Most people know these new effective weight loss drugs by their trade names: Ozempic, Wegovy and Mounjaro. Ozempic and Wegovy are different names for semaglutide. Mounjaro is the trade name for tirzepatide. All of these drugs are in the same class. They are called GL-P1 agonists. They mimic the action of a hormone called glucagon-like peptide. These drugs were developed to treat type 2 diabetes. They lower blood sugar by causing insulin release and also by delaying stomach emptying, which delivers less glucose to the bloodstream. The slowing of emptying from the stomach decreases appetite and causes an increased feeling of fullness. People on these drugs tend to reduce their calorie intake fairly markedly and that is how they work for weight loss.

Common Side Effects

The most common side effects of all these long acting medicines are nausea, vomiting, abdominal pain and diarrhea. These side effects usually disappear within a few weeks, and are less likely to happen if they are started at a low dose and increased gradually. Occasionally they are persistent. Some somewhat less common side effects include headache, fatigue, dizziness, constipation, heartburn, bloating, belching and flatulence (passing gas). People with diabetes can sometimes get low blood sugar. Again, most of these side effects usually go away within a week or two. Occasionally they can be persistent.

Rare Side Effects

These side effects are rare, but much more serious and can result in hospitalization. They include severe allergic reaction, acute pancreatitis, gall stones, acute kidney injury, suicidal thinking, and cancer of the thyroid.

Long Term Effects

The evidence so far is that stopping these medicines results in weight gain back to the original weight. That means that people are likely to have to stay on these medicines to maintain the weight loss. We know that the medicines are relatively safe when taken for two years, but we have no idea what long term side effects might be, or even if the medicines will continue to work past two years.

How well do they work?

The medicines are given by injection once a week and they work very well. These are the most effective medicines for weight loss that we have ever had, and there are some new ones in the pipeline that may even work better. As with any medicine, there are risks as I have documented above as well as benefits. You would not want to take one of these medicines unless the benefit exceeds the risk.

Who should take these medicines and who should not?

Obesity increases the risk of diabetes, heart disease and cancer, especially colorectal cancer. The best predictor of risk of disease from obesity is the waist circumference. Just take a tape measure and measure your waist at the level of the belly button. If you are female your risk of cancer starts to increase if your waist circumference is more than 31.5 inches. Your risk of cancer, especially colorectal cancer increases 5% for every inch above 31.5 inches. Above 35 inches the risk of diabetes, and cardiovascular disease starts to go up. For men the numbers are 37 inches for the risk of cancer going up and 40 inches for the risk of diabetes and cardiovascular disease.

The best treatment for obesity is prevention. That means eating unprocessed foods and regular exercise. If you are already overweight or especially if you are obese, it is very hard to lose weight and keep it off. Once you lose weight, your body thinks it is starving and all kinds of hormones and body changes kick in to try to get the weight back.

If your waist circumference is over 31.5 if your are female and 35 if you are male, then you are a candidate for one of these new weight loss medicines. For you the benefit likely outweighs the risk. If your waist circumference is less than those values, then the risk of taking these medicines is much higher than the potential benefit.

Cost

If your insurance does not cover medicines for weight loss the cost of these medicines may be prohibitive.

Wegovy costs $1,349.00 a month without insurance.

Ozempic costs $892.00 a month without insurance.

Muanjaro costs $1,300 a month without insurance.

Unfortunately many insurance plans do not cover weight loss medicines.