Prescription Weight Loss Drugs 101

Posted: December 1, 2020 in Obesity Medicine by

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In addition to diet and exercise, your weight loss doctor may prescribe certain types of medications to help you lose weight. Learn more about the types of prescription weight loss medications available, how they work, and who should consider taking them.

What are the Types of Prescription Weight Loss Medications?

Most prescription weight loss drugs fall into one of three categories: appetite suppressants, intestinal peptides, or fat absorption inhibitors.

  • Appetite suppressants are the most common type of weight-loss medications prescribed. They fall into two classes: stimulants that also raise metabolism, and non-stimulants. They usually come in the form of tablets or extended-release capsules, which release medication into the bloodstream. Appetite suppressants act on the hypothalamus-the appetite center. Often this is done by increasing serotonin, dopamine, or catecholamine – chemicals that affect mood and appetite. The goal of appetite suppressants is to help you lose weight by eating less.  The stimulant class reduces intake and also raises the number of calories your body burns each day. 
  • Intestinal Peptides are natural body proteins that are modified to last longer in the body. Most are given by a very tiny needle, and at least one is a tablet. They reduce the emptying of the stomach and cause a feeling of fullness. They also normalize blood sugars. 
  • Fat absorption inhibitors, on the other hand, work by preventing your body from breaking down and absorbing the fact that you do eat. This unabsorbed fat is then eliminated through bowel movements. Xenical is the only fat absorption inhibitor approved for use in the United States, and it is available over the counter as Alli. While Xenical blocks the absorption of fat in the body, it also reduces the absorption of some vitamins. People who take fat absorption inhibitors may need to take additional supplements to make up for this reduced vitamin absorption.

Who Should Take Prescription Weight Loss Medications?

Weight-loss medications are considered to be moderately effective, generating a weight loss of 5 to 22 pounds in a year; and are much more effective when part of a comprehensive medical weight loss program. In these cases, losses of 15-20% are more common. In general, prescription weight loss medications are reserved for people with a body mass index of 30 and above with no obesity-related conditions, people with a BMI of 27 and above with obesity-related health problems, or those with an elevated body fat percentage. For example, a waist over 35 in women and 40 in men is considered unhealthy.

What are Prescription Weight Loss Medication Side Effects?

As with many prescription medications, there is a potential for weight loss medications to cause side effects. While these side effects are generally mild and temporary, it’s important to be aware of your individual risk. If you have a history of high blood pressure, heart disease, irregular heartbeat, or stroke, for example, you’re at an increased risk for complications with some appetite suppressants. People who are taking fat absorption inhibitors should eat a low-fat diet and take a daily multivitamin in order to decrease their risk for unpleasant side effects.

What are the Side Effects for Appetite Suppressants?

Side effects for appetite suppressants include:

  • Increased heart rate
  • Increased blood pressure
  • Sweating
  • Nausea
  • Constipation
  • Diarrhea
  • Insomnia
  • Excessive thirst
  • Lightheadedness
  • Drowsiness
  • Headache
  • Anxiety
  • Dry mouth

What are the Side Effects of Intestinal Peptides?

Side effects of intestinal peptides include:

  • Nausea
  • Headache

What are the Side Effects of Fat Absorption Inhibitors?

Side effects for fat absorption inhibitors include:

  • Abdominal cramping
  • Flatulence
  • Oily stool
  • Inability to control bowel movements; leakage of oily stool

Because obesity is a chronic disease, weight loss drugs may need to be used on a long term basis. Most people will notice a plateau in their weight loss after six months on prescription weight loss medications. It’s important, then, that people who are taking weight loss medications use this time to develop new eating and exercise habits if they want to continue to lose weight and keep the weight off in the long-term.

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