Weight loss drugs have become very popular in the last year, helping some lose dramatic amounts of weight, but not all of that weight is fat.
Part of that is actually lean mass, which is everything that’s not fat in the body, including bones, organs, and most importantly, muscles.
“When we look at weight loss with any intervention, about a third of the weight we lose tends to be lean mass, and that can be problematic,” said Dr. Jaime Almandoz, an associate professor of internal medicine in the Division of Endocrinology. at the UT Southwestern Medical Center in Dallas. That loss of lean mass is generally from muscle. «Lean mass is healthier and is associated with better metabolism, so when we lose lean mass, we may lose some of that function.»
The more muscle mass a person has, the better the resting metabolic rate, or the number of calories a person burns at rest. When a person loses muscle mass, the resting metabolic rate also decreases.
«If you can maintain your muscle mass, you could have more sustained weight loss because your metabolic rate wouldn’t drop,» said Dr. Louis Aronne, director of the Comprehensive Center for Weight Management at Weill Cornell Medicine in New York.
Two drugs in particular have taken off for weight loss: semaglutide and tirzepatide. Semaglutide is the drug found in Novo Nordisk’s Ozempic and Wegovy; Tirzepatide is the drug in Eli Lilly’s Mounjaro. The drugs work in slightly different ways, but both suppress appetite, causing people to consume fewer calories.
Losing weight has complex effects on the body, especially during the initial phases. The more weight a person loses over a short period of time, the more muscle mass they lose as well as fat, Almandoz said.
When the body doesn’t get as much energy from food, it uses energy stores stored in the form of fat and muscle, starting primarily with fat. While it is normal for some of this extra energy to be drawn from the muscles, the body may need to draw more energy from the muscles if a person is losing a significant amount of weight rapidly, such as 5 to 10 pounds a week in place of about 2 lbs. .
«That’s why we try to emphasize slow, steady weight loss rather than rapid weight loss, where you’re more likely to draw on your energy stores» in muscle, said Dr. Jonathan Purnell, an endocrinologist and professor of medicine at Oregon Health. and the Knight Cardiovascular Institute of the University of Science in Portland. Purnell has done consulting work for Novo Nordisk, according to the Centers for Medicare & Medicaid Services.
«It’s also a function of how low you go,» he said. «Once you get into the healthy BMI range, you’re more likely to be pulling from the lean stores.»
Why is muscle mass important?
Despite concerns about loss of muscle mass, by the end of the period of dramatic weight loss, people may have a healthier body composition, that is, the ratio of lean mass, especially muscle, to fat.
«While the loss of lean mass is concerning, in the end, you may end up with slightly more lean mass compared to other components, such as body fat,» said Almandoz, who has worked as a consultant for Novo Nordisk and Eli lilly.
That’s important because «the damage from obesity comes not from increased muscle, but from increased fat mass, particularly in the abdomen,» according to Aronne, a consultant at Eli Lilly. Figuring out how to lose fat but not muscle would be the «holy grail» of weight loss, she said.
TO clinical trial 2021 that evaluated the weight-loss effects of Wegov and found that while about 40% of the weight people lost tended to be lean mass, including muscle, at the end of 68 weeks, people taking the drug had a lower risk of heart disease and better fitness. function compared to a placebo group.
«Although lean body mass, which includes muscle mass, decreased in absolute terms, the ratio of lean body mass to total body mass increased,» Allison Schneider, a spokeswoman for Novo Nordisk, the maker of Wegovy and Ozempic. .
The studies showed similar results for the drug tirzepatide, which is sold under the brand name Mounjaro. in a phase 3 clinical trial«A reduction in lean mass was reported at a rate similar to that seen in lifestyle-based obesity treatments,» Jessica Thompson, a spokeswoman for tirzepatide maker Eli Lilly, said in a statement sent by email.
A new analysis of data from the same trial found that after 72 weeks of taking the drug, about 25% of the weight lost by the participants was lean mass. However, the participants had a healthier overall body composition. Aronne, who worked on the trial, presented the findings this week at the European Congress on Obesity in Dublin. The analysis has yet to be published in a peer-reviewed journal.
How to maintain muscle mass when losing weight
There are ways to mitigate the loss of lean mass during weight loss, and people over 60 who are already more prone to muscle loss should be especially mindful of building muscle, said Dr. Juliana Simonetti, co-director of the Comprehensive Weight Control Program at the University of Utah in Salt Lake City.
One way is to make sure you’re eating enough protein, which can be hard to do while you’re using weight-loss medications. Protein is the building block of muscle; without enough of it, muscles cannot build and repair themselves.
People should aim to get 60 to 80 grams of protein every day, which can be difficult to achieve through diet alone, Purnell said.
Simonetti said she recommends looking for protein supplements, such as protein powders, that are low in sugar and have at least 20 grams of protein per serving.
Exercise, specifically resistance training, is also a critical part of maintaining muscle mass during weight loss, he said.
Latest news on weight loss drugs
- States threaten to crack down on copied versions of Ozempic and Wegovy
- Some people who take weight loss drugs say they are experiencing hair loss
- Shortage of Ozempic? Some pharmacists choose not to stock the medication at all.
To complicate matters, it’s hard to tell if you’re losing weight from fat or muscle without special equipment. That’s why people taking these drugs should stay in close contact with their health care team, Simonetti said. If you’re losing weight at a rapid rate, chances are you’re also losing muscle mass.
“People need to have a medical team involved when using these drugs so that they can manage not only loss of muscle mass, but also kidney function, salt and electrolytes,” all of which can be affected by weight loss. drastic, he said. Nausea, a common side effect of weight-loss drugs, can also indicate acute kidney failure if a person doesn’t drink enough water, she added.
There are currently no guidelines for physicians advising patients on weight loss medications. For now, many doctors, including Purnell, base their recommendations on guidelines for bariatric surgery patients, since the weight-loss effects of surgery are comparable to those seen with newer weight-loss drugs.
Almandoz said that since the drugs can cause dramatic weight loss, doctors need research-backed recommendations on whether or not to tell people taking the drugs to take extra vitamins or other nutrients. It is also not clear how these recommendations may be different for older people.
“There are many unknowns with these drugs, but we know they are effective and provide metabolic benefits and quality of life improvements,” he said. Continue NBC HEALTH in Twitter & Facebook.