/2 cup | |
| • White bread | 1 slice | 1 slice | |
| • Margarine | 1 tsp | 1 tsp | |
| • Jelly | 1 tsp | 1 tsp | |
| • Orange Juice | 121 cup | 3/4 cup | |
| • Milk, 1%, low fat | 21 cup | 21 cup | |
| Lunch | |||
| • Beef enchilada: | |||
| Tortilla, corn | 2 tortillas | 2 tortillas | |
| Lean roast beef | 2 1/2 oz | 2 oz | |
| Vegetable oil | 2/3 tsp | 2/3 tsp | |
| Onion | 1 T | 1 T | |
| Tomato | 4 T | 4 T | |
| Lettuce | 1/2 cup | 1/2 cup | |
| Chili peppers | 2 tsp | 2 tsp | |
| Refried beans, prepared with vegetable oil | 1/4 cup | 1/4 cup | |
| • Carrots | 5 sticks | 5 sticks | |
| • Celery | 6 sticks | 6 sticks | |
| • Milk, 1%, low fat | 1/2 cup | — | |
| • Water | — | 1 cup | |
| Dinner | |||
| • Chicken taco: | |||
| Tortilla, corn | 1 tortilla | 1 tortilla | |
| Chicken breast, without skin | 2 oz | 1 oz | |
| Vegetable oil | 2/3 tsp | 2/3 tsp | |
| Cheddar cheese, low fat and low sodium | 1 oz | 1/2 oz | |
| Guacamole | 2 T | 2 T | |
| Salsa | 1 T | 1 T | |
| • Corn, seasoned with | 1/2 cup | 1/2 cup | |
| Margarine | 1/2 tsp | — | |
| • Spanish rice without meat | 1/2 cup | 1/2 cup | |
| • Banana | 1 large | 1/2 large | |
| • Coffee | 1 cup | 1/2 cup | |
| • Milk, 1% | 1 oz | 1 oz | |
researchers used GI to calculate glycemic load—a measure that considers the food's GI and the amount of carbohydrate contained in a single serving. For example, many whole fruits, vegetables, and grains have low glycemic loads, which when consumed prompt a moderate rise in blood glucose and insulin. When the same fruits, vegetables, and grains are squeezed or pulverized into juice or flour, their glycemic load increases—effectively
TABLE 5.9 Sample reduced calorie menus, Lacto-ovo vegetarian cuisine
| TABLE 5.9 | |||
|---|---|---|---|
| Sample reduced calorie menus, Lacto-ovo vegetarian cuisine | |||
| Breakfast | 1,600 calories | 1,200 calories | |
| Calories | 1,650 | Calories | 1,205 |
| Total carbohydrate, % kcals | 56 | Total carbohydrate, % kcals | 60 |
| Total fat, % kcals | 27 | Total fat, % kcals | 25 |
| *Sodium, mg | 1,829 | *Sodium, mg | 1,335 |
| Saturated fat, % kcals | 8 | Saturated fat, % kcals | 7 |
| Cholesterol, mg | 82 | Cholesterol, mg | 44 |
| Protein, % kcals | 19 | Protein, % kcals | 18 |
| 1,600:100% RDA met for all nutrients except vitamin E 92%, vitamin B3 97%, vitamin B6 67%, iron 73%, and zinc 68% | |||
| 1,200:100% RDA met for all nutrients except vitamin E 75%, vitamin B1 92%, vitamin B3 69%, vitamin B659%, iron 54%, and zinc 46%. | |||
| *No salt added in recipe preparation or as seasoning. Consume at least 32 ounces of Water. | |||
| SOURCE: "Appendix D. Lacto-Ovo Vegetarian Cuisine—Reduced Calorie," in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, June 1998, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12, 2006) | |||
| • Orange | 1 medium | 1 medium | |
| • Pancakes, made with 1% lowfat milk and eggs whites | 3 4″ circles | 2 4″ circles | |
| • Pancake syrup | 2T | 1T | |
| • Margarine, diet | 1 1/2 tsp | 1 1/2 tsp | |
| • Milk, 1%, lowfat | 1 cup | 1/2 cup | |
| • Coffee | 1 cup | 1 cup | |
| • Milk, 1%, lowfat | 1 oz | 1 oz | |
| Lunch | |||
| • Vegetable soup, canned, low sodium | 1 cup | 1/2 cup | |
| • Bagel | 1 medium | 1/2 medium | |
| • Processed american cheese, lowfat | 3/4 oz | — | |
| • Spinach salad: | |||
| Spinach | 1 cup | 1 cup | |
| Mushrooms | 1/2cup | 1/2cup | |
| • Salad dressing, regular calorie | 2 tsp | 2 tsp | |
| • Apple | 1 medium | 1 medium | |
| • Iced tea, unsweetened | 1 cup | 1 cup | |
| Dinner | |||
| • Omelette: | |||
| Egg whites | 4 large eggs | 4 large eggs | |
| Green pepper | 2 T | 2T | |
| Onion | 2 T | 2T | |
| Mozzarella cheese, made from part skim milk, low sodium | 1 oz | 1 oz | |
| Vegetable oil | 1 T | 1/2 T | |
| • Brown rice, seasoned with | 1/2cup | 1/2cup | |
| Margarine, diet | 1/2tsp | 1/2tsp | |
| • Carrots, seasoned with | 1/2 cup | 1/2 cup | |
| Margarine, diet | 1/2 tsp | 1/2 tsp | |
| • Whole wheat bread | 1 slice | 1 slice | |
| • Margarine, diet | 1 tsp | 1 tsp | |
| • Fig bar cookie | 1 bar | 1 bar | |
| • Tea | 1 cup | 1 cup | |
| • Honey | 1 tsp | 1 tsp | |
| • Milk, 1%, lowfat | 3/4 cup | 3/4 cup | |
rendering them with the same high glycemic load of sugar water.
After consuming a meal with a high glycemic load, blood sugar rises higher and faster than it does after eating a meal with a low glycemic load. In an effort to recover
TABLE 5.10 Food exchange list
| TABLE 5.10 | |||
|---|---|---|---|
| Food exchange list | |||
| Within each group, these foods can be exchanged for each other. You can use this list to give yourself more choices. | |||
| SOURCE: "Appendix E. Food Exchange List," in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, October 2000, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12, 2006) | |||
| Vegetables contain 25 calories and 5 grams of carbohydrate One serving equals: | Fruits contain 15 grams of carbohydrates and 60 calories One serving equals: | ||
| • 1/2 cup | Cooked vegetables (carrots, broccoli, zucchini, cabbage, etc.) | • 1 small | Apple, banana, orange, nectarine |
| • 1 cup | Raw vegetables or salad greens | • 1 medium | Fresh peach |
| • 1/2 cup | Vegetable juice | • 1 | Kiwi |
| If you're hungry, eat more fresh or steamed vegetables | • 1/2 | Grapefruit | |
| • 1/2 | Mango | ||
| Fat free and very low fat milk contains 90 calories and 12 grams of carbohydrate per serving. One serving equals: | • 1 cup | Fresh berries (strawberries, raspberries, or blueberries) | |
| • 1 cup | Fresh melon cubes | ||
| • 8 oz | Milk, fat free or 1 % fat | • 1/8 | Honeydew melon |
| • 1/4 cup | Yogurt, plain nonfat or low fat | • 4 oz | Unsweetened juice |
| • 1 cup | Yogurt, artificially sweetened | • 4 tsp | Jelly or jam |
| Very lean protein choices have 35 calories and 1 gram of fat per serving. | Lean protein choices have 55 calories and 2 to 3 grams of fat per serving. | ||
| One serving equals: | One serving equals: | ||
| • 1 oz | Turkey breast or chicken breast, skin removed | • 1 oz | Chicken—dark meat, skin removed |
| • 1 oz | Fish fillet (flounder, sole, scrod, cod, haddock, halibut) | • 1 oz | Turkey—dark meat, skin removed |
| • 1 oz | Canned tuna in water | • 1 oz | Salmon, swordfish, herring, catfish, trout |
| • 1 oz | Shellfish (clams, lobster, scallop, shrimp) | • 1 oz | Lean beef (flank steak, London broil, tenderloin, roast beef)* |
| • 3/4 cup | Cottage cheese, nonfat or lowfat | • 1 oz | Veal, roast, or lean chop* |
| • 2 each | Egg whites | • 1 oz | Lamb, roast, or lean chop* |
| • 1/4 cup | Egg substitute | • 1 oz | Pork, tenderloin, or fresh ham* |
| • 1 oz | Fat free cheese | • 1 oz | Lowfat cheese (3 grams or less of fat per ounce) |
| • 1/2 cup | Beans—cooked (black beans, kidney, chickpeas, or lentils): count as 1 starch/bread and 1 very lean protein | • 1 oz | Lowfat luncheon meats (with 3 grams or less of fat per ounce) |
| • 1/4 cup | 4.5% cottage cheese | ||
| • 2 medium | Sardines | ||
| Medium fat proteins have 75 calories and 5 grams of fat per serving | *Limit to 1 to 2 times per week | ||
| One serving equals: | |||
| • 1 oz | Beef (any prime cut), corned beef, ground beef** | Starches contain 15 grams of carbohydrate and 80 calories per serving One serving equals: | |
| • 1 oz | Pork chop | ||
| • 1 eacn | Whole egg (medium)** | • 1 slice | Bread (white, pumpernickel, whole wheat, rye) |
| • 1 oz | Mozzarella cheese | • 2 slice | Reduced calorie or "lite" bread |
| • 1/4 cup | Ricotta cheese | • 1/4 (1 oz) | Bagel (varies) |
| • 4 oz | Tofu (note that this is a heart-healthy choice) | • 1/2 | English muffin |
| **Choose these very infrequently. | • 1/2 | Hamburger bun | |
| • 3/4 cup | Cold cereal | ||
| Fats contain 45 calories and 5 grams of fat per serving One serving equals: | • 1/3 cup | Rice, brown or white—cooked | |
| • 1/3 cup | Barley or couscous—cooked | ||
| • 1 tsp | Oil (vegetable, corn, canola, olive, etc) | • 1/3 cup | Legumes (dried beans, peas, or lentils)—cooked |
| * 1 tsp | Butter | • 1/2 cup | Pasta—cooked |
| • 1 tsp | Stick margarine | • 1/2 cup | Bulgur—cooked |
| • 1 tsp | Mayonnaise | • 1/2 cup | Corn, sweet potato, or green peas |
| • 1 T | Reduced fat margarine or mayonnaise | • 3 oz | Baked sweet or white potato |
| • 1 T | Salad dressing | • 3/4 oz | Pretzels |
| • 1 T | Cream cheese | • 3 cups | Popcorn, hot-air popped or microwave (80-percent light) |
| • 2 T | Lite cream cheese | ||
| • 1/8 | Avocado | ||
| • 8 large | Black olives | ||
| • 10 large | Stuffed green olives | ||
| • 1 slice | Bacon | ||
Proponents of low-carbohydrate diets observe that consuming foods with low glycemic loads stabilizes blood sugar and insulin to prevent the fluctuations that can cause overeating and may increase risk for diabetes. They also assert that reliance on low-fat diets inadvertently led to diets that were high in simple carbohydrates, and indirectly promoted the observed increase in overweight and diabetes in the United States.
Low-Fat Diets
Low-fat diets reduce caloric intake by reducing fat consumption. Fat has nine calories per gram, while protein and carbohydrates have four calories per gram.
TABLE 5.11 Low calorie, lower fat alternatives
| TABLE 5.11 | ||
|---|---|---|
| Low calorie, lower fat alternatives | ||
| Instead of … | Replace with … | |
| SOURCE: "Appendix C. Instead of … Replace with …" in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, October 2000, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12,2006) | ||
|
Dairy products |
|
|
Cereals, grains and pasta |
|
|
Meat, fish, and poultry |
|
| Baked goods |
|
|
|
Snacks and sweets |
|
|
Fats, oils, and salad dressings |
|
|
Miscellaneous |
|
Table 5.11 shows some of the food substitutions that may be made to reduce the dietary fat content. In addition to making substitutions, many fat-free or low-fat food products are available—from fat-free frozen desserts to
TABLE 5.12 Fat free or reduced fat versus regular
| TABLE 5.12 | |||
|---|---|---|---|
| Fat free or reduced fat versus regular | |||
| Fat free or reduced fat | Calories | Regular | Calories |
| SOURCE: "Fat Free or Reduced Fat Versus Regular," in The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, North American Association for the Study of Obesity, October 2000, http://www.nhlbi.nih.gov/guidelines/obesity/practgde.htm (accessed January 12, 2006) | |||
| Reduced fat peanut butter, 2 T | 187 | Regular peanut butter, 2 T | 191 |
| Cookies | Cookies | ||
| Reduced fat chocolate chip cookies, 3 cookies (30 g) | 118 | Regular chocolate chip cookies, 3 cookies (30 g) | 142 |
| Fat free fig cookies, 2 cookies (30 g) | 102 | Regular fig cookies, 2 cookies (30 g) | 111 |
| Ice creams | Ice cream | ||
| Nonfat vanilla frozen yogurt (1% fat), 1/2 cup | 100 | Regular whole milk vanilla frozen yogurt (3-4% fat), 1/2 cup | 104 |
| Light vanilla ice cream (7% fat), 1/2 cup | 111 | Regular vanilla ice cream(11% fat), 1/2 cup | 133 |
| Fat free caramel topping, 2 T | 103 | Caramel topping, homemade with butter, 2 T | 103 |
| Low fat granola cereal, approx, 1/2 cup (55 g) | 213 | Regular granola cereal, approx, 1/2 cup (55 g) | 257 |
| Low fat blueberry muffin, 1 small (2 1/2 inch) | 131 | Regular blueberry muffin, 1 small (2 1/2 inch) | 138 |
| Baked tortilla chips, 1 oz | 113 | Regular tortilla chips, 1 oz. | 143 |
| Low fat cereal bar, 1 bar (1.3 oz.) | 130 | Regular cereal bar, 1 bar (1.3 oz.) | 140 |
Low-Fat versus Low-Carbohydrate Diets
In the absence of rigorous scientific research and studies demonstrating the long-term safety and effectiveness of low-carbohydrate and low-fat diets, many investigators and health professionals hesitate to proclaim one diet's superiority over all others. There is general consensus that while some diets may produce greater initial weight loss, most perform similarly over time.
In "Efficacy and Safety of Low-Carbohydrate Diets: A Systematic Review" (Journal of the American Medical Association, vol. 289, no. 14, April 2003), Dena Bravata and her colleagues from Stanford and Yale Universities reported the results of their analysis of data about diet-induced changes in weight, serum lipids, fasting serum glucose and fasting serum insulin levels, and blood pressure among adults using low-carbohydrate diets. The investigators stated that they undertook the research in response to concerns about low carbohydrates expressed by the American Dietetic Association (ADA) and the American Heart Association (AHA). Both organizations had warned that low-carbohydrate diets may lead to abnormal metabolic functioning that in turn may prompt serious medical consequences, particularly for participants with cardiovascular disease, Type 2 diabetes mellitus, hyperlipidemia, or hypertension. Specifically, it has been cautioned that low-carbohydrate diets cause the accumulation of ketones, which may result in abnormal metabolism of insulin, impaired liver and kidney function, and salt and water depletion that may cause postural hypotension (sudden drop in blood pressure when rising from sitting) as well as fatigue, constipation, and kidney stones. It has also been posited that excessive consumption of animal proteins and fats may promote hyperlipidemia, and that higher dietary protein loads that may impair kidney function.
Not surprisingly, the investigators found that diets that restricted calorie intake and were longer in duration were associated with weight loss. They also observed that when lower-carbohydrate diets resulted in weight loss, it was likely due to the restriction of calorie intake and longer duration rather than changes in carbohydrate intake. The investigators did, however, observe that at least in the short term, low-carbohydrate diets were not associated with the anticipated adverse effects on lipid levels, glucose levels, or blood pressure. Further, their findings suggested that people without diabetes tolerated a lower-carbohydrate diet better than higher-carbohydrate alternatives and that this diet may be an effective means of achieving short-term weight loss without significant adverse effects on serum lipid levels, glycemic control, or blood pressure. They cautioned, however, that there is still inadequate evidence to recommend or condemn the use of low-carbohydrate diets among people with diabetes or for long-term use.
Michael Dansinger and his colleagues at Tufts University, New England Medical Center, compared the effectiveness of four popular diets—Atkins (low carbohydrates), the Zone (moderate carbohydrates), Ornish (low-fat vegetarian), and Weight Watchers (moderate fat). They presented the results of their study, funded by a National Institutes of Health (NIH) grant, the Tufts-New England Medical Center, and the USDA Nutrition Research Center at Tufts, at the scientific sessions of the American Heart Association meeting in November 2003.
Study participants were asked to follow the diets they were given as best they could for two months, and they were given official diet cookbooks and assigned to small group classes for diet education. For the remaining ten months the participants were told to follow their assigned diets "to whatever extent they wanted." The investigators reported that nearly one-quarter of the participants (22%) had dropped out of each diet after just two months, and by twelve months half of the participants assigned to low-carbohydrate or low-fat vegetarian diets had dropped out, as had 35% of participants assigned to the moderate carbohydrates and moderate fat diets. For those participants who adhered, weight loss and reduction in cardiac risk scores as measured by reductions in low-density lipoprotein (LDL cholesterol) and insulin levels were comparable for participants on the low-carbohydrate, moderate-carbohydrate, and moderate-fat plans. According to the study, the Ornish diet (low-fat vegetarian) "was best for lowering 'bad' LDL cholesterol, while other diets were better at raising 'good' HDL cholesterol."
The investigators concluded that their research "demonstrated that all these diets work." They also reiterated the importance of tailoring the selection of a weight-loss diet to ensure adherence, asserting "That means that physicians can work with patients to select the diet that is best suited to the patient. For example, if you have a patient who likes meat, it is unlikely that he or she will comply with the Ornish diet" (American Heart Association Scientific Sessions, Abstract 3535, November 12, 2003).
In "Low-Carb, Low-Fat Diet Gurus Face Off" (Journal of the American Medical Association, vol. 289, no. 14, April 2003), author Joan Stephenson asked the champions of the opposing regimens to offer their opinions about weight-loss approaches and the obesity epidemic. The late Dr. Atkins observed that low-carbohydrate dieters experienced more weight loss and greater improvements in LDL cholesterol and HDL than people on low-fat diets. He explained that while people on his plan consume about 40% of their calories from fat, as opposed to the U.S. average of 30%, the increased fat consumption is not harmful because "When the carbohydrate content is low, the fat takes a different metabolic pathway and forms energy through ketones, which then gets burned up right away. So the ketones do not accumulate because they're being used for energy."
In the same article, Dr. Ornish asserted that the overall health benefits of a low-fat diet were greater because carbohydrates are less calorie dense than protein and fat and that this diet sharply limits consumption of disease-promoting substances such as saturated fat and dietary cholesterol while increasing intake of protective nutrients such as phytochemicals, carotenoids, and lycopene—substances found in fruits, vegetables, grains, beans, and soy products. Ornish also observed that while there is not yet any data indicating that low-carbohydrate diets can reverse coronary heart disease, low-fat diets have been found to not only produce weight loss but also to reverse heart disease as measured by quantitative arteriography (systematic examination of the arteries using an injected contrast material that can be seen using x-ray equipment) and other cardiac imaging studies.
In May 2004, two published studies reaffirmed the safety and efficacy of low-carbohydrate diets. In the first study, 120 study participants were assigned to a low-carbohydrate, high-protein diet or a low-fat, low-cholesterol, low-calorie diet. The low-carbohydrate group was allowed unlimited calories, animal foods (meat, fowl, fish, and shellfish), and eggs, as well as 4 ounces of hard cheese, two cups of salad vegetables (lettuce, spinach, or celery) and one cup of low-carbohydrate vegetables (broccoli, cauliflower, or squash). The low-fat, low-cholesterol, low-calorie group consumed less than 30% of daily caloric intake from fat, less than 10% of calories from saturated fat, and less than 300 mg cholesterol daily. After six months, weight loss was greater in the low-carbohydrate diet group than in the low-fat diet group. Compared with the low-fat diet group, the low-carbohydrate diet group had greater decreases in serum triglyceride levels and greater increases in HDL cholesterol levels (William Yancy Jr. et al., "A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet to Treat Obesity and Hyperlipidemia: A Randomized, Controlled Trial," Annals of Internal Medicine, vol. 140, no. 10, May 18, 2004).
In the second study, researchers assigned 132 obese adults to either restrict carbohydrate intake to less than 30 g per day (low-carbohydrate diet) or to restrict caloric intake by 500 calories per day with less than 30% of calories from fat (conventional diet). After one year, weight loss was greater in the low-carbohydrate diet group, and the researchers found that the low-carbohydrate diet group fared better in terms of greater decrease in triglyceride levels (Linda Stern et al., "A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet to Treat Obesity and Hyperlipidemia: A Randomized, Controlled Trial," Annals of Internal Medicine, vol. 140, no. 10, May 18, 2004).
In October 2004 yet another study confirmed that modified low carbohydrate diets produced greater weight loss than the U.S. National Cholesterol Education Program (NCEP) diet, which replaces saturated fat with carbohydrates (Y. W. Aude et al., "The National Cholesterol Education Program Diet vs. a Diet Lower in Carbohydrates and Higher in Protein and Monounsaturated Fat: A Randomized Trial," Archives of Internal Medicine, vol. 164, no. 19, October 25, 2004).
The following month, however, Suzanne Phelan, a researcher from Brown Medical School asserted that low-fat diets produce better long-term weight loss than low-carbohydrate diets at a meeting of the North American Association for the Study of Obesity. She and her colleagues studied 2,700 people who entered the National Weight Control Registry, which records successful efforts to lose at least thirty pounds and maintain the loss for at least one year. All of the subjects reported eating about 1,400 calories a day, but the portion derived from fat rose from 24% in 1995 to more than 29% in 2003, while the portion from carbohydrates fell, from 56% to 49% The number who were on low-carbohydrate diets (less than 90 grams a day) rose from 6% to 17% during the same period.
Although the type of diet—low-fat or low-carbohydrate—made no difference in how people lost weight initially, those who increased their fat intake over a year regained the most weight. The researchers concluded that they ate fewer carbohydrates, since the amount of protein in their diets remained the same. The researchers concluded that the minority of successful dieters use low-carbohydrate regimes.
While there is no single winner in the diet wars, further research has dispelled some fears about the safety and effectiveness of the low-carbohydrate diet. Low-carbohydrate diets appear to be safe and effective in the short term, but long-term outcomes still are unclear. Although some results suggest that higher protein and fat intakes lead to lower total caloric intake by producing earlier satiety, these diets have not been shown to alter fundamental eating behaviors nor have they demonstrated, as many of their proponents argue, the ability to modify caloric balance such that weight loss persists when more calories are consumed than expended.
Finally, research published in the Journal of the American Medical Association in January 2005 asserted that adherence to a diet for one year, rather than the specific type of diet, is the single most important determinant of weight loss and reduction of risk of cardiovascular disease. The investigators found the amount of weight lost was associated with the level of dietary adherence but not with diet type, and they concluded that, "One way to improve dietary adherence rates in clinical practice may be to use a broad spectrum of diet options, to better match individual patient food preferences, lifestyles, and cardiovascular risk profiles. Our findings challenge the concept that one type of diet is best for everybody and that alternative diets can be disregarded. Likewise, our findings do not support the notion that very low carbohydrate diets are better than standard diets, despite recent evidence to the contrary" (Michael Dansinger et al., "Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease Risk Reduction: A Randomized Trial," Journal of the American Medical Association, vol. 293, no.1, January 5, 2005).
In an accompanying editorial, Robert H. Eckel, a physician from the University of Colorado at Denver, commented that, "It seems plausible that for maintenance of reduced body mass, the right diet needs to be matched with the right patient" He advised a "low fad" approach for people dieting to lose weight ("The Dietary Approach to Obesity: Is It the Diet or the Disorder?" Journal of the American Medical Association, vol. 293, no.1, January 5, 2005).
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