Dr Tommy Wood, a neuroscience professor, warns that rapid weight loss while using GLP-1 medicines such as Ozempic and Wegovy may leave the brain short of energy and nutrients if people severely restrict their food intake. He says the drugs can also benefit brain health when they improve obesity-related risks such as high blood sugar and blood pressure, so the effects depend partly on how weight loss is managed.

Wood says prolonged under-eating could deprive the brain of omega-3 fats, iron and protein, while some muscle-size loss may reflect reduced fat within muscle rather than declining strength. He recommends resistance training twice a week and adequate intake of nutrients including B vitamins, vitamin D, iron and omega-3s. He cites research in which marathon runners’ brain white matter temporarily shrank during exertion and recovered after rest and refuelling.