A body mass index (BMI) of 30 or higher—which is an indicator of obesity—increases the risk for ischemic strokes by 50 to 100 percent, according to a 2021 guideline from the American Stroke Association.

Women between ages 20 and 49 who are overweight (with a BMI of 25 to 29) are 1.8 times more likely than people of normal weight to develop dementia later in life, according to a 2021 study in Alzheimer's & Dementia. For obese young women, the odds are 2.45 times higher. A 2019 study in Annals of Clinical and Translational Neurology found that obesity may contribute to the development of MS.

Moreover, scientists have learned that belly flab, especially in the midsection, can promote inflammation, says Eva Feldman, MD, PhD, FAAN, endowed professor of neurology at the University of Michigan Medical School in Ann Arbor. The release of inflammatory chemicals from abdominal fat may damage brain tissue, says Dr. Feldman.

Animal studies done by Dr. Feldman and her colleagues have shown that neurons can develop insulin resistance, which appears to play a role in cognitive decline, Alzheimer's, Parkinson's, and other neurologic disorders, she says. When neurons develop insulin resistance (the main cause of type 2 diabetes), they use glucose less efficiently.

It's clear that maintaining a healthy weight is good for body and mind. But losing weight can be challenging. These strategies may help.