Patients who are obese walk into physician offices every day; according to one study, approximately 33 percent of U.S. adults are obese and 66 percent are overweight.¹ Overweight or obesity is their primary medical complaint, or it is present in addition to another health problem. As discussed by Dr. Rao in this issue of American Family Physician,² obesity is a chronic, relapsing, stigmatized, and costly medical disease with long-term consequences,³ and it deserves to be treated seriously.^4,5 Obesity is caused mainly by too much food intake over an extended period of time⁶; any decline in physical activity is less important.⁷ If the problem is too many calories, then the preventive strategies should focus on ways to reduce calories acutely for weight loss and chronically to slow relapse.

One strategy is to reduce caloric intake from beverages that typically contain no nutrients other than sugar or high-fructose corn syrup. There is convincing evidence that soft drink consumption is related to energy intake and weight gain,⁸ and reducing that consumption is part of my approach to weight loss.⁹ Soft drink intake is also related to an increased risk of diabetes mellitus, cardiovascular disease, and gout.⁸

My advice to patients about weight loss is based on information from the Diabetes Prevention Program¹⁰ and the Look AHEAD trial,¹¹ two long-term studies on the prevention of diabetes and its complications, funded by the National Institutes of Health. In the Diabetes Prevention Program, diets that were lower in calories and fat, coupled with individual lifestyle counseling, produced a 7 percent weight loss and reduced the risk of diabetes by 58 percent among patients with impaired glucose tolerance.¹⁰ When meal replacements were added to a similar lifestyle program among patients who had diabetes, the weight loss was even larger at 8.5 percent.¹¹ This improvement, along with results of a meta-analysis of meal replacement strategies,¹² suggests that overweight patients should be encouraged to use meal replacements/portion-controlled diets (i.e., foods with calories that are appropriate for the patient's age and size identified on the package).

In the Look AHEAD trial, which also involved patients with diabetes, weight loss at one year was directly related to the number of meal replacements that participants used—more was better.¹³ A large randomized clinical trial compared diets consisting of 15 versus 25 percent protein; 20 versus 40 percent fat; and 65, 55, 45, and 35 percent carbohydrates.¹⁴ It showed that diet composition had similar effects on weight loss over two years. Replacing one or two of the meals with portion-controlled foods such as frozen meals, canned shakes, and nutrition bars can help patients lose weight if they adhere to the diet.

Increased physical activity, diets lower in fat, and regular weigh-ins are important in helping patients who lose weight to maintain that loss. Simply using a pedometer to count the number of steps taken per day and a bathroom scale for daily weighing can be useful. In one systematic review, use of pedometers significantly increased weight loss¹⁵; self-weighing helps to maintain weight loss.¹⁶

Patients who are obese often have a number of health problems in addition to excess weight. For those with depression, bupropion (Wellbutrin) may be a more appropriate treatment than another antidepressant that can produce weight gain.¹⁷ For patients with migraine, topiramate (Topamax) is a drug approved by the U.S. Food and Drug Administration (FDA) that also can produce modest weight loss.¹⁸ Metformin (Glucophage) has been shown to reduce the risk of diabetes and to produce modest long-term weight loss in patients at high risk of diabetes or who have early diabetes.¹⁹ Exenatide (Byetta), a drug currently approved by the FDA for the treatment of diabetes, produces modest weight loss in some patients, which is better than the weight gain that often occurs with other antidiabetic drugs. Liraglutide (Victoza), another antidiabetic glucagon-like peptide–1 agonist, has been approved to treat diabetes. In a clinical trial of patients without diabetes, liraglutide was shown to produce significant dose-dependent weight loss.²⁰

Pramlintide (Symlin), an FDA-approved antidiabetic drug, has been tested in combination with sibutramine (Meridia) or phentermine (Adipex) in human clinical trials and shown to produce weight loss in modestly obese patients.²¹ Another study combined FDA-approved weight-loss drugs with behavioral therapy in patients who were very obese (i.e., body mass index of 40 to 60 kg per m²) treated by primary care physicians, with weight losses of up to 16 percent of baseline in one year.²² Patients maintained much of this loss for a second year if they adhered to the program.

Thus, there is reason for family physicians to treat obesity as a serious condition and counsel patients who are overweight and obese on how to achieve weight loss through reduced consumption of sugar-sweetened soft beverages, use of meal replacements and portion control, increased physical activity, pharmacotherapy, and even behavioral therapy, when indicated.