Obesity is complex. You gain weight when you take in more calories than you burn off. But other things can affect your weight. These things include:

What and how you eat.

Eating unhealthy foods and overeating are easy in our culture today. Many things influence eating behavior, including emotions, habits, and access to food.

How active you are.

Modern conveniences—such as elevators, cars, and the remote control for the television—cut activity out of our lives. Being active helps you stay fit. When you're fit, you burn more calories, even when you're resting.

Your genetic makeup.

Your genetic makeup has a very big effect on your weight. It affects:

• The rate at which your body uses energy (calories) when at rest, called your basal metabolic rate. Some people are born with higher basic metabolic rates than others. They naturally burn more calories than other people.
  • Regular physical activity can raise your metabolic rate.
  • Very low-calorie diets will lower your metabolic rate. A lower metabolic rate makes it easier to gain weight, because you don't burn calories as fast.
• Your body signals, such as your appetite and feeling hungry or full.
• Your fat distribution. You can't change where your body stores fat. Typically, men store fat in the belly (abdomen) while women store more in the hips and thighs. As women age, more fat is stored in the abdomen.

Medicines or health problems.

Some conditions and medicines may also cause weight gain. Examples include having Cushing's syndrome or hypothyroidism and taking certain antidepressants or corticosteroids.