Presenter: Donald Kirby, MD, Director, Cleveland Clinic Center for Human Nutrition
Dr. Kirby began his presentation with the much-lamented statistics on obesity in the U.S. and the industrialized world. Prevalence for overweight (BMI 24.9 to 29.9) and obesity (BMI > 30) have been steadily rising for the past 30 years—two-thirds of Americans now qualify as overweight or heavier. Hypertension, hyperlipidemia, coronary artery disease, type 2 diabetes, sleep apnea, and GERD prevalence are following this epidemic. Obesity is now the second most common preventable cause of death, exceeded only by smoking.
Frustrated primary care physicians hoping for breakthroughs in obesity treatment would not have found solutions at ACG 2011. Lacking new therapies, there continue to be only two tried-and-true ways to alter the natural history of obesity… decreased energy intake, and/or increased energy expenditure. Research into the leptin satiety-signaling pathway (between adipocytes and the hypothalamus) has not yet borne fruit. Primary care providers are left with dietary options, including:
1. Portion-controlled, balanced low-calorie diets:
2. Low carbohydrate diets
3. Low-fat diets
4. Fad diets
Limited data exist on the long-term superiority of any particular diet. The Women’s Health Initiative Dietary Modification Trial suggests that low fat diets may be easier to continue over many years than low-carbohydrate diets, which are marked by poor long-term compliance.
Balanced, low-carbohydrate, and low-fat diets have all been shown to reduce weight in the short term. One well-performed trial has shown that the proportion of fat to carbohydrate is less important than whether dieters successfully reduce calories, but there is no value in reducing intake below 800 kcal/d.
Fad diets have little scientific evidence to support their use, and often promote unrealistic weight loss goals. In more reasonable approaches, weight loss of 10% is considered realistic, and 15% is considered excellent. Key predictors of long-term weight loss from the National Weight Control Registry are:
1. Weekly weight measurement
2. Low calorie, low fat diet
3. Breakfast consumption
4. Increased activity: exercise is the best predictor of long-term weight loss
Pharmacotherapy continues to attract research dollars and patient interest, given the limitations of the diet-only approach. Over-the-counter supplements are commonly used, but little evidence supports their efficacy or safety. Current FDA-approved medications for weight loss include diethylpropion (Tenuate), phendimetrazine (Bontril), phentermine, and orlistat (Xenical). Sibutramine was withdrawn in October of 2010 following reports of increased cardiovascular events. None of these medications has been studied for longer than 4 years (in the case of orlistat). Medications commonly used for obesity off-label have not been carefully studied in this context; these include bupropion, topiramate, zonisamide, metformin, pramlintide, liraglutide, and exenatide. Pharmacologic therapy is an option for highly motivated patients with a BMI above 30, who have been unsuccessful through diet and exercise alone.
Dr. Kirby briefly touched on endoscopic procedures that may replace bariatric surgery in the future. Non-surgical techniques have been under study since the 1980s, including an intra-gastric balloon that won FDA approval but was removed from the market. Three endoscopic techniques are currently under study and await further clinical trials and FDA approval:
1. The Bard EndoCinch Suturing System (Bard Davol, Murray Hill, NJ), has been used for GERD but may have a future application for endoluminal vertical gastroplasty in obesity.
2. The TOGA System (Satiety Inc., Palo Alto, CA), an endoscopic stapling system.
3. The duodenal-jejunal bypass sleeve (DJBS): Drawbacks include the need for general anesthesia and fluoroscopy, and about 20% of patients in pilot studies could not tolerate the sleeve and required its removal. But those entering the pilot study lost 22% of their excess weight compared with a control group.
Barring FDA approval for less invasive techniques, bariatric surgery remains the only option for patients with a BMI above 40, or above 35 with obesity-related comorbidities. In the hands of an experienced bariatric surgeon, this can be effective, but the procedure utility is limited by persistent concerns about the morbidity and mortality associated with bariatric surgery.
Given the paucity of effective and safe treatments for obesity, primary care has a major role to play in the prevention of this condition. That means starting intervention in childhood, where the obesity rate has soared from 6% to 19% since 1980. Since long-term obesity is highly refractory to treatment, prevention may be the best option—and that responsibility lies with primary care and with health policy, not with specialists.