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Obesity: Overview and Risk Factors

Obesity has become a worldwide epidemic. In the United States, more than 60% of the population is overweight or obese. Weight conditions are typically classified based on body mass index (BMI), which is calculated by the following formula:

BMI = weight (kilograms)
height2 (meters)

Use the BMI calculator to find 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 major effect as well. 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, increased availability of high–calorie foods such as cheese and soft drinks, and decreased physical activity.

Obesity is a strong risk factor for several chronic diseases, including hyperlipidemia, cardiovascular disease, cerebrovascular disease, hypertension, type II diabetes, cholelithiasis, several types of cancer (particularly those arising in the breast, prostate, and colon), dementia, sleep apnea, pseudotumor cerebri, osteoarthritis of the hips and knees, and infertility.

Risk Factors

In addition to the contributions of increased energy intake and decreased physical activity to the risk of obesity, genetic factors play an important role. Dozens of genes coding for hormones, neurotransmitters, and receptors have been associated with weight control. Several mechanisms 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 habits that promote unhealthy weight gain.


Obesity: Diagnosis and Treatment >>