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Obesity: Overview and Risk Factors

Obesity has become a worldwide epidemic. In the United States, more than 60 percent of the population is overweight or obese. Weight problems are typically classified based on body mass index (BMI), which is calculated by the following formula, in which weight is measured in kilograms and height is in meters:

BMI = weight

Use the BMI calculator to easily find your BMI by height and weight.

Overweight is defined as a BMI between 25 and 29.9 kg/m2, and obesity is defined as a BMI of 30 kg/m2 or greater.

Although genetic factors influence body weight, diet and lifestyle have a major effect as well. North Americans have long been heavier, compared with people in Asia or Africa where plant–based diets prevail, and vegetarians are typically slimmer than omnivores. The number of overweight and obese people in the United States increased by one–third between 1990 and 2000, due in part to larger portion sizes and increased availability of high–calorie foods, such as cheese and soft drinks.

Obesity is a strong risk factor for several chronic diseases, including high cholesterol, hypertension, heart disease, stroke, type 2 diabetes, gallstones, several types of cancer (particularly those arising in the breast, prostate, and colon), dementia, sleep apnea, infertility, and arthritis of the hips and knees.

Risk Factors

In addition to the contributions of diet and lifestyle, genetic factors play an important role. Dozens of genes coding for hormones, neurotransmitters, and receptors have been associated with body weight. Several are being investigated as a basis for possible pharmacologic therapies. These include leptin, ghrelin, and melanocortin. Depression, anxiety, and eating disorders may also contribute to disordered eating habits.

Obesity: Diagnosis and Treatment >>