Obesity is an excess of body fat frequently resulting in a significant impairment of .
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 represent 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. .
Each fat cell weighs a very small amount (about 0.4 to 0.6 micrograms), the weight of these billions and billions of fat cells add up significantly. It's not very practical to count and measure the number of fat cells in a person's body, so science has come up with easier methods to determine if a person is obese.
Most common is a weight scale that you may have in your own bathroom but less common is BMI or Body Mass Index. This is the calculation to find yours. .
Weight (kg) .
height(m) x height(m).
What causes one person to gain weight while another person maintains their weight? .
As you grow older, your metabolic rate slows down and you do not require as many calories to maintain your weight. People frequently state that they eat the same and do the same activities as they did when they were 20 years old, but at 40, are gaining weight. Metabolism slows down, as you get older. Gender is also an important factor. Males have a higher resting metabolism than females, so males require more calories so they eat more. .
Amount of activity has a major affect on your weight. Active individuals require more calories than less active ones. Activity tends to diminish appetite in obese individuals while increasing the body's ability to preferentially metabolize fat as an energy source. Much of the increase in obesity in the last 20 years is felt to have resulted from the decreased level of physical activity in everyday life.