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Diet and Myths Weight-Loss Lore and Controversies - Diet And Weight-loss Myths

fat exercise low diets

It is impossible to recount all of the fantastic and improbable claims that have been made in recent years. This section considers some of the most persistent myths about diet, exercise, and weight loss.

Low-Carb Diets

MYTH.

A low-carbohydrate diet is the fastest, healthiest, best way to lose weight.

FACTS.

Low-carbohydrate diets initially may produce more rapid weight loss than other diets; however, most of the loss is water weight rather than fat. The water loss occurs as the kidneys flush out the excess waste products resulting from digestion of protein and fat. Many low-carbohydrate diets encourage consumption of high-fat foods, such as butter, heavy cream, bacon, and cheese. Long-term, high-fat diets may raise blood cholesterol levels, and low-carbohydrate, high-protein diets produce a state of "ketosis" (the accumulation of ketones from partly digested fats as a result of inadequate carbohydrate intake), which may increase the risk of gout (a severe arthritis attack that occurs in one joint—typically the big toe, ankle, or knee—caused by defects in uric acid metabolism) and kidney stones. Further, most nutritionists and researchers concur that while some weight-loss diets are nutritionally inadequate and others are even dangerously insufficient, nearly all diets can affect weight loss, and currently, no compelling evidence exists to proclaim one diet vastly superior to another. A key factor in the success of any weight-loss diet is adherence—whether dieters can remain faithful to the regimen they have chosen, and to date, low-carbohydrate diets have not demonstrated superiority in terms of adherence. Boredom and frustration with a low-carbohydrate regimen may occur when dieters crave the carbohydrates that they are forbidden or can eat only in very small amounts. In a first-person account of low-carbohydrate dieting, "Low-Carb Fast-Food Dinner Leads to Bun Envy" (Sacramento Bee, February 1, 2004), journalist Anita Creamer lamented that "Lettuce is not a bun. And low carb, the diet craze du jour, is not a lifestyle to be embraced by the faint of heart, or by the hungry." She also posited that carbohydrate deprivation may lead to crankiness or moodiness, observing that "low carb partly accounts for the gnawing, low-level unhappiness of women in the 1950s and 1960s. Baby boomers' mothers were always on diets, trying to fit into slender pedal pushers and dresses with nipped waistlines. For weeks on end, they starved themselves on hamburger patties, boiled eggs and iceberg lettuce, and for exercise, they flew into ketonic rages." Creamer's account confirms what nutritionists and obesity researchers have long known—that diets will not work unless people stick to them.

Calorie Reduction

MYTH.

You need to cut calories drastically to lose weight.

FACTS.

Weight loss may be accomplished with modest reductions in calorie consumption. Low-calorie diets often result in metabolic adaptations, such as a significant reduction in resting metabolic rate, which may produce weight maintenance or even weight gain rather than the desired weight loss. Many nutritionists and diet plans advise simultaneously reducing total caloric-intake and modifying the balance of macronutrients (nutrients that the body uses in relatively large amounts—proteins, carbohydrates, and fats)—some weight-loss diets reduce fat intake, others reduce carbohydrates.

Negative-Calorie Foods

MYTH.

It takes more calories to eat and digest some foods such as celery or cabbage than these foods contain and as a result, eating them causes or speeds weight loss.

FACTS.

There are no foods that when eaten cause weight loss. Foods containing caffeine may temporarily boost metabolism but they do not cause weight loss. However, some recent evidence suggests that eating grapefruit or drinking grapefruit juice may help people who are obese to lose weight. Ken Fujioka and his colleagues at the Scripps Clinic in San Diego, California, compared weight loss over a twelve-week period among 100 obese individuals. One third of the subjects ate half a grapefruit before each meal three times a day, while another drank a glass of grapefruit juice before every meal. The third group did not include grapefruit in their meals. In "Grapefruit Diet Works and May Prevent Diabetes" (Chemistry & Industry, No. 3, February 2004), the researchers reported that after twelve weeks, subjects who ate grapefruit lost an average of 3.6 pounds, and those who drank grapefruit juice lost an average of 3.3 pounds while those in the control group who consumed no grapefruit lost an average of 0.5 pounds. The researchers attributed the weight loss to lowered levels of insulin, which were confirmed by measurements of blood glucose and insulin levels. They posited that the more efficiently sugar is metabolized, the less likely it is to be stored as fat. Further, lowering insulin levels reduces feelings of hunger—elevated insulin levels stimulate the brain's hypothalamus, producing feelings of hunger.

Eating at Night

MYTH.

Eating after 8:00 P.M. causes weight gain.

FACTS.

Weight gain or loss does not depend on the time of day food is consumed—excess calories will be stored as fat whether they are consumed mid-morning or just before bedtime. In general, weight is governed by the amount of food consumed measured in total calorie count, and the amount of physical activity expended during the day.

Natural Weight-Loss Products

MYTH.

Organic, natural, or herbal weight-loss products are safer than synthetic (produced in the laboratory) over-the-counter or prescription drugs.

FACTS.

Simply because products are organic or naturally occurring does not necessarily mean that they are risk-free or safe. For example, in July 2003 the Federal Trade Commission (FTC) took action against marketers of weight-loss products containing ephedra, which is derived from a leafless desert shrub, and hydroxycitric acid, which is an extract from brindall berries. The actions targeted deceptive effectiveness, safety, and side-effect claims for weight-loss supplements containing these dietary supplements. The FTC challenged advertising claims that the ephedra and other natural supplements caused rapid, substantial, and permanent weight loss without diet or exercise, as well as the claims that these weight-loss products are "100 percent safe," "perfectly safe," or have "no side effects."

Low-Fat Foods

MYTH.

"Low fat" or "no fat" means few or no calories.

FACTS.

A low-fat or nonfat food is usually lower in calories than the same size—as measured by weight—portion of the full-fat food; however, a food product can contain 0 grams of fat and still have a high calorie content. Many fat-free foods replace the fat with sugar and contain just as many or more calories as full-fat versions. While most fruits and vegetables are naturally low in fat and calories, processed low-fat or nonfat foods may be high in calories because extra sugar, flour, or starch thickeners have been added to enhance the low-fat foods' taste or texture.

Eliminating Starchy Foods

MYTH.

Pasta, potatoes, and bread are fattening foods and should be eliminated or sharply limited when trying to lose weight.

FACTS.

Potatoes, rice, pasta, bread, beans, and some starchy vegetables such as squash, yams, sweet potatoes, turnips, beets, and carrots are not innately fattening. They are rich in complex carbohydrates, which are important sources of energy. Further, foods that are high in complex carbohydrates are often low in fat and calories since carbohydrates contain only 4 calories per gram compared to the 9 calories per gram contained by fats. In "Effects of an Ad Libitum Low-Fat, High-Carbohydrate Diet on Body Weight, Body Composition, and Fat Distribution in Older Men and Women: A Randomized Controlled Trial" (Archives of Internal Medicine, vol. 164, no. 2, January 26, 2004), Nicholas Hays and his colleagues reported the results of a small study that found that dieters lost substantial amounts of weight on a high-carbohydrate, low-fat regimen. Meals were prepared for the subjects, who were told to eat as much as they wanted and to return any uneaten food, which enabled the researchers to calculate the subjects' calorie intake. Surprisingly, subjects who consumed a high-carbohydrate, low-fat diet with no quantity or caloric restrictions lost significant amounts of weight. The researchers speculated that low-fat, high-carbohydrate diets may reduce body weight via reduced food intake, since complex carbohydrate-rich foods are more satiating and less energy-dense than higher-fat foods and concluded that their "data support the alteration of dietary macronutrient composition without emphasis on caloric restriction as an effective means of promoting weight loss."

Genetic Destiny

MYTH.

People from families where many members are overweight or obese are destined to become overweight.

FACTS.

It is true that studies of families have found similarities in body weight and that immediate relatives of obese people are at increased risk for overweight and obesity compared to persons with normal-weight family members. Although it is generally accepted that genetic susceptibility or predisposition to overweight or obesity is a factor, researchers believe that environmental and behavioral factors make equally strong, if not stronger, contributions to the development of obesity. As a result, persons from overweight or obese families may have to make concerted efforts to maintain healthy body weights and prevent weight gain, but they are not destined to become obese simply by virtue of the genes they inherited.

Exercise Alone

MYTH.

Exercise is a better way to lose weight than dieting.

FACTS.

While there are numerous health benefits from exercise, weight loss is not generally considered a direct benefit. Research has consistently demonstrated that for weight loss, diet trumps exercise because it is simpler to reduce caloric intake significantly through diet than to increase caloric expenditure significantly through exercise. For example, if a 155-pound person wished to reduce his or her consumption by 400 calories per day, it might be achieved by simply eliminating dessert and reducing portion sizes. In contrast, expending 400 calories requires considerable effort. To burn 400 calories, a 155-pound person would have to spend about an hour bicycling at about ten miles an hour, playing basketball, hiking cross country, mowing the lawn, ice skating at nine miles per hour or less, water skiing, or walking uphill at about 3.5 miles per hour. However, many studies have demonstrated that exercise is an important way to prevent overweight and maintain weight loss.

Cris Slentz and his colleagues at Duke University Medical Center found that as little as thirty minutes of walking daily is enough exercise to prevent weight gain for most sedentary people, and exertion above that may even cause weight and fat loss. In "Effects of the Amount of Exercise on Body Weight, Body Composition, and Measures of Central Obesity: STRRIDE—A Randomized Controlled Study" (Archives of Internal Medicine, vol. 164, no. 1, January 12, 2004), the investigators reported the results of their study in which 182 overweight, inactive adults aged forty to sixty-five were randomly assigned to one of three programs of escalating exercise or to a control group that did not exercise for eight months. One group did the equivalent of twelve miles of walking per week, another completed the equivalent of twelve miles of jogging per week, and the most intense exercise group performed exercise comparable to jogging twenty miles per week. All of the exercise was performed on treadmills, elliptical trainers, or stationary bicycles in supervised settings. The subjects were encouraged not to change their diets during the study.

Subjects in the two low-level exercise groups lost weight and fat, and those in the most intense exercise program lost more weight and fat than the others. The vigorous exercise group had a 3.5 percent weight loss, the two low-dose groups had slightly more than a 1 percent weight loss, while the control group had a 1.1 percent weight gain. Exercise dose and intensity also determined changes in waist circumference—subjects who did not exercise had a 0.8 percent increase in waist circumference. The two groups doing the lower amounts of exercise had decreases of about 1.5 percent, and the most intensely exercising group reported a waist decline of 3.4 percent. The investigators determined that a modest amount of exercise—thirty minutes a day—can prevent weight gain without changes in diet.

Exercisers' Diets

MYTH.

People who exercise have healthier diets than those who don't work out.

FACTS.

It is a common misconception that by simply embarking on an exercise program people spontaneously improve their diets and make healthier food choices. Although starting to exercise regularly represents a commitment to improved health and wellness, and diet and exercise resolutions are often made together, a recent study revealed that exercisers do not necessarily "eat better." In "Effects of 16 Months of Verified, Supervised Aerobic Exercise on Macronutrient Intake in Overweight Men and Women: The Midwest Exercise Trial" (American Journal of Clinical Nutrition, vol. 78, no. 5, November 2003), Joseph Donnelly and his colleagues from the Center for Physical Activity and Weight Management, Energy Balance Laboratory, and the Department of Dietetics and Nutrition of the University of Kansas, and the Department of Pediatrics at the University of Colorado Health Sciences Center, questioned whether moderate aerobic exercise led to changes in diet, specifically, an increased carbohydrate intake and decreased fat consumption. The investigators assigned seventy-four sedentary, overweight to moderately obese people aged seventeen to thirty-five to one of two groups. The first group engaged in supervised moderate-intensity exercise for forty-five minutes per day, five days a week, and was advised to maintain their usual caloric intake. The other group was told simply to maintain their usual level of physical activity and caloric intake. After sixteen months the investigators found no significant differences between the groups in terms of fat, carbohydrate, or protein intake. The investigators also reported that the exercisers mistakenly believed that "they could eat what they wanted as long as they were exercising."

Eating Disorders

MYTH.

Eating disorders occur exclusively among middle- and upper-class white females.

FACTS.

Like many myths about diet, weight, and nutrition, this one is based on fact—an estimated 90 percent of persons with anorexia nervosa or bulimia nervosa are female; however, according to Susan Yanovski, "Eating Disorders, Race, and Mythology" (Archives of Family Medicine, vol. 9, no. 1, January 2000), binge-eating disorder occurs in both genders and across socioeconomic classes. Yanovski attributes the myth that eating disorders are limited to middle- and upper-class white women to the fact that many studies were conducted on college campuses where few minority students were enrolled, and other research looked at persons seeking treatment, often at referral centers. Yanovski observed that "studies done on such populations, which may be more likely to be white and of higher socioeconomic status, have limited generalizability." She also cited research that found that minorities are substantially affected by eating disorders—one study found that found that African-American women were as likely as white women to report binge eating. Another revealed that the prevalence of binge eating was comparable among Hispanic, non-Hispanic white, and African-American women, but that binge-eating symptoms were more severe among the Hispanic group. Yanovski concluded that "Recognition that eating disorders are color-blind can ensure that appropriate recognition and treatment are available to all patients at risk."

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