Obesity

"Obesity" specifically refers to an excessive amount of body fat. "Overweight" refers to an excessive amount of body weight that includes muscle, bone, fat, and water. Today, more than 65 percent of adults in the United States are overweight or obese. Obesity puts people at increased risk for chronic diseases such as heart disease, type 2 diabetes, high blood pressure, stroke, and some forms of cancer.

Body Mass Index

The body mass index (BMI) is a tool used to assess overweight and obesity and monitor changes in body weight. It has limitations because it does not measure body fat or muscle directly. BMI is calculated by dividing a person's weight in pounds by height in inches squared and multiplied by 703.

Two people can have the same BMI but different body fat percentages. A bodybuilder with a large muscle mass and low percentage of body fat may have the same BMI as a person who has more body fat. However, a BMI of 30 or higher usually indicates excess body fat.

The BMI table provides a useful guideline to check your BMI. First, find your weight on the bottom of the graph. Go straight up from that point until you come to the line that matches your height. A BMI of 25 to 29.9 indicates a person is overweight. A person with a BMI of 30 or higher is considered obese.

Causes

Obesity occurs when a person consumes more calories from food than he or she burns. Our bodies need calories to sustain life and be physically active, but to maintain weight we need to balance the energy we eat with the energy we use. When a person eats more calories than he or she burns, the energy balance is tipped toward weight gain and obesity. This imbalance between calories-in and calories-out may differ from one person to another. Genetic, environmental, and other factors may all play a part. At the molecular level, a protein called leptin has been shown to play an important role in obesity (more info).

Treatment

Physical Activity

Physical activity helps you control your weight by using excess calories that would otherwise be stored as fat. Most foods you eat contain calories, and everything you do uses calories. Balancing the calories you eat with the calories you use through physical activity will help you reach and maintain a healthy weight. 

Experts recommend at least 30 minutes of moderate-intensity physical activity on most, if not all, days of the week. Physical activity may include structured activities such as walking, running, basketball, or other sports. It may also include daily activities such as household chores, yard work, or walking the dog. Pick a combination of structured and daily activities that fit your schedule.

Diet

For slightly overweight people (BMI 25-30), follow a healthy eating plan which:

• Emphasizes fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products.
• Includes lean meats, poultry, fish, bean, eggs, and nuts.
• Is low in saturated fats, trans fats, cholesterol, salt (sodium), and sugars.

For obese people with BMI greater than 30, a doctor may recommend very low-calorie diet (VLCD) that typically uses commercially prepared formulas to promote rapid weight loss. These formulas, usually liquid shakes or bars, replace all food intake for several weeks or months. VLCD formulas need to contain appropriate levels of vitamins and micronutrients to ensure that patients meet their nutritional requirements. Some physicians also prescribe very low-calorie diets made up almost entirely of lean protein foods, such as fish and chicken. People on a VLCD consume about 800 calories per day or less.

Medications

Appetite suppressants. They promote weight loss by decreasing appetite or increasing the feeling of being full. These medications make you feel less hungry by increasing one or more brain chemicals that affect mood and appetite. Phentermine and sibutramine are the most commonly prescribed appetite-suppressants in the U.S.

NOTE: Amphetamines are a type of appetite suppressant. However, amphetamines are not recommended for use in the treatment of obesity due to their strong potential for abuse and dependence.

Lipase inhibitors. They work by reducing the body’s ability to absorb dietary fat by about one third. It does this by blocking the enzyme lipase, which is responsible for breaking down dietary fat. When fat is not broken down, the body cannot absorb it, so fewer calories are taken in. Example: Orlistat. 

Surgery

Gastrointestinal surgery is an option for people who are severely obese and cannot lose weight by traditional means or who suffer from serious obesity-related health problems. The operation promotes weight loss by restricting food intake and, in some operations, interrupting the digestive process.

Gastrointestinal surgery for obesity, also called bariatric surgery, can be divided into three types: restrictive, malabsorptive, and combined restrictive/malabsorptive. Restrictive operations limit food intake by creating a narrow passage from the upper part of the stomach into the larger lower part, reducing the amount of food the stomach can hold and slowing the passage of food through the stomach. Malabsorptive operations do not limit food intake, but instead exclude most of the small intestine from the digestive tract so fewer calories and nutrients are absorbed. Malabsorptive operations, also called intestinal bypasses, are no longer recommended because they result in severe nutritional deficiencies. Combined operations use stomach restriction and a partial bypass of the small intestine.

Reference:

Weight-control Information Network