A weekly injection that leads to dramatic weight loss without serious side effects almost sounds too good to be true. But several drugs originally developed to treat type 2 diabetes can help people shed as much as 20% of their body weight — far more than other anti-obesity drugs. Known as incretin mimetics, they also improve blood pressure and cholesterol levels.
Not surprisingly, these medications are in high demand, especially semaglutide (for a list of these drugs and their brand names, see "Diabetes and anti-obesity drugs"). This has led to shortages of certain formulations. That’s just one of the issues faced by people hoping to take these drugs, which are costly — around $1,000 to $1,500 per month — and not covered by Medicare for obesity (although some private insurers cover them). Who’s a good candidate for these medications, and what else should people know about them?
Diabetes and anti-obesity drugs
Poisonous lizards known as Gila monsters have a unique ability to maintain steady blood sugar levels even after long stretches of not eating. Venom from this colorful creature inspired the development of exenatide (Byetta), the first in a class of drugs known as incretin mimetics.
Today, there are more effective drugs that mimic an incretin called GLP-1. These injectable drugs include dulaglutide (Trulicity), liraglutide (Victoza), and semaglutide (Ozempic); the latter is also available as a pill called Rybelsus. Liraglutide and semaglutide are also approved for weight loss, in formulations marketed respectively as Saxenda and Wegovy.
The newest addition to this drug family combines GLP-1 and another incretin mimic, GIP. Tirzepatide (Mounjaro) was approved for treating type 2 diabetes in May 2022 and tagged for accelerated review for approval to treat obesity, which is anticipated sometime in 2023.
Up to half of all new-onset diabetes cases in this country are linked to obesity, a disease that now affects more than 40% of Americans. Both conditions are closely linked to cardiovascular disease. "Many cardiologists now recognize that treating obesity is the best way to treat heart disease," says Dr. Caroline Apovian, who co-directs the Center for Weight Management and Wellness at Harvard-affiliated Brigham and Women’s Hospital.
Other anti-obesity drugs help people lose only about 5% to 8% of their body weight. But the incretin mimics, which are similar to hormones made naturally by the gut and brain, have multiple effects. They prod the pancreas to release insulin when blood sugar rises too high, slow down the emptying of the stomach, and target brain receptors involved in reducing appetite.
The newest ones, tirzepatide and semaglutide, can lead to remarkable weight loss and also lower HbA1c levels (a three-month average measure of blood sugar) by as much as two percentage points. "Studies also show that semaglutide and liraglutide, an older drug, can lower the risk of serious cardiovascular problems, such as heart attack and stroke, in people with obesity and diabetes," says Dr. Apovian. A large trial to see whether semaglutide lowers heart-related risks in people without diabetes who are overweight or obese is currently under way, she adds.
Who might consider these drugs?
People with diabetes who are carrying excess weight are good candidates for semaglutide or tirzepatide, especially those at high risk for heart disease, Dr. Apovian says. For people without diabetes, the official criteria for prescribing the drugs are the same as for all other anti-obesity drugs: a body mass index (BMI) of 30 or higher, or a BMI of 27 or higher and at least one weight-related health problem, such as high blood pressure or high cholesterol. (See the calculator at /bmi-calculator to estimate your BMI.)
Taking these drugs involves injecting yourself in the abdomen or thigh using a penlike device with a tiny needle the size of a human hair. Side effects such as nausea, diarrhea, and constipation are common. But they rarely last longer than a week or so, especially if you start low and increase the dosage slowly while guided by an experienced physician, says Dr. Apovian.
If you stop taking the drug, you’ll likely regain weight. But that’s similar to what would happen if you were taking blood pressure medication and stopped — your blood pressure would rise. "Obesity is a disease, and we need to treat it like one," says Dr. Apovian.
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