Obesity is a major public health issue, affecting 300 million people around the world. We already know that obesity is linked to an increased risk of type 2 diabetes, hypertension, stroke and heart disease, And obesity is also known to increase the risk of dementia and Alzheimer’s disease in later life.
Now a study from the University of California, Los Angeles, and elsewhere, points to a possible genetic explanation for the link between obesity and dementia.
A variant of the fat mass and obesity-associated (FTO) gene, which is carried by nearly half of Western Europeans, is linked to a higher body weight and higher waist circumference. In this new study, the FTO variant was also found to be linked to reduced brain volume.
The researchers generated three-dimensional brain maps for a group of 206 healthy elderly people using magnetic resonance imaging. The participants were part of the Alzheimer’s Disease Neuroimaging Initiative. Those found to be carrying the obesity-related FTO variant were also more likely to have a smaller brain volume. In the frontal lobes, the difference was 8% and in the occipital lobe it was about 12%. Those with a higher body mass index were also found to have smaller volumes in these brain regions. These reductions were not related to high cholesterol, or to hypertension. The study was not able to say whether carrying the FTO gene variant actually increased the risk of dementia, but reduced brain volume is a feature of the condition. Though healthy now, those with reduced brain volume might go on to develop dementia.
The researchers discuss whether higher body mass index is capable of altering brain structure and the FTO gene variant somehow strengthens this link. Or, obesity has an effect on brain structure and the presence of the FTO gene variant is a marker of this, as it increases the risk of overweight or obesity. The impact of the FTO gene variant on dementia risk ought to be explored further, as its presence among the population is so common. And lifestyle change can help, for recent research showed that the gene variant had less impact on weight among those who are physically active. This may be true for risk of dementia as well.