Obesity and overweight

Any unneeded energy in food, whether it comes from carbohydrates, proteins, or lipids, is stored in the body as fat. An extra 3,900 kilocalories of energy results in the storage of 0.5 kg of fat. People who consistently consume more food energy then they need gain weight. People who continue to store fat and gain weight may eventually become obese.
Obesity occurs when the body mass index is 30.0 kg/m2 or greater. Body mass index (BMI) or Quetelet index is a simple way to estimate the percentage of fat in the body. It is calculated by dividing an individual’s weight (in kilograms) by the square of the individual’s height (in meters). For example, a man who weighs 88 kilograms and is 1.7 meters tall has a BMI of:
88 kg ÷ (1.7 m)2 = 30.4 kg/m2.
Compare this BMI with the BMI values in Table below. The man’s BMI is greater than 29.9 kg/m2, so he would be considered obese.

Weight Status	BMI Value (kg/m2)
Underweight	less than 18.4
Normal	from 18.5 to 24.9
Overweight	from 25 to 29.9
Obese	more than 30

People who are obese are at greater risk of many serious health problems, they have a cluster of conditions that together greatly increase the risk of cardiovascular disease. The conditions include type 2 diabetes, high blood pressure, and high blood levels of cholesterol and triglycerides. In addition, people who are obese have a lower life expectancy. Obesity is now a leading public health problem in many countries.
The combination of eating too much and moving too little generally causes obesity. The best way to lose weight and avoid obesity is to eat less and exercise more. However, many factors may play a role in obesity. Several genes have been identified that control appetite and may contribute to some cases of obesity. Also are important the environmental factors such as the availability of high-fat, high-Calorie fast foods and food advertisements.