Tuesday, 17 July 2012

Prevention of Overweight Obesity

Overweight Obesity:

Obesity is now a true epidemic and public health crisis that both clinicians and patients must face. Normal body weight is defined as a body mass index (BMI), calculated as the weight in kilograms divided by the height in meters squared, of < 25 kg/m2; overweight is defined as a BMI = 25.0–29.9 kg/m2, and obesity as a BMI > 30 kg/m2. The prevalence of obesity in US children, adolescents, and adults has grown dramatically since 1990. In 2003–2004, 17% of US children and adolescents were overweight and 32% of adults were obese. Among men, the prevalence of obesity increased significantly between 1999 and 2000 (28%) and between 2003 and 2004 (31%). Among women, no significant increase in the prevalence of obesity was observed between 1999 and 2000 (33%) or between 2003 and 2004 (33%). The prevalence of extreme obesity (BMI  40) in 2003–2004 was 3% in men and 7% in women. Prevalence varies by race and age, with older African American and Latina women having the greatest prevalence of obesity. This trend has been linked both to declines in physical activity and to increased caloric intake in diets rich in fats and carbohydrates.

Adequate levels of physical activity appear to be important for the prevention of weight gain and the development of obesity. However, as noted above, only about 20% of Americans are physically active at a moderate level, and only 8% at a more vigorous level, and 60% report irregular or no leisure time physical activity. In addition, only 3% of Americans meet four of the five recommendations for the intake of grains, fruits, vegetables, dairy products, and meat of the Food Guide Pyramid. Only one of four Americans eats the recommended five or more fruits and vegetables per day.

Risk assessment of the overweight and obese patient begins with determination of BMI, waist circumference for those with a BMI of 35 or less, presence of comorbid conditions, and a fasting blood glucose and lipid panel. Obesity is clearly associated with type 2 diabetes mellitus, hypertension, hyperlipidemia, cancer, osteoarthritis, cardiovascular disease, obstructive sleep apnea, and asthma. One of the most important sequelae of the rapid surge in prevalence of overweight and obesity between 1990 and 2000 has been a dramatic 30–40% increase in the prevalence of type 2 diabetes mellitus. In addition, almost one-quarter of the US population currently has the metabolic syndrome, putting them at high risk for the development of CHD. The relationship between overweight and obesity and diabetes, hypertension, and coronary artery disease is thought to be due to insulin resistance and compensatory hyperinsulinemia. Persons with a BMI  40 have death rates from cancers that are 52% higher for men and 62% higher for women than the rates in men and women of normal weight. Significant trends of increasing risk of death with higher BMIs are observed for cancers of the stomach and prostate in men and for cancers of the breast, uterus, cervix, and ovary in women, and for cancers of the esophagus, colon and rectum, liver, gallbladder, pancreas, and kidney, non-Hodgkin lymphoma, and multiple myeloma in both men and women.

In the Framingham Heart Study, overweight and obesity were associated with large decreases in life expectancy. For example, 40-year-old female nonsmokers lost 3.3 years and 40-year-old male nonsmokers lost 3.1 years of life expectancy because of overweight, and 7.1 years and 5.8 years of life expectancy, respectively, because of obesity. Obese female smokers lost 7.2 years and obese male smokers lost 6.7 years of life expectancy compared with normal-weight smokers, and 13.3 years and 13.7 years, respectively, compared with normal-weight nonsmokers. Clinicians must work to identify and provide the best prevention and treatment strategies for patients who are overweight and obese. Patients with abdominal obesity (high waist to hip size ratio) are at particularly increased risk. Control of visceral obesity in addition to other cardiovascular risk factors (hypertension, insulin resistance, and dyslipidemia) is essential to reducing cardiovascular risk.

CURRENT Practice Guidelines in Primary Care :

Prevention of overweight and obesity involves both increasing physical activity and dietary modification to reduce caloric intake. Clinicians can help guide patients to develop personalized eating plans to reduce energy intake, particularly by recognizing the contributions of fat, concentrated carbohydrates, and large portion sizes (see Chapter 29: Nutritional Disorders). Patients typically underestimate caloric content, especially when consuming food away from home. Providing patients with caloric and nutritional information may help address the current obesity epidemic. To prevent the long-term chronic disease sequelae of overweight or obesity, clinicians must work with patients to modify other risk factors, eg, by smoking cessation (see above) and strict glycemic and blood pressure control (see Chapter 27: Diabetes Mellitus & Hypoglycemia and Systemic Hypertension).

Lifestyle modification, including diet, physical activity, and behavior therapy, has been shown to induce clinically significant weight loss. Other treatment options for obesity include pharmacotherapy and surgery. One potentially effective diet strategy is the replacement of caloric beverages with low-calorie or noncaloric beverages. As noted above, in overweight and obese persons, at least 60 minutes of moderate-high intensity physical activity may be necessary to maximize weight loss and prevent significant weight regain. Counseling interventions or pharmacotherapy can produce modest (3–5 kg) sustained weight loss over 6–12 months. Pharmacotherapy appears safe in the short term; long-term safety is still not established. As an example, in a multicenter trial, treatment with 20 mg/d of rimonabant, a selective cannabinoid-1 receptor blocker, plus diet for 2 years produced modest but sustained reductions in weight and waist circumference and favorable changes in metabolic risk factors. Counseling appears to be most effective when intensive and combined with behavioral therapy. Maintenance strategies can help preserve weight loss.

In dietary therapy, results from the Women's Health Initiative Dietary Modification Trial showed that a low-fat diet high in vegetables, fruits, and grains produced a modest (2.2 kg, P < .001) weight loss that was sustained over prolonged follow-up (1.9 kg, P < .001 at 1 year, 0.4 kg, P = .01 at 7.5 years). A recent study comparing various diets revealed that Mediterranean (moderate fat, restricted calorie) and low-carbohydrate (non-restricted calorie) diets are effective alternatives to low-fat diets.

Weight loss strategies using dietary, physical activity, or behavioral interventions can produce significant improvements in weight among persons with prediabetes and a significant decrease in diabetes incidence. Multicomponent interventions including very-low-calorie or low-calorie diets hold promise for achieving weight loss in adults with type 2 diabetes mellitus.

Bariatric surgical procedures, eg, vertical banded gastroplasty and Roux-en-Y gastric bypass, are reserved for patients with morbid obesity whose BMI exceeds 40, or for less severely obese patients (with BMIs between 35 and 40) with high-risk comorbid conditions such as life-threatening cardiopulmonary problems (eg, severe sleep apnea, pickwickian syndrome, and obesity-related cardiomyopathy) or severe diabetes mellitus. In selected patients, surgery can produce substantial weight loss (10 to 159 kg) over 1 to 5 years, with rare but sometimes severe complications. Nutritional deficiencies are one complication of bariatric surgical procedures and close monitoring of a patient's metabolic and nutritional status is essential.

Clinicians seem to share a general perception that almost no one succeeds in long-term maintenance of weight loss. However, research demonstrates that approximately 20% of overweight individuals are successful at long-term weight loss (defined as losing 10% of initial body weight and maintaining the loss for 1 year). National Weight Control Registry members who lost an average of 33 kg and maintained the loss for more than 5 years have provided useful information about how to maintain weight loss. Members report engaging in high levels of physical activity (approximately 60 min/d), eating a low-calorie, low-fat diet, eating breakfast regularly, self-monitoring weight, and maintaining a consistent eating pattern from weekdays to weekends. The development and implementation of innovative public health strategies is essential in the fight against obesity. Lessons learned from smoking cessation campaigns may be helpful in the battle against this significant public health concern.

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