Successful weight-loss treatments generally result in reduced blood pressure, reduced triglycerides, increased HDL cholesterol, and reduced total cholesterol and LDL cholesterol. Weight loss of as little as 5 to 10 percent of initial weight produces measurable health benefits and may prevent illnesses among persons at risk. These findings suggest that treatment should not exclusively focus on the medical consequences of obesity, but obesity itself should be treated. The NIH recommends weight loss for persons with BMI greater than 30 and for those with BMI greater than 25 with two or more obesity-related risk factors. The NIH guidelines recommend that for persons with BMI between 25 and 30 without other risk factors, the focus should be prevention of further weight gain, rather than weight loss.

In "Obesity: What Mental Health Professionals Need to Know," Devlin reported that critics cite the health and psychological risks of "weight cycling"—continuously pursuing weight loss in the diet–weight loss/weight regain cycle known as "yo-yo dieting" as even greater than the risks associated with obesity. They assert that multiple unsuccessful efforts to lose weight demoralize people, make future weight loss even more challenging, and that dietary treatment of obesity may trigger or worsen binge eating among persons who are obese. They also offer several studies that have found an association between weight cycling and increased morbidity and mortality as evidence of the dangers of dieting.

In "Screening and Interventions for Obesity in Adults: Summary of the Evidence for the U.S. Preventive Services Task Force" (Annals of Internal Medicine, vol. 139, no. 11, December 2003), Kathleen McTigue and her colleagues also reviewed the studies that revealed a link between weight cycling and mortality. The investigators found that some studies failed to distinguish between intentional and unintentional weight loss. In the research considering the relationship between weight cycling with intentional weight loss, some studies have found unfavorable effects on coronary heart disease and its risk factors and others have not. They also found data suggesting that weight-cycling risk increases inversely with BMI—the higher the BMI, the lower the risk of weight cycling. If these findings are correct, then persons suffering from obesity as opposed to overweight are at less risk of morbidity and mortality attributable to weight cycling.