When it comes to weight, we all know that a physical injury, emotional turmoil, a change in metabolism with age, or a sedentary lifestyle are just some of the ways that a person can go from having a BMI (Body Mass Index) in the normal range to having one in the overweight range before we even realise it. It’s not just those who make poor choices, have issues with impulse control, or are ill-educated about nutrition that can end up packing on the pounds, it can happen to any of us.
But if we stop paying attention -or never paid attention to begin with- once you have gained the weight there are serious consequences to keeping that weight on over time. Obviously there are common side-effects like diabetes and heart disease, but now there has been a study published in the journal Neurology by the American Academy of Neurology that shows gaining and keeping the weight on may actually speed up dementia or other forms of cognitive decline.
Conducted by Dr Maxime Cournot of Toulouse University Hospital in France, more than 2,000 people between the ages of 32 and 62 sat for four different cognitive tests in 1996 and then took the tests again in 2001.
Those with a BMI of 20 (which is considered to be in the healthy range) remembered an average of 9 out of 16 words in a language test, or an average of 56% of the vocabulary. Results from participants with a BMI of 30 (in the range of obese) remembered 7 out of 16 words on average, or only 44% of the vocabulary. The majority of the participants who gained weight between the first and second rounds of tests did not show much change in cognitive function, but those who had a high BMI before the first test and kept the weight on in the years between the first and second test showed higher levels of what Dr Cournot described as “cognitive decline”.
According to the World Health Organisation, BMI is calculated by multiplying your height in meters by itself, and then dividing your weight in kilogrammes by the value calculated by doubling your height. A BMI of 18.5 or less is considered underweight. Normal ranges from 18.5 to 24.9, overweight from 25 to 29.9, and obese is BMI 30.0 and above. While there are some limitations to body mass index calculations, and the method has received some criticism, it is the still the only accessible and consistent tool in use for physicians.
While this research is new and shows correlation rather than causation, and more research needs to be conducted, there are several hypotheses put forward by Dr. Cournot as to the potential cause of these findings. One being that the hormones secreted from fats could have a damaging effect on cerebral cells, resulting in decreased brain function. She also mentioned that insulin resistance could have some connection to lessened cognitive activity. “Another explanation could be that since obesity is a widely known cardiovascular risk factor, due to the thickening and hardening of the blood vessels, that the same happens with the arteries in the brain,” she said.