What is the body mass index?

The body mass index (BMI) is a tool that often is used to measure body fat. It is based on height and weight. To find out your BMI, you can use the online calculator at www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm.

What BMI range is considered a normal weight?

A person with a BMI of 18.5–24.9 is a normal weight.

What BMI range is considered overweight?

A person with a BMI of 25–29.9 is overweight.

What BMI range is considered obese?

A person with a BMI of 30 or higher is obese. About one third of women in the United States are obese.

What are calories?

Energy is measured in calories. Calories also measure how much fuel is in a certain food.

How does calorie intake affect my weight?

The body uses only as many calories as it needs for energy. Any calories that are left over are stored as fat in the body. Taking in more calories than you use up is the most important factor that leads to weight gain.

Click on the FAQs below to expand

What other factors affect weight besides excess calories?

Some other factors that affect weight control include the following:

  • Age—It is normal to gain a little weight as you grow older.
  • Genes—Genes may affect a person’s weight directly or indirectly. Some people have genetic disorders that lead to obesity.
  • Pregnancy—After having a baby, a woman might not lose all of the weight she gained during pregnancy. If this happens with each pregnancy, the weight can add up.

What health problems are associated with being overweight?

Many serious health problems are linked to being overweight or obese:

  • Cardiovascular disease
  • Diabetes
  • Gallbladder disease
  • Certain types of cancer, such as cancer of the endometrium, breast, colon, and gallbladder; obesity also may increase the risk of ovarian cancer.
  • Sleep apnea
  • Joint disease
  • Infertility

How does excess weight affect pregnancy?

Women who are overweight or obese have a higher risk of developing diabetes and high blood pressure during pregnancy than women of normal weight. Overweight or obese women also are more likely to have a cesarean delivery.

How can I lose weight?

To lose weight, you need to use up more calories than you take in. You can do this by getting regular exercise combined with a program of healthy eating.

What resources are available to help me lose weight?

The U.S. Department of Agriculture’s web site “MyPlate” (www.choosemyplate.gov) can help you plan a balanced diet. It offers a diet-tracking program called “SuperTracker” that takes into account your age, sex, height, weight, and physical activity.

What foods should I limit if I am trying to lose weight?

Eat fewer foods that are high in sugar and fat. An easy way to cut calories and to reduce the amount of sugar you eat is to avoid sugary drinks, such as soft drinks and sweetened tea.

What other eating habits can help me lose weight?

Portion control is key. Eat smaller amounts of all foods. For example, a 3-ounce serving of meat or poultry is the size of a deck of cards. A tablespoon of butter is about the size of a poker chip.

How much exercise do I need to lose weight and keep it off?

People who have lost weight and kept it off generally get 60–90 minutes of moderate intensity activity on most days of the week. You do not have to do this all at once. For instance, you can exercise for 20–30 minutes three times a day.

Does exercise have additional benefits other than helping with weight loss and maintaining a healthy weight?

Exercise promotes general health and increases mental well-being. Your endurance increases, as does your flexibility and muscle strength. Exercise can help reduce symptoms of depression and anxiety in some people. Your risk of heart disease, colon cancer, and diabetes decreases with regular physical activity.

I have tried to lose weight with diet and exercise, but I am still overweight. Can medication help me lose weight?

For some people, it may be hard to lose weight through diet and exercise alone. If you have a BMI greater than 30, or a BMI of at least 27 with certain medical conditions, such as diabetes or heart disease, medications may be able to help you lose weight.

When is surgery an appropriate option to help with weight loss?

If diet and exercise do not work, a special type of surgery, bariatric surgery, may be an option for people who are very obese (a BMI of 40 or greater) or who have a BMI between 35 and 39 and also have major health problems caused by obesity. Bariatric surgery can result in significant weight loss. This may decrease the risk of the serious health problems associated with obesity.

What are the risks associated with bariatric surgery?

The risks of bariatric surgery may include the following:

  • Leaking of stomach juices into the abdomen
  • Injury to other organs, such as the spleen
  • Wearing away of the band or staples used in the surgery
  • Infection
  • Complications from anesthesia
  • Death

What effects are associated with bariatric surgery other than weight loss?

This surgery may have long-term effects on your body, such as changes in bowel habits and eating patterns. You may need to take vitamin and mineral supplements, such as vitamin B12 and iron, for the rest of your life.

How long do I need to wait after having bariatric surgery to become pregnant?

You should delay getting pregnant for 12–24 months after having bariatric surgery, when you will have the most rapid weight loss.


Anesthesia: Relief of pain by loss of sensation.

Bariatric Surgery: Surgical procedures that cause weight loss for the treatment of obesity.

Body Mass Index (BMI): A number calculated from height and weight that is used to determine whether a person is underweight, normal weight, overweight, or obese.

Calories: Units of heat used to express the fuel or energy value of food.

Cardiovascular Disease: Disease of the heart and blood vessels.

Cesarean Delivery: Delivery of a baby through surgical incisions made in the mother’s abdomen and uterus.

Diabetes: A condition in which the levels of sugar in the blood are too high.

Endometrium: The lining of the uterus.

Genes: Segments of DNA that contain instructions for the development of a person’s physical traits and control of the processes in the body. They are the basic units of heredity and can be passed down from parent to offspring.

Infertility: A condition in which a couple has been unable to get pregnant after 12 months without the use of any form of birth control.

Sleep Apnea: A disorder characterized by interruptions of breathing during sleep that can lead to other health problems.

If you have further questions, contact your obstetrician–gynecologist.

Designed as an aid to patients, this document sets forth current information and opinions related to women’s health. The information does not dictate an exclusive course of treatment or procedure to be followed and should not be construed as excluding other acceptable methods of practice. Variations, taking into account the needs of the individual patient, resources, and limitations unique to the institution or type of practice, may be appropriate.