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Obesity is an excess of body fat that frequently results in a significant impairment of health. Obesity results when the size or number of fat cells in a person's body increases. A normal-sized person has between 30 and 35 billion fat cells. When a person gains weight, these fat cells first increase in size and later in number. One pound of body fat represents about 3500 calories.
When a person starts losing weight, the cells decrease in size, but the number of fat cells generally stays the same. This is part of the reason that once you gain a significant amount of weight, it is more difficult to lose it.
Causes:
Obesity results when there is an imbalance between energy intake and energy expenditure. In other words, you consume more calories than you expend in your daily activities. Weight gained during certain critical periods of your life more commonly lead to an increased number (as opposed to increased size) of fat cells and make obesity more difficult to treat.
Part of the food we eat is "burned" to make energy. We use this energy to move, breathe, and carry out all our normal daily activities. The amount of energy present in food is measured in calories. If a person takes in more calories than his or her body burns up, the extra calories are stored in the form of fat.
There are other reasons why an individual's body might retain fat. Some people have a larger appetite than others. Their bodies seem to expect them to eat more often. For others, their bodies do not efficiently convert food to energy. They are more likely to convert the food they eat to fat.
The major symptoms of obesity are excessive weight gain and the presence of large amounts of fatty tissue. Obesity can also give rise to several other conditions, including:
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