With an expanding waistline, a worrisome list of health concerns emerges. But for a while now, the jury has come out exactly on how weight gain affects what is between our ears.
A new study suggests that it is not optimal. The research provides strong evidence linking extra body mass – particularly fat transported around the belly – to a troubling decrease in brain volume.
How much this extra fat affects the function of our brain is not clear, but with previous research linking obesity to neurological conditions, this does not seem positive.
"Existing research linked brain shrinkage to memory decline and an increased risk of dementia, but the research on whether extra body fat is protective or detrimental to brain size was inconclusive," says lead author Mark Hamer of the University of Loughborough, England.
Some studies have suggested a decline in some types of brain cells with an increase in body fat levels, showing a potential cause for the increased risk of neurological conditions.
But not all researchers agree with the findings, especially when weight may fluctuate in the years before the diagnosis of dementia.
To try to unravel the details, the researchers in this latest study compared body mass index (BMI) measurements and waist-hip ratio with the volume of signal-bearing nerve tissue called the "gray matter" and the supporting tissue of the " white matter ". .
Each factor was examined on its own earlier – the difference this time was to examine them as a joint effect between waist-hip ratios as well as the IMCs.
A little less than 10,000 participants were involved in the study, ranging in age from 40 to almost 70 years. All participated in a recent "Biobank" survey in the United Kingdom, during which they had their bodies scanned with MRI equipment.
Measurements of height and total body weight were used to calculate a body mass index score – a traditional, though somewhat flawed, indicator of obesity. Body fat masses were also recorded and combined with other details to provide a fat index-mediated score.
Waist and hip circumferences were also measured to arrive at another measure indicative of weight gain.
This gave the research team a database of anatomical information to analyze and compare. Just under one in five of the sample qualified as being obese, most of whom were less likely to be physically active, and more likely to have heart disease and high blood pressure.
Taking into account other factors that could produce differences in brain volume – such as age, smoking and exercise – the team found that body mass index alone could be linked to a slight decrease in gray matter volume.
But having a high BMI with a high waist-to-hip ratio turned out to be the real concern.
About 1,300 people fall into this category. On average, they had a brain volume of gray matter of only 786 cubic centimeters.
In comparison, the 3,000 subjects with healthy BMI and waist-to-hip ratio had an average volume of 798 cubic centimeters, while those with high BMI and relatively thin waist reached 793 cubic centimeters.
While the study may show a relationship, the nature of this link is still under debate. It is possible that excess fat may be affecting the central nervous system through the cardiovascular system.
There is also the usual warning to avoid drawing conclusions about how the relationship is run. Studies like these do not rule out the possibility that the loss of gray matter in some way makes it difficult to lose weight.
Unfortunately, most individuals who were contacted to participate in the research declined. The small proportion that offered itself tended to be a little healthier, which should be kept in mind when considering the results.
Still, research is a compelling argument for closely examining the connection between obesity and neurology.
"We also found links between obesity and shrinkage in specific regions of the brain," says Hamer.
"This will require further research, but it may be possible that someday, regularly measuring BMI and waist-to-hip ratio can help determine brain health."
With so many discoveries linking the physiology of our gut with the functioning of our brain, it is not surprising that body fat and brain volume are somehow connected.
Undoubtedly, the closer we are, the more complex this relationship will be.
This research was published in Neurology.