Genes and Family History
Studies of identical twins who have been raised apart show that genes have a strong influence on a person’s weight. Overweight and obesity tend to run in families. Your chances of being overweight are greater if one or both of your parents are overweight or obese.
Your genes also may affect the amount of fat you store in your body and where on your body you carry the extra fat. Because families also share food and physical activity habits, a link exists between genes and the environment.
Children adopt the habits of their parents. A child who has overweight parents who eat high-calorie foods and are inactive will likely become overweight too. However, if the family adopts healthy food and physical activity habits, the child’s chance of being overweight or obese is reduced.
Some hormone problems may cause overweight and obesity, such as underactive thyroid (hypothyroidism), Cushing’s syndrome, and polycystic ovarian syndrome (PCOS).
Underactive thyroid is a condition in which the thyroid gland doesn’t make enough thyroid hormone. Lack of thyroid hormone will slow down your metabolism and cause weight gain. You’ll also feel tired and weak.
Cushing’s syndrome is a condition in which the body’s adrenal glands make too much of the hormone cortisol. Cushing’s syndrome also can develop if a person takes high doses of certain medicines, such as prednisone, for long periods.
People who have Cushing’s syndrome gain weight, have upper-body obesity, a rounded face, fat around the neck, and thin arms and legs.
PCOS is a condition that affects about 5–10 percent of women of childbearing age. Women who have PCOS often are obese, have excess hair growth, and have reproductive problems and other health issues. These problems are caused by high levels of hormones called androgens.
Certain medicines may cause you to gain weight. These medicines include some corticosteroids, antidepressants, and seizure medicines.
These medicines can slow the rate at which your body burns calories, increase your appetite, or cause your body to hold on to extra water. All of these factors can lead to weight gain.
Some people eat more than usual when they’re bored, angry, or stressed. Over time, overeating will lead to weight gain and may cause overweight or obesity.