The surging popularity of GLP-1 weight loss medications such as Ozempic and Wegovy has brought new attention to how rapid weight reduction and severe calorie restriction may affect the brain. Experts warn that inadequate food intake could deprive the brain of essential energy and nutrients.

Dr. Tommy Wood, a professor of pediatrics and neuroscience at the University of Washington, said the potential effects depend partly on whether people receive sufficient nutrition and energy as they lose weight. He discussed the issue with Fox News Digital at Strong NY, New York City’s largest annual fitness and wellness festival.

"The best way to think about this is the spectrum of what we call energy availability," Wood told Fox News Digital. "The brain is your most energy-hungry organ in the body."

Wood described brain reserve as the physical amount and integrity of a person’s brain tissue. According to him, brain reserve follows a bell shaped curve in relation to how much energy is available to the body.

Too much energy can also create problems. Wood said obesity, high blood sugar and metabolic disease may reduce the brain’s resilience by damaging blood vessels and contributing to insulin resistance.

For people experiencing those conditions, GLP-1 medications can offer cognitive benefits by helping lower blood pressure and improve blood sugar control. But Wood said risks may emerge at the opposite end of the energy spectrum when calorie deficits become extreme.

The brain requires a continuous fuel supply, and severe restriction can leave it without enough energy. Wood pointed to research involving marathon runners to illustrate how intense energy demands may temporarily affect brain tissue.

"There was a study that looked at the brains of people who ran a marathon ... because the marathon is so energy-intensive, the white matter in the brain actually shrank during a marathon because the brain didn't have enough energy … so it was eating its own white matter," Wood said, adding that participants recovered after rest and refueling.

"It just shows that the brain is really energy-hungry, and it will decrease its size if it's not getting enough energy."

Questions about muscle loss among people using GLP-1 medications can be more complicated than they initially appear, Wood said. Some of the early lean mass reduction may actually involve fat that accumulated inside the muscles, rather than a damaging decline in functional strength.

"So technically, your muscles get smaller, but you don't get weaker," he told Fox News Digital. "And the quality and functioning of your muscles actually gets better."

The greater concern arises when people drastically restrict their food intake over an extended period. Chronic under eating may prevent the central nervous system from receiving nutrients needed to support its structure and function.

"It is possible that you can end up going too far," Wood said. "If you're not eating enough, you're not getting the nutrients that are critical for the brain. So you're not getting in enough omega-3 fats, which we know are really important. You're not getting enough iron and protein and all those kinds of things."

Wood identified B vitamins, including B12, folate and B6, along with vitamin D, iron and omega-3 fatty acids, as important nutrients for protecting brain health. Ensuring an adequate intake of these nutrients can help prevent long term cognitive impairment, according to Wood.

He also recommended combining a weight loss regimen with resistance training twice each week. This approach can help preserve functional muscle mass while stimulating brain growth factors, he said.

Wood’s warning does not dismiss the potential benefits of GLP-1 medications. Instead, he emphasized that people should avoid pushing calorie restriction so far that the brain no longer receives enough energy, protein, fats, vitamins and minerals.

"For most people, I think it's going to be beneficial to start, but you just need to make sure that you don't push it too far, that you're now getting enough of everything that the brain needs," he advised.