A thick waistline can give you diabetes, heart disease, joint problems, and cause stroke, but now a new study says being overweight in midlife also raises the risk of Alzheimer’s disease, and at an earlier age. 
Researchers at the National Institutes of Health announced that being overweight or obese at age 50 puts people at greater risk of developing Alzheimer’s disease early.
“Maintaining a healthy BMI at midlife is likely to have long-lasting protective effects,” said Dr. Madhav Thambisetty of NIH’s National Institute on Aging, who led the study reported in the journal Molecular Psychiatry.
Alzheimer’s affects about 5 million people in the US, but the population is aging, and that number is expected to double by 2050, barring a medical breakthrough.
Typically, it takes a decade for the symptoms of Alzheimer’s to begin to show. There is no known ‘cure’ for the disease, but scientists are working on ways to at least delay it, including offering lifestyle guidelines. Though real-life cases have shown a noteworthy connection between coconut oil and Alzheimer’s prevention.
For the study, Dr. Madhav Thambisetty of NIH’s National Institute on Aging, who led the study reported in the journal Molecular Psychiatry, and colleagues looked at the Baltimore Longitudinal Study of Aging. The study is one of the longest-running projects to track what happens to people as they age. The team analyzed the records of nearly 1,400 participants who had undergone regular cognitive testing every year or two for approximately 14 years, 142 of which developed Alzheimer’s.
The researchers looked at how much those Alzheimer’s patients weighed when they were 50 and still cognitively healthy, and tracked their body mass index (BMI). Every step up on the BMI chart predicted that when Alzheimer’s eventually struck, it would be 6½ months sooner. For example, an obese person with a BMI of 30 at age 50 on average had Alzheimer’s strike about a year earlier than someone whose midlife BMI was 28, in the overweight range.
The threshold for being overweight is a BMI of 25.
The scientists couldn’t track whether the patients’ BMI fluctuated before or after age 50, and had no way of knowing whether losing weight after that age influenced dementia risk.
Brain scans during life and autopsies after death were performed on some of the Baltimore Longitudinal study participants. Both revealed that people with higher midlife BMIs also showed more of the “brain-clogging” hallmarks of Alzheimer’s years later, even if it didn’t develop into full-blown dementia.
Now, scientists want to figure out if staying trim during middle age may have the opposite effect. But regardless, staying a healthy weight can’t hurt you.
“What’s good for your heart is good for your brain,” Heather Snyder of the Alzheimer’s Association, who wasn’t part of the study, noted.
 NBC News