How calories are used (energy metabolism). Some
people use calories efficiently—they need fewer calories to fuel the body,
which can result in "leftover" calories being stored as fat. Other people use
calories less efficiently—they need more calories to fuel the body, so there
are fewer leftover calories to store as fat.
Basal metabolic rate (BMR),
which is how much energy you burn when you are at rest. If you have a lower
BMR, it is easier to gain weight. Your BMR can change slightly in response to
certain conditions. For example, starvation or very low-calorie diets decrease
your BMR because you lose muscle as well as fat. Muscle increases your resting
metabolic rate, so losing too much muscle reduces metabolism. Fever and severe physical stress, such as recovery from
surgery or from extensive burns, increases your BMR.
signals. Hunger, fullness (satiety), and appetite are body signals that tell
you how much to eat. These signals also can be influenced by the environment
and can be ignored for short periods of time.
Hunger is a normal sensation (growling in
your stomach, feeling hunger pangs) that makes you want to eat. It is partially
controlled by a region of your brain called the
hypothalamus, your blood sugar (glucose) level, how
empty your stomach and intestines are, and certain hormone levels in your
Satiety is a feeling of fullness and satisfaction. Stretch
receptors in the stomach send signals to the brain that the stomach is filled.
Increased blood sugar (glucose), the activity of the hypothalamus, and the
presence of food in the intestines all contribute to
Appetite is a desire for or an interest in food that is
associated with the sight, smell, or thought of food. Appetite can override
hunger and satiety, such as when you continue to eat even after you feel full.
You can also have no appetite for food even though you are hungry, such as in a
stressful situation or during an illness.
Set point. This theory suggests that your body
tries to keep your weight within a specific range, called your set point. The
range seems to be influenced by your genetic makeup. But your actual weight
within that range is influenced by your lifestyle or environment. Your set
point adjusts to a new level when it is maintained over time and can be altered
by overeating, exercise, some medicines, and some brain conditions.
Fat distribution. Your weight distribution changes as you age.
Aging leads to replacement of lean muscle mass with fat. Men store more fat in
the abdomen as they age, while women store more in the hips and thighs. As women age, more fat is stored in the abdomen.
How this information was developed to help you make better health decisions.