Therapy
The mainstay of treatment for obesity is an energy-limited diet and increased exercise. In studies, diet and exercise programs have consistently produced an average weight loss of approximately 8% of total body mass (excluding study drop-outs). While not all dieters will be satisfied with this outcome, studies have shown that a loss of as little as 5% of body mass can create large health benefits. A more intractable therapeutic problem appears to be weight loss maintenance. Of dieters who manage to lose 10% or more of their body mass in studies, 80-95% will regain that weight within two to five years, supporting the finding that the body has various mechanisms that maintain weight at a certain set point.[citation needed]
In a clinical practice guideline by the American College of Physicians, the following five recommendations are made:[29]
People with a BMI of over 30 should be counseled on diet, exercise and other relevant behavioral interventions, and set a realistic goal for weight loss.
If these goals are not achieved, pharmacotherapy can be offered. The patient needs to be informed of the possibility of side-effects and the unavailability of long-term safety and efficacy data.
Drug therapy may consist of sibutramine, orlistat, phentermine, diethylpropion, fluoxetine, and bupropion. For more severe cases of obesity, stronger drugs such as amphetamine and methamphetamine may be used on a selective basis. Evidence is not sufficient to recommend sertraline, topiramate, or zonisamide.
In patients with BMI > 40 who fail to achieve their weight loss goals (with or without medication) and who develop obesity-related complications, referral for bariatric surgery may be indicated. The patient needs to be aware of the potential complications.
Those requiring bariatric surgery should be referred to high-volume referral centers, as the evidence suggests that surgeons who frequently perform these procedures have fewer complications.
A clinical practice guideline by the US Preventive Services Task Force (USPSTF) concluded that the evidence is insufficient to recommend for or against routine behavioral counseling to promote a healthy diet in unselected patients in primary care settings, but that intensive behavioral dietary counseling is recommended in those with hyperlipidemia and other known risk factors for cardiovascular and diet-related chronic disease. Intensive counseling can be delivered by primary care clinicians or by referral to other specialists, such as nutritionists or dietitians.[30][31]
Counseling
A meta-analysis of randomized controlled trials concluded that "compared with usual care, dietary counseling interventions produce modest weight losses that diminish over time."[32]
Diets
Various dietary approaches have been proposed, some of which have been compared by randomized controlled trials:
A comparison of Dr Atkins' diet, Slim-Fast plan, Weight Watchers "pure points programme", and Rosemary Conley's found no significant differences.[33]
A comparison of Atkins diet, Zone diet, Weight Watchers, and Ornish diet noted:[34]
"all 4 diets resulted in modest statistically significant weight loss at 1 year, with no statistically significant differences between diets"
"The higher discontinuation rates for the Atkins and Ornish diet groups suggest many individuals found these diets to be too extreme"
Low carbohydrate versus low fat
Many studies have focused on diets that reduce calories via a low-carbohydrate (Atkins diet, Zone diet) diet versus a low-fat diet (LEARN diet, Ornish diet). The Nurses' Health Study, an observational cohort study, found that low carbohydrate diets based on vegetable sources of fat and protein are associated with less coronary heart disease.[35]
A meta-analysis of randomized controlled trials by the international Cochrane Collaboration in 2002 concluded[36] that fat-restricted diets are no better than calorie restricted diets in achieving long term weight loss in overweight or obese people.
A more recent meta-analysis that included more recent randomized controlled trials[37][38][34] found that "low-carbohydrate, non-energy-restricted diets appear to be at least as effective as low-fat, energy-restricted diets in inducing weight loss for up to 1 year. However, potential favorable changes in triglyceride and high-density lipoprotein cholesterol values should be weighed against potential unfavorable changes in low-density lipoprotein cholesterol values when low-carbohydrate diets to induce weight loss are considered."[39]
The Women's Health Initiative Randomized Controlled Dietary Modification Trial[40] found that a diet of total fat to 20% of energy and increasing consumption of vegetables and fruit to at least 5 servings daily and grains to at least 6 servings daily:
no reduction in cardiovascular disease[41]
an insignificant reduction in invasive breast cancer[42]
no reductions in colorectal cancer[43]
Additional recent randomized controlled trials have found that:
A comparison of Atkins, Zone diet, Ornish diet, and LEARN diet in premenopausal women found the greatest benefit from the Atkins diet.[44]
The best diet may be influenced by measured insulin secretion:
In young adults "Reducing glycemic [carbohydrate] load may be especially important to achieve weight loss among individuals with high insulin secretion."[45] This is consistent with prior studies of diabetic patients in which low carbohydrate diets were more beneficial.[46][47]
Low glycemic index
"The glycaemic index factor is a ranking of foods based on their overall effect on blood sugar levels. Low glycaemic index foods, such as lentils, provide a slower more consistent source of glucose to the bloodstream, thereby stimulating less insulin release than high glycaemic index foods, such as white bread."[48][49]
The glycemic load is "the mathematical product of the glycemic index and the carbohydrate amount".[50]
In a randomized controlled trial that compared four diets that varied in carbohydrate amount and glycemic index found complicated results[51]:
Diet 1 and 2 were high carbohydrate (55% of total energy intake)
Diet 1 was high-glycemic index
Diet 2 was low-glycemic index
Diet 3 and 4 were high protein (25% of total energy intake)
Diet 3 was high-glycemic index
Diet 4 was low-glycemic index
Diets 2 and 3 lost the most weight and fat mass; however, low density lipoprotein fell in Diet 2 and rose in Diet 3. Thus the authors concluded that the high-carbohydrate, low-glycemic index diet was the most favorable.
A meta-analysis by the Cochrane Collaboration concluded that low glycemic index or low glycemic load diets led to more weight loss and better lipid profiles. However, the Cochrane Collaboration grouped low glycemic index and low glycemic load diets together and did not try to separate the effects of the load versus the index.[48]
Exercise
A meta-analysis of randomized controlled trials by the international Cochrane Collaboration found that "exercise combined with diet resulted in a greater weight reduction than diet alone".[52]
Drugs
Main article: Anti-obesity drug
A meta-analysis of randomized controlled trials by the international Cochrane Collaboration concluded that in diabetic patients found:[53]
"Fluoxetine, orlistat, and sibutramine can achieve statistically significant weight loss over 12 to 57 weeks. The magnitude of weight loss is modest, however, and the long-term health benefits remain unclear. The safety of sibutramine is uncertain. There is a paucity of data on other drugs for weight loss or control in persons with type 2 diabetes."
Medication most commonly prescribed for diet/exercise-resistant obesity is orlistat (Xenical, which reduces intestinal fat absorption by inhibiting pancreatic lipase) and sibutramine (Reductil, Meridia, an anorectic). In the presence of diabetes mellitus, there is evidence that the anti-diabetic drug metformin (Glucophage) can assist in weight loss—rather than sulfonylurea derivatives and insulin, which often lead to further weight gain. The thiazolidinediones (rosiglitazone or pioglitazone) can cause slight weight gain, but decrease the "pathologic" form of abdominal fat, and are therefore often used in obese diabetics.
Bariatric surgery
Main article: bariatric surgery
Bariatric surgery (or "weight loss surgery") is the use of surgical interventions in the treatment of obesity. As every surgical intervention may lead to complications, it is regarded as a last resort when dietary modification and pharmacological treatment have proven to be unsuccesful. Weight loss surgery relies on various principles; the most common approaches are reducing the volume of the stomach, producing an earlier sense of satiation (e.g. by adjustable gastric banding and vertical banded gastroplasty) while others also reduce the length of bowel that food will be in contact with, directly reducing absorption (gastric bypass surgery). Band surgery is reversible, while bowel shortening operations are not. Some procedures can be performed laparoscopically. Complications from weight loss surgery are frequent.[54]
Two large studies have demonstrated a mortality benefit from bariatric surgery. A marked decrease in the risk of diabetes mellitus, cardiovascular disease and cancer.[55][56] Weight loss was most marked in the first few months after surgery, but the benefit was sustained in the longer term. In one study there was an unexplained increase in deaths from accidents and suicide that did not outweigh the benefit in terms of disease prevention. Gastric bypass surgery was about twice as effective as banding procedures.[56]
