Losing weight on GLP-1 drugs such as Mounjaro and Wegovy comes with a caveat: the assumption that eating less is always better can harm brain health, a U.S. researcher warned.
"Losing a Lot of Weight Isn't Automatically Good" — What to Watch
Dr. Tommy Wood, a professor of pediatrics and neuroscience at the University of Washington, said patients taking GLP-1 obesity drugs should monitor not only how fast they are losing weight but also whether they are taking in enough energy and nutrients, Fox News reported on the 2nd.
Wood said the brain is the organ that requires the most energy in the human body, explaining that the volume and health of brain tissue are closely tied to the body's energy supply.
That does not mean GLP-1 drugs are bad for the brain. An excess of energy from obesity, high blood sugar or metabolic disease can also damage blood vessels and raise insulin resistance, reducing the brain's resilience. In those cases, Wood said, improvements in blood pressure and blood sugar from GLP-1 treatment can benefit cognitive function.
The problem lies at the opposite extreme. When appetite is already suppressed by medication and food intake is restricted too severely, the brain can fall short not only of energy but also of essential nutrients such as omega-3 fatty acids, iron and protein.
Marathon Runners Lost Brain White Matter — Long-Term Low Calories Are the Risk
Wood pointed to marathon research as an example of how sensitive the brain is to an energy shortfall.
Studies that scanned the brains of people who had run a marathon, which burns a large amount of energy in a short time, found a temporary reduction in the brain's white matter. Wood explained that when energy ran short, the brain used its own white matter as a fuel source. The participants' brains recovered after they were given adequate rest and energy.
"It shows that the brain can shrink in size if it is not supplied with enough energy," he said.
A marathon causes only temporary energy depletion, but the situation may differ for someone who eats far too little over a long period while on a GLP-1 drug. Chronic undernutrition could leave the central nervous system without the nutrients it needs.
"If you don't eat enough, you're not going to get the nutrients that are important for the brain," Wood said, citing omega-3 fatty acids, iron and protein as prime examples.
Muscle Loss Also Bears Watching: "Two Strength Sessions a Week Recommended"
On concerns about muscle loss during GLP-1 treatment, Wood said the issue requires a more nuanced reading. Some of the lean mass lost in the early stages of weight loss may be fat that had accumulated inside the muscle.
"Technically the muscle gets smaller, but it may not get weaker," Wood said, adding that muscle quality and function sometimes improve.
Still, cutting food intake sharply over a long period can create problems in maintaining actual muscle. He recommended strength training twice a week during weight loss to preserve functional muscle mass and stimulate brain growth factors.
On diet, he advised taking in enough B vitamins, including vitamin B12, folate and vitamin B6, along with vitamin D, iron and omega-3 fatty acids.
"I think starting is probably helpful for most people," Wood said. "But don't push too hard, and make sure you're getting everything your brain needs."
