It's well known that rates of obesity have been rising steadily over the past half century and have reached epidemic proportions. Here's a chart showing just how serious the problem.
Obesity is linked to a whole host of medical conditions, including type 2 diabetes, coronary heat disease, and all-cause mortality. The CDC (Centers for Disease Control and Prevention) estimated the medical costs of obesity in the US at $147 billion in 2008 dollars. Now, a new study has found that excessive body fat, especially around the middle, may also be linked to brain shrinkage.
The researchers measured the BMI and waist-to-hip ratio of 9,652 middle-aged people. BMI is a weight to height ratio, and a BMI of 30 or more is considered obese. Waist-to-hip ratio is measured by dividing the circumference of the waist by the circumference of the hips. Men with a waist-to-hip ratio of 0.9 or more, and women at 0.85 or more, are considered to be centrally obese.
They found that those with high BMI and waist-to-hip ratios had smaller brain volumes than those who didn't have high waist-to-hip ratios. Specifically, their grey matter was 12 cubic centimetres smaller. Grey matter consists of the neurons themselves and are involved in wide variety of functions, including self-control. They also found links between obesity and shrinkage of specific brain areas (the caudate, putamen, pallidum, and nucleus accumbens). These structures are part of the basal ganglia located in the mid-brain and that play an important role in goal-directed behaviour and motivation.
However, because this was a correlational study, it's impossible to tell whether the smaller grey matter volume was responsible for the obesity, or the obesity was responsible for the smaller grey matter volume. Nevertheless, the link between gut health and brain health has now been firmly established. This study is just the latest to support the importance of our physical health to the health of our brain.
Hammer, M. & Batty, D. G. (2019). Association of body mass index and waist-to-hip ratio with brain structure. Neurology, Jan 2019, 10.1212/WNL.0000000000006879; DOI:10.1212/WNL.0000000000006879
Image credit: https://www.flickr.com/photos/73416633@N00/1212880595