- Body mass index (BMI): If your BMI is 30 or greater, you're considered obese and should talk to your doctor about losing weight for your health.
- Waist circumference: If you have an "apple shape" — a "potbelly" or "spare tire" — you carry more fat in and around your abdominal organs. Fat in your abdomen increases your risk of many of the serious conditions associated with obesity. Women's waist measurement should fall below 35 inches. Men's should be less than 40 inches. If you have a large waist circumference, talk to your doctor about weight loss.
In scientific terms, obesity occurs when a person's calorie intake exceeds the amount of energy he or she burns. What causes this imbalance between consuming and burning calories is unclear. Evidence suggests that obesity often has more than one cause. Environmental, psychological, genetic, and other factors all may play a part.
Environmental factors: A person's environment plays a significant role in weight status. The Environment includes lifestyle behaviors, such as what a person eats and how active he or she is. Americans tend to have high-fat diets, often putting taste and convenience ahead of nutritional content when choosing meals.
Psychological factors: Psychological factors also may influence eating habits. Many people eat in response to negative emotions such as boredom, sadness, or anger.
About 30% of those who seek treatment for serious weight problems have difficulties with binge eating. During a binge eating episode, people eat large amounts of food while feeling they can't control how much they are eating. Those with the most severe binge eating problems are considered to have what is called binge eating disorder. These people may have more difficulty losing weight and keeping the weight off than people without binge eating problems. Some will need special help, such as counseling or medication, to control their binge eating before they can successfully manage their weight.
Genetic factors: Obesity tends to run in families, suggesting that it may have a genetic cause. However, family members share not only genes but also diet and lifestyle habits that may contribute to obesity. Separating these lifestyle factors from genetic ones is often difficult. Still, growing evidence points to heredity as a strong determining factor of obesity. However, many people genetically predisposed to obesity do not become obese or are able to lose weight and keep it off.
Other causes of obesity: Some illnesses can lower the metabolism or trigger an increased appetite which can cause obesity. These include hypothyroidism, Cushing's syndrome, depression, and certain neurologic problems. Certain drugs, such as steroids and some antidepressants, may cause excessive weight gain through the same methods. A doctor can determine if a patient has any of these conditions, which are believed to be responsible for only about 1% of all cases of obesity.
- Heart disease and stroke
- High blood pressure
- Gallbladder disease and gallstones
- Breathing problems, such as sleep apnea (when a person stops breathing for a short time during sleep) and asthma
- The Family history of certain chronic diseases: People with close relatives who have had heart disease or diabetes are more likely to develop these problems if they are obese.
- Pre-existing medical conditions: High blood pressure, high cholesterol levels, or high blood sugar levels are all warning signs of some obesity-associated diseases.
- "Apple" shape: People whose weight is concentrated around the abdomen may be at greater risk of developing heart disease, diabetes, or cancer than people of the same weight who are "pear-shaped."