Is adiposity responsible for the loss of brain cells?

A new study shows that adiposity apparently increases the risk for dementia. The connection between the two diseases is more complex that previously assumed.

In Germany currently more than one million people suffer from the loss of their intellectual capacity. Two-third of them has to deal with the Alzheimer illness- the most frequent type of dementia. Every year there are 250 000 more people that suffer from an Alzheimer disease due to the high population age. In this country dementia has become a common illness that should be taken seriously. However, it could not be cleared yet how exactly the brain cells come to die.

Numerous studies have pointed that also adiposity and the related cardio-metabolic diseases like high-blood pressure and diabetes increases the possibility to suffer from dementia in higher age. Therefore, it needs to be questioned how and in what way overweight effects brain functions.

It seems to be proved: obesity increases the risk for dementia. Latest studies have showed that overweight is not without consequences for the intellectual capacity: already people at the age of 40 till 50 with a body mass index (BMI) of 30 or more kg/m² have shown tremendous intellectual reductions-apparently due to their obesity. This is the result of a long-term study of the Institute National de la Santé et de la Recherche Médicale (INSERM) in Paris. The researchers have accompanied over 6400 adults for about ten years and collected and evaluated their data in different metabolic as well as in cognitive tests. All participants were between 39 and 69 years old and took part in different examinations in which their strength of language, intellectual capacity and their memory were tested every five years.

More over, the researchers included metabolic measurands, like data over cholesterol level, plasma lipid concentration, high-blood pressure and diabetes type II. The researchers defined a divergent metabolic status if the participants had fallen ill with at least two of the mentioned parameters. 31 per cent of them therefore suffered from one of the mentioned metabolic disorders. 38 per cent of the participants were overweight, nine per cent of them even obese. In addition to this, the obese test persons were subdivided 'metabolically striking' as well as in 'obese healthy'. e. they suffered from none of the mentioned metabolic disorders although they were strongly overweight.

Finally, an astonishing result arose after all examinations: both obese participants with metabolic sufferings and obese healthy people had showed a similar reduced brain function during the complete examination time. The scientists came to this conclusion after they had calculated the speed of mental breakdown for the entire study period. Therefore obese people have a poorer brain function than non-obese ones even if they were not suffering from any parallel metabolic disorders. So far, scientists had assumed that an increased risk of dementia in obesity is due to the concomitant metabolic disorders. But being overweight can actually shrink your brain?

Dr.  Annette Horstman from the Max-Planck Institute for Human Cognitive and Brain Science explains how body size can affect cognitive performance. Together with the Integrated Research and Treatment Centre (IFB) AdiposityDiseases she explores the links between obesity and changes in brain structure and behaviour of obese people: 'We could, depending on the severity of obesity in young people, show changes in brain structure. These changes went with behaviour differences between obese and normal weight subjects associated in a game task. How far our results show an outcome of the overweight or a cause of it is completely unclear so far. To answer this question, we must make long-term studies.’

That means, obesity doesn’t lead to dementia mandatorily, however, it is involved in the changes of brain activities. ‘Further studies need to be carried out, in which factors such as genes, the duration of overweight phase and metabolic disease as well as environmental factors are taken into account’, states the scientist.  Only then, it is possible to make more precise statements about the interaction between weight and brain function. To be notes until then: Those who are physically healthy are also more productive with their head.