Women on the average have more body fat than men. The normal proportion of body fat to body weight is between 25 and 30 per cent in women versus 18 and 23 per cent in men. Women with over 30 per cent body fat and men with over 25 per cent body fat are considered obese.Causes of ObesityIn scientific terms, obesity occurs because a person's caloric intake from food exceeds the amount of energy he or she burns. The input surpasses the output leading to depositions of fat in the body. Though the exact causes of this imbalance between consuming and burning calories is unclear, there are some reasons that might be responsible for obesity.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, mounting evidence points to heredity as a strong determining factor for obesity.In one study of adults who were adopted as children, researchers found that the adult weights of the subjects were closer to the weights of their biological parents than their adoptive parents. The environment provided by the adoptive family apparently had less influence on the development of obesity than the person's genetic make-up.People can't change their genetic make-up, of course, but they can change what they eat and how active they are. Some people have been able to lose weight and keep it off by:Learning how to choose more nutritious meals that are lower in fat;Learning to recognise environmental cues (such as enticing smells or ads on television) that may make them want to eat when they are not hungry, and;Becoming more physically active.Environmental factors: People who feel that their genes have doomed them to a lifetime of obesity should take heart. Although genes are an important factor in many cases of obesity, a person's environment also plays a significant part. The environment includes lifestyle behaviours such as what and how often a person eats, and how active he or she is. Modern Indians tend to have high-fat diets, often putting taste and convenience ahead of nutritional value when choosing meals. In addition, most urban Indians don't get enough physical exercise.