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Obesity and Weight Loss Resource Center

Medically reviewed on Sep 26, 2016 by L. Anderson, PharmD

Maintaining a healthy weight is important to avoid life-threatening medical conditions and to prolong an active lifestyle. Obesity is a condition in which a person has an abnormally high and unhealthy proportion of body fat.

Staying at a healthy weight or losing weight requires a combination of regular exercise, healthy eating with portion and calorie control, and drinking low calorie fluids such as water.

A physician may decide that a weight loss medication may be an appropriate aid in some treatment plans. A patient and their physician may instead decide that surgical weight loss, such as gastric bypass surgery, is the appropriate action, based upon weight and current health risks.

Excess weight is a recognized risk factor for many health problems including:

Worldwide there are more than 500 million obese people, and in the U.S. alone, more than one-third of all adults suffer from obesity, being slightly higher in women. Obesity and is the second leading cause of preventable deaths in the U.S.

The terms “overweight” and “obese” have specific definitions in healthcare. Overweight and obese are both terms for a range of weight that are greater than what is considered healthy for a given height.1 For adults, overweight and obesity ranges are determined by using weight and height to calculate a number called the body mass index (BMI).3 BMI is used because it correlates with the amount of body fat. BMI is also important because the use of many weight loss drugs are based on a whether a person has reached a certain BMI.

  • An adult who has a BMI between 25 and 29.9 kg/m2 is considered overweight.
  • An adult who has a BMI of 30 kg/m2 or higher is considered obese.
  • An adult who is more than 100 pounds overweight or has a BMI over 40 kg/m2 is considered morbidly obese.

How to Determine Your Obesity Risk using BMI

Other factors besides BMI are considered in determining if someone is at risk for weight-related diseases. In addition to BMI, an individual's waist circumference and other disease or lifestyle attributes, such as high blood pressure, lack of exercise, or family history are predictors of obesity-related diseases.2

What Causes Weight Gain or Obesity?

  • Food intake, portion size and calorie content: Excessive food and calorie intake, more than the body needs for energy, can be turned into fat. Foods that are high in fat and sugar can contribute to obesity. If one does not burn more calories than they consume, they will put on weight.
  • Lifestyle: A sedentary lifestyle, without adequate exercise and proper nutrition, can lead to a higher risk of becoming overweight or obese. Incorporating exercise into a daily routine can help lower the risk of weight problems. Excessive food intake and a sedentary lifestyle ranks as one of the largest contributors to weight gain. Many smokers also gain weight when they quit smoking.
  • Genetics: Genetics may play a role in determining someone’s chances of being overweight or obese, but in general, many people still have the ability to control their weight. Only in rare genetic diseases is it impossible to avoid obesity. Weight history can also play a role - overweight children or adolescents are more likely to be overweight in adulthood.
  • Metabolic Rate: A metabolic rate, or metabolism, can differ among people with roughly the same height and weight. Someone with a low metabolic rate burns food more slowly than someone with a high metabolic rate. Someone with a low metabolic rate requires less calories to maintain a set weight than someone with a high metabolic rate.
  • Drugs: Certain drugs can lead to weight gain, including some antidepressants (Paxil (paroxetine), Zoloft (sertraline), Elavil (amitriptyline), and Remeron (mirtazapine). Steroids, including prednisone and methylprednisolone, and certain antipsychotic medications, such as Clozaril (clozapine), Zyprexa (olanzapine), Risperdal (risperidone) and Seroquel (quetiapine) are notorious for weight gain. Various epilepsy, diabetes, and blood pressure medications have also been linked to weight gain.
  • Pregnancy: Many women gain weight that remains after a pregnancy. A woman should not diet or use weight-loss medications when pregnant as it can be unsafe for the developing fetus. Women should consult with their obstetrician if they are concerned about weight gain in pregnancy.

Benefits to Weight Loss

Weight loss in individuals who are overweight or obese may reduce many health risks. Studies have found that weight loss with some medications can improve several health risks, such as:

  • high blood pressure, heart disease and stroke
  • high blood lipids (cholesterol, triglycerides)
  • diabetes and insulin resistance (the body’s inability to utilize blood sugar)
  • sleep apnea

Latest Weight Loss Drug Approvals

Anorexiants are the FDA-approved drugs that work in the brain to help suppress appetite and boost weight loss. Anorexiants are used as therapy for people who are overweight or obese with other risk factors, such as heart disease, high blood pressure, or diabetes. To view the latest weight loss drug approvals plus warnings, dosing, drug interactions, and side effects view the Anorexiant Drug Class.

Learn more about the latest weight-loss treatments with this slideshow.

  • In 2016, Belviq XR (lorcaserin) extended-release 20 mg, once-daily tablets were approved. Belviq is also available in a regular-release 10 mg twice daily formulation. Belviq is a serotonin 2C receptor agonist indicated for chronic weight management in adults who are obese or overweight based on body mass index (BMI) with at least one weight-related condition such as high blood pressure, type 2 diabetes, or high cholesterol.
  • In 2014, Saxenda (liraglutide) injection was approved for chronic weight management. Saxenda is for obese or overweight patients based on their BMI with at least one weight-related condition such as hypertension, type 2 diabetes, or high cholesterol. In one clinical trial, the average weight loss was 4.5 percent from baseline weight compared to treatment with a placebo (inactive pill) at one year.
  • Contrave (bupropion HCL/naltrexone HCL) was FDA-approved in 2014 for chronic weight management in addition to diet and physical activity. Contrave is an extended-release form of two previously approved drugs, naltrexone (ReVia, Vivitrol) and bupropion (Wellbutrin, Zyban). Contrave is used in obese or overweight adults with at least one weight-related condition such as high blood pressure or type 2 diabetes. In clinical trials, 36 to 48 percent of patients lost at least 5 percent of body weight compared to placebo.

See Also


  1. Centers for Disease Control and Prevention. Overweight and Obesity. Updated June 16, 2016. Accessed September 26, 2016 at
  2. Obesity. Accessed September 26, 2016 at
  3. Centers for Disease Control and Prevention (CDC). Assessing Your Weight: About Adult BMI. Updated May 15, 2015. Accessed September 16, 2016 at
  4. Department of Health and Human Services. NIH. National Heart, Lung and Blood Institute. Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults. Accessed September 26, 2016 at

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.