What is obesity?

Maintaining a healthy body weight is one of the best ways to avoid weight-related health problems, such as type 2 diabetes or heart disease. But what exactly is a healthy body weight? A measurement based on your height and weight, called your body mass index or BMI, is considered to be a better measure of health risk than just your weight in pounds. In fact, the medical terms “overweight” and “obesity” are based on BMI values. A BMI between 25 and 30 is defined as overweight, and a BMI of 30 or more is considered obese. The higher your BMI, the greater your risk of developing a weight-related illness.

What is your BMI? Are you overweight or obese? You can find out by using the BMI Calculator or BMI Chart (PDF file: 1 page / 20 KB).

Funding and support for this material have been provided by VIVUS, Inc.

Risk Factors

Are there risk factors for obesity?

The main risk factor for obesity is overeating, or eating more calories than your body burns. Calories are the amount of energy in the food you eat. Some foods have more calories than others. For example, foods that are high in fat and sugar are also high in calories. If you eat more calories than your body uses, the extra calories will be stored as body fat. Other risk factors that contribute to obesity include:

  • Age
  • Being physically inactive
  • Genetics (obesity can run in families)
  • Poor sleeping habits
  • Pregnancy
  • Quitting smoking

There are some medical conditions and medicines that make it difficult to maintain a healthy body weight or to lose weight. If you think you have or have had any of the conditions or medicines listed below, be sure to talk to your doctor. In some cases, specific treatments for your medical condition or a change in medicines can make a difference in your efforts to manage your weight.

Some Medical Conditions That May Make It Difficult to Lose Weight

Hormonal disordersPolycystic ovary syndrome
Cushing’s disease
Cardiovascular disordersCongestive heart failure
Idiopathic hypertrophic cardiomyopathy
Heart valve disorders
Sleep disordersObstructive sleep apnea
Upper airway resistance syndrome
Eating disordersBulimia
Carbohydrate craving syndrome

Medicines That May Cause Weight Gain

  • Antihistamines, alpha blockers (allergies)
  • Beta blockers, methyldopa (high blood pressure)
  • Insulin, sulfonylureas (diabetes)
  • Lithium (manic-depressive illness)
  • Neuroleptics (schizophrenia)
  • Progestins (endometriosis)
  • Tricyclic antidepressants (depression)
  • Valproate (epilepsy)


How is obesity diagnosed?

If you think that you might be obese, or you are worried that you might be suffering from health issues related to your body weight, talk to your doctor. Your doctor will measure your height and your weight. He or she might also measure the circumference of your waist. With those measurements, your doctor will be able to tell you if you are overweight or obese, and what a healthy body weight would be for you.


What can I do to lose weight?

The first thing you should do is talk to your family doctor. Your doctor will help you develop a healthy eating and exercise plan that can help you lose weight, improve your fitness, and decrease the chances of developing heart disease, high blood pressure, or type 2 diabetes. Be sure to set realistic goals. Small changes can make a surprising difference in your health. Your doctor can offer practical suggestions that do not require a complete overhaul of your current way of life. In some cases, your physician may refer you to a nutrition specialist, such as a registered dietitian, for in-depth counseling about food choices.

Did You Know?

A pound of fat is about 3,500 calories. To lose 1 pound of fat in a week, you have to eat 3,500 fewer calories (about 500 fewer calories a day), or you have to “burn off” an extra 3,500 calories. You can burn off calories by exercising or just by being more active.

If you cut 250 calories from your diet each day and exercise enough to burn off 250 calories, that adds up to 500 fewer calories in one day. If you do this for 7 days, you can lose 1 pound of fat in a week.

In some cases, diet and exercise alone may not be enough to help you lose weight. Your doctor may talk to you about prescription weight-loss medicines. These medicines are only helpful when they are used in addition to healthy eating and exercise. Some of the prescription medicines your doctor may talk to you about include orlistat, lorcaserin, phentermine-topiramate (ER), and phentermine.

Your doctor may also talk to you about whether you might be a candidate for weight-loss surgery. Weight-loss surgery (bariatric surgery) can help you lose large amounts of weight if you are obese. Just like prescription medicines, weight-loss surgery is most successful when used as part of a long-term healthy lifestyle, including diet and exercise. Some of the more common weight-loss surgeries include:

  • Gastric bypass surgery. During this surgery, your doctor will make a small pouch at the top of your stomach. Your small intestine is then moved from the bottom of the stomach to the new pouch. When you eat, the food that you swallow goes into the new pouch and then into the small intestine, “bypassing” your stomach.
  • Laparoscopic adjustable gastric banding (also called the lap band). In this surgery, your doctor will place a band, like a belt, around your stomach, separating into two separate pouches. There is a small passage between the two pouches.
  • Bilipancreatic diversion with duodenal switch. During this surgery, your doctor will remove most of your stomach. Possible side effects include being unable to absorb all the vitamins and nutrients your body needs, so your doctor will closely monitor your progress after this surgery.
  • Gastric sleeve. In this surgery, part of your stomach is removed, creating less room for food.

If you are interested in weight-loss surgery, be sure to talk to your doctor. He or she can explain the different procedures, decide if you are a good candidate for surgery, and decide on a procedure that would be the best option for you.

Did You Know?

Many experts believe you should not try to lose more than 2 pounds per week. Losing more than 2 pounds in a week usually means that you are losing water weight and lean muscle mass instead of losing excess fat. If you do this, you will have less energy, and you will most likely gain the weight back.

What else can I do?

Losing weight is only half the battle. Keeping the weight off will require making permanent healthy changes to your lifestyle. A healthy diet that you can stick with, an exercise program that you enjoy, more daily activity, and the support of your friends, family, or outside group will be the keys to a successful weight-loss plan.

Getting Active

Lifestyle changes do not have to be drastic to be effective. Simple measures applied every day can make a significant difference over time. Some examples include:

  • Increasing your current physical activity by adding 10 minutes a day, or increasing the intensity from low to moderate. Limit time spent online, watching TV, and playing video games to less than two hours total per day.
  • Taking the stairs instead of the elevator
  • Parking at the far end of the parking lot and walking to your destination, rather than parking as close as possible. You can also get off the bus one stop earlier and walk the rest of the way.
  • Doing more household chores (such as dusting, vacuuming or weeding)
  • Walking or running with the dog and/or the kids
  • Taking “active” vacations—go hiking or ride bicycles
  • Buying a pedometer, which measures how many steps you take each day. Gradually increase your daily number of steps. (Pedometers can be purchased at sporting goods stores.)

Almost everyone can benefit from cutting back on unhealthy fat. If you currently eat a lot of fat, try just one or two of the following changes, or those suggested in our handout on healthier food choices:

  • Rather than frying meat, bake, grill or broil it. Take the skin off before eating chicken or turkey. Eat fish at least once a week.
  • Cut back on extra fat, such as butter or margarine on bread, sour cream on baked potatoes, and salad dressings. Use low-fat or nonfat versions of these condiments.
  • Eat plenty of fruits and vegetables both with your meals and as snacks.
  • When eating away from home, watch out for “hidden” fats (such as those in salad dressing and desserts) and larger portion sizes.
  • Read the nutrition labels on foods before you buy them. If you need help reading the labels, ask your doctor or your dietitian.
  • Drink no- or low-calorie beverages, such as water, unsweetened tea and diet soda. Sugar-sweetened drinks, such as fruit juice, fruit drinks, regular soft drinks, sports drinks, energy drinks, sweetened or flavored milk and sweetened iced tea can add lots of sugar and calories to your diet. But staying hydrated is important for good health.

Funding and support for this material have been provided by VIVUS, Inc.


What are the complications of obesity?

Obesity can contribute to a number of serious health problems, including:

  • Arthritis
  • Cancer
  • Coronary artery disease
  • Depression
  • Gallbladder disease
  • Gynecological problems, such as infertility
  • High blood pressure
  • High cholesterol
  • Metabolic syndrome
  • Stroke
  • Type 2 diabetes