Weight concerns Overweight and obesity

Case: M.B. is a 51-year-old female who presents asking for advice on how to lose weight. She is 160 cm tall and weighs 85 kg (body mass index, (BMI) = 33).

Table 3.4 Conditions in which weight loss is specifically recommended

To lower blood pressure in overweight and obese persons with high blood pressure To improve plasma lipid levels in overweight and obese persons with dislipidemia To lower blood glucose levels in overweight and obese persons with type 2 diabetes

She has been overweight all her life; everyone in her family is heavy. She has tried Weight Watchers, the Atkins diet, and several others diets. Sometimes she loses weight, but she always regains it. She wonders whether there's a way for her to really lose weight, or whether it's hopeless at this point in her life.

Obesity is one of the most important public health problems in the USA. The combined prevalence of overweight and obesity (defined as BMI greater than or equal to 25) in American adults is 59%.10 The prevalence of obesity (defined as BMI greater than or equal to 30) increased 61% between 1991 and 2000, to almost 20% of all USA adults.10

Strong evidence supports an association between obesity and increased morbidity and mortality. Recent research has linked excessive weight and body fat to a "dysmetabolic syndrome," which includes diabetes, hypertension, and coronary artery disease.11

Little evidence exists from prospective studies on the effect of weight loss by obese individuals on long-term morbidity and mortality. Nonetheless, in developing evidence-based guidelines for the treatment of obesity, a National Heart Lung and Blood Institute (NHLBI) expert panel assumed that, for most adults, the beneficial effects of weight loss exceed the potential risks.12 Weight loss is specifically recommended in the circumstances listed in Table 3.4 (all evidence level A).

The NHLBI guidelines recommend a two-step process of assessment and management. Treatment is recommended for patients with a BMI of25-29.9 or a high waist circumference, and two or more risk factors.10 Patients with a BMI of 30 or more should receive treatment regardless of risk factors. The initial goal for weight loss shouldbe to reduce body weight by 10% frombaseline (evidence level A). With success, further loss can be attempted, if warranted, based on further assessment. A combined intervention including caloric reduction, increased physical activity, and behavior therapy is recommended as most effective.

The key to weight control lies in the first concept of the normal healthy diet - balancing intake and output. In order to lose weight, one must burn off more calories than are taken in. If calories in (i.e. dietary intake) are fewer than calories out (energy expenditure through normal body maintenance and exercise), then the result will be weight loss. As long as the body's minimal requirements are met for protein, water, vitamins, and minerals, then reducing calories below maintenance level should allow for safe weight reduction.

This again raises the unbreakable link with activity levels: the less active a person is, the less they can eat without gaining weight. Physical activity is recommended as part of a comprehensive weight-control program because it contributes to weight loss (evidence level A), may decrease abdominal fat (evidence level B), increases cardiorespiratory fitness (evidence level A), and may help with maintenance of weight loss (evidence level C).10 Encouraging patients to be physically active and to become more fit (no matter what their weight) is more efficient than to tell them to exercise in order to lose weight.

The simplest approach to caloric reduction is reducing portion size. Caloric deficits are additive over time; decreasing intake by only 50 calories per day (the equivalent of half a cookie) will result in loss of 4.6 kg over a year. The NHLBI panel recommended a deficit of 500-1000 kcal/day to achieve a weight loss of 0.5-1 kg per week (evidence level A). Simply taking in a little less at each meal can make a significant impact over time. Combining this with an increase in activity amplifies the effect.

Reducing excessive dietary fat can also help. Fat has more than twice the number of calories per gram of either protein or carbohydrate. By replacing fatty foods with less fatty foods, the number of calories is decreased even without appreciably decreasing the portion size. For example, half a cup of potatoes with one teaspoon of butter or margarine has about 110 calories; without the added fat (butter or margarine), the potatoes have only 65 calories. Reducing dietary fat alone, without reducing total caloric intake, is not sufficient to create weight loss (evidence category A).10

There are many other approaches to weight loss that are promoted widely, many promising dramatic results in a short time. Some of the most well known are listed below:

• The Atkins Diet is a restricted-carbohydrate, high-protein, and restricted-fat diet. This diet takes advantage of the ketosis that develops during starvation; the resulting anorexia reduces appetite. However, ketosis can also cause fatigue, constipation, and vomiting. Potential long-term side effects include heart disease, bone loss, and kidney damage. In addition, high-protein, low-carbohydrate diets tend to be low in calcium, fiber, and healthy phyto-chemicals. The proponents of this diet advise taking vitamin and mineral supplements to replace lost nutrients.

• The Pritikin Diet is a very-low-fat (15% of calories), high-fiber, vegetarian (or nearly vegetarian) diet combined with exercise. It claims to reduce serum cholesterol and prevent or reverse cardiovascular disease.

• The Dean Ornish Diet carries low fat even further, with only 10% of calories being obtained from fat. Again, it claims reduction of serum cholesterol and prevention of heart disease.

• The Grapefruit Diet claims that grapefruit contains a special fat-burning enzyme that is activated when half a grapefruit is eaten for each meal along with small amounts of other food. As with all single-nutrient diets, excessive reliance on one food type leads to imbalance in nutrient intake, and deficiencies may develop over time. In addition, grapefruit has significant interactions with some prescription medications. None of these diets has any well-documented evidence supporting its use.

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