Obesity

September 20, 2011

Obesity is a rapidly growing problem in the United States today, reaching epidemic proportions. According to the Centers for Disease Control and Prevention, during 1999-2000, 64% of Americans were overweight or obese, with 23% actually defined as being obese (see definitions below). Thirty percent of children and adolescents during the same time period were found to be overweight. The prevalence of obesity has escalated over the years: between 1971 and 1974, only 24.7% of the adult population was affected. Obesity is more common in women, affecting 34.8 million women compared with 26.4 million men. Obesity affects all socioeconomic and ethnic groups, particularly the less privileged and minorities. Nationally, this problem needs to be addressed promptly because obesity leads to multiple medical problems that substantially affect the quality of life, longevity, and health care costs.

DEFINITION

Overweight refers to increased weight for given height. Obesity refers to excessive amounts of body fat relative to lean body mass. Weight is proportionate to height and is adjusted using the body mass index (BMI). Body mass index is calculated as a ratio of an individual’s weight in kilograms, divided by the square of height measured in meters. A Body mass index greater than 30 defines obesity (Table 1).

Table 1. Classification of overweight and obesity
Body mass index (kg/m2)
Underweight < 18.5
Normal 18.5-24.9
Overweight 25.0-29.9
Obese
Class I 30-34.9
Class II 35.0-39.9
Class III a 40 (extreme obesity)

Other measures of obesity include measurement of the waist circumference. Waist circumference greater than 88 cm (35 in.) in women or greater than 102 cm (40 in.) in men indicates increased abdominal fat, which is associated with insulin resistance, high cholesterol, and coronary artery disease. Obesity can be described as android (abdominal fat accumulation, or “appleshaped”) or gynecoid (mostly peripheral fat distribution, favoring the hips and lower extremities, or “pear-shaped”).

CAUSES OF OBESITY

Why is obesity such a growing problem? Nationally, the main problem appears to be that calorie-dense foods are easily available, which increases caloric intake, along with lifestyle changes, including reduced physical activity. There are complex interactions between hormones that control feeding, fat breakdown, and fat storage. These include insulin, leptin, neuropeptide Y, and others. There are also rare genetic syndromes that affect a small minority of people. The number of overweight and obese children has been rising, which contributes to the growing pool of obese adults.

COMPLICATIONS OF OBESITY

Obesity leads to complications that involve many organ systems (Table 2). Obesity is a leading cause of type 2 diabetes. In android (apple-shaped) obesity, fat is deposited in the abdomen in the form of triglycerides, or storage fat. Triglycerides in the abdomen are broken down into free fatty acids, which oppose the action of insulin and prevent tissues and organs from using glucose in the blood. High blood sugars result, and this eventually progresses to diabetes. Problems with insulin secretion may also occur as a result of this process. Triglyceride deposits also provide a source of fatty acids for lipid and cholesterol production, leading to clogged arteries. Blocked arteries can lead to heart attacks, strokes, kidney failure, impotence, abdominal pain, leg pain, and even gangrene.

Table 2. Complications of obesity
Cardiovascular

  • High blood pressure
  • Heart failure
  • Angina, heart attack
  • Stroke
  • Blood clots in leg veins and lungs
  • Lower leg swelling
Respiratory

  • Sleep apnea
  • Restrictive lung disease
Female reproductive and urinary problems

  • Irregular menstrual cycles
  • Infertility
  • Increased risk of cancer of the breast, uterus, colon
  • Urinary incontinence
Infectious

  • Superficial fungal skin-fold infections
  • Leg ulcers
Gastrointestinal

  • Gallstones, inflamed gallbladder
Metabolic

  • High cholesterol, high triglycerides
  • Diabetes
  • High uric acid, causing gout and kidney stones
Musculoskeletal

  • Low back pain
  • Degenerative arthritis, particularly knees and spine
Psychological/social

  • Depression
  • Social isolation
  • Impaired activities of daily living
  • Limited physical activity choices

Restrictive lung disease can result if obesity interferes with the ability to deeply inhale and adequately exhale, resulting in low blood oxygen levels and occasionally high carbon dioxide levels. Such patients may require long-term, low-dose oxygen therapy. Sleep apnea due to excess amounts of tissue in the neck can lead to loud snoring and blockage of airway at the level of the pharynx. This leads to a drop in oxygen levels, which produces strain on the right side of the heart, resulting in heart failure and widespread swelling (edema). Sleep apnea with loud snoring has been known to result in marital discord as well. Finally, sleep apnea is associated with abnormal heart rhythms and high blood pressure.

Obese persons who are sedentary are at risk of forming clots in the deep veins of their legs. Clots in the veins can occasionally fragment and travel upward to the heart and lungs, which can be fatal.

Women with obesity are prone to developing menstrual irregularities. Abdominal fat deposition leads to insulin resistance, which can lead to hormonal imbalances in the ovary, which prevent ovulation. Infertility may result and some women may need assistance with ovulation and expert fertility evaluation. Also, higher levels of testosterone and other ovarian hormones can lead to acne and excess facial, abdominal, and chest hair. This is a difficult cosmetic problem and is a source of low self-esteem. Missed menstrual cycles can lead to an abnormal buildup of the inner lining of the uterus (endometrium), which can lead to uterine cancer. Finally, obesity is associated with an increased risk of breast cancer.

Low back and knee pain are frequent consequences of excess weight. Joint degeneration occurs faster in obese individuals. Joint replacement surgery is often difficult in these patients. Chronic pain often occurs even in spite of surgery. Many individuals require canes, walkers, wheelchairs, or motorized vehicles to assist with mobility for activities of daily living.

Superficial skin fungus infections may occur beneath the breasts, in the neck folds, armpits, and groin as a result of moisture from sweating between adjacent folds of skin. These can be a chronic problem and may predispose to bacterial infection, as well as causing social embarrassment.

Many obese patients are depressed. It can be difficult to tell whether depression causes altered feeding behavior leading to obesity, or whether obesity leads to depression. In some patients, a vicious cycle of obesity and depression may occur. Body-image consciousness in society leads to great difficulties for obese persons, who are often viewed in a negative light by their nonobese peers. This may lead to social isolation, difficulties obtaining employment, and in forming meaningful relationships.

TREATMENT  OF OBESITY

Obesity is typically a chronic disease that is difficult to treat and requires ongoing management. Many patients will require lifelong attention to control weight with diet and regular exercise. Patients need to be informed that obesity-related illness and death can be significantly reduced with a weight loss of only 5-10% of their body weight. The physician and patient need to openly discuss realistic weight loss goals and assess the patient’s readiness to participate in a weight loss program. Gradual changes should be encouraged, potential adverse outcomes discussed, and ongoing positive reinforcement provided.

DIET

There are a variety of recommended diets to promote weight loss. Regardless of the type of diet, a net reduction in caloric intake is required to lose weight. Popular low-carbohydrate diets go against this rule (not really as even they produce a net caloric deficit, but with a skewed nutrient intake) but need further study to see if they are safe and effective in the long term. Obese patients on low-calorie diets (LCD) of 1,000-1,500 kCal per day can lose about 8% of their weight. Very low-calorie diets (VLCD) of 400-800 kCal per day understandably lead to greater weight loss, up to 13-23 kg. However, this weight loss is hard to maintain. Evidence shows that at the end of 1 year, those who followed either a VLCD or a LCD approached similar weights. VLCD should therefore be recommended only if immediate weight loss is required for health reasons or surgery. Patients should be encouraged to eat a variety of nutrient-rich foods incorporating fruits, vegetables, fiber, and vitamins. Carbohydrates should be derived from whole foods; processed foods should be avoided. Low-fat diets can be effective in cutting back calories.

The primary care provider should evaluate the obese patient for obesity-related diseases. Consultation with a nutritionist is essential to calculate caloric needs according to the estimated ideal body weight and level of physical activity. Special diets may be needed for the patient with diabetes, high blood pressure, cholesterol or triglyceride disorders, kidney stones, and heart failure.

EXERCISE

Thirty-eight percent of adult Americans reported no leisure-time physical activity in 1997-1998. Physical inactivity increases the risk for heart disease and for high blood pressure. Women were found to be less physically active than men. More African Americans and Hispanics than whites were found to be sedentary, as were the elderly and the less affluent. Girls with a higher BMI exercised even less. Introducing physical activity in an obese patient should be a gradual process and slowly increased as tolerated. Regular aerobic exercise (brisk walking, aerobic dancing, jogging/running, swimming, exercise bike) will produce modest weight loss in overweight and obese adults, even without dietary calorie reduction. Finally, a combination of LCD and exercise produces more weight reduction than either one alone.

BEHAVIOR THERAPY

Behavior modification is important in achieving successful weight loss. This can be done either with a therapist (individually or in a group) or with a physician. Weight loss of about 10% of body weight can be expected with behavior modification alone. Attention to self-monitoring of eating behavior is important, by keeping a food diary of calories, portion sizes, emotions leading to eating, and location of eating. A similar exercise log is also useful. Patients need to work on controlling their impulses when shopping for food or making menu selections. Positive changes lead to reinforcement, such as monitoring weight loss. Involvement in a support group may avoid relapses.

MEDICATION

Medications are not routinely recommended because of side effects, limited effectiveness, and the need for more healthful interventions in the form of diet and exercise. Medications are recommended only in patients with a Body mass index > 30 who do not have obesity-associated risk factors or diseases, or in those with a Body mass index > 27 who do have obesity-related risk factors or diseases. Medication should be used along with, rather than as a substitute for, diet and exercise. The two medications that are currently approved for long-term treatment of obesity are orlistat and sibutramine. Orlistat inhibits 30% of fat absorption from the intestines and can also lower cholesterol somewhat. In studies, orlistat produces a 5-10% reduction in body fat. side effects are excess gas, abdominal pain, oily rectal spotting, and incontinence of stool. The symptoms improve with time and fiber may help. Fat-soluble vitamins can be lost in the stool and supplements are recommended.

Sibutramine acts in the brain by suppressing reuptake of the transmitters norepinephrine and serotonin. This reduces appetite and therefore caloric intake. Patients may lose 5% or more of their body weight with this medication. Blood pressure elevation can occur and needs to be monitored closely. Other side effects, including dry mouth, insomnia, headache, and constipation, are mild and diminish with time.

SURGERY

Bariatric surgery is the most effective treatment for severe obesity. Bariatric surgery can be considered in patients who are 18 years or older with BMI > 40, or BMI between 35 and 40 if there are major weightrelated complications. Patients must have failed nonsurgical methods of weight loss and/or failed treatment in obesity clinics and must be committed to long-term follow-up. They must not have medical or psychological conditions that prevent the use of anesthesia or surgery. The goal of bariatric surgery is to reduce the size of the stomach (as in vertical banded gastroplasty) or to create malabsorption of nutrients (as with the Roux-en-Y gastric bypass).

Vertical banded gastroplasty (“stomach stapling”) allows for weight loss of 20% of body weight during up to 5 years of follow-up. However, weight gain can occur in patients who consume high-calorie foods in the form of soft foods or liquids (ice cream or sugary drinks). Gastric bypass is the most effective surgery for extreme obesity, but leads to diversion of the stomach into the small intestine, and results in malabsorption of nutrients. Weight loss after gastric bypass ranges from 50 kg to as much as 100 kg, but this procedure carries a higher risk of complications and patients need to be followed closely for nutrient supplementation.

SEE ALSO: Body mass index, Diabetes, Nutrition, Weight control

Suggested Reading

  • Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion. Overweight and obesity.
  • Nambi, V., Hoogwerf, R., & Sprecher, D. (2002). A truly deadly quartet: Obesity, hypertension, hypertriglyceridemia, and hyperinsulinemia. Cleveland Clinic Journal of Medicine, 69, 985-989.
  • NHLBI Obesity Education Initiative Expert Panel on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. (1998).
  • Prystowsky, J. (2002). Surgical management of obesity. Seminars in Gastrointestinal Disease, 13, 133-142.
  • Yanovski S. Z., & Yanovski J. A. (2002). Drug therapy: Obesity. New England Journal of Medicine, 346, 591-602.

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