The study looked at the specific relationship between the amount of body fat and the risk of depression
Carrying ten kilograms of excess body fat increases the risk of depression by seventeen per cent and the more fat, the greater the probability of developing depression, these are the conclusion from a new study by researchers from Aarhus University and Aarhus University Hospital, Denmark.
“Our study also indicated that the location of the fat on the body makes no difference to the risk of depression. This suggests that it is the psychological consequences of being overweight or obese which lead to the increased risk of depression, and not the direct biological effect of the fat,” said the study’s last author, Dr Søren Dinesen Østergaard, professor at the Department of Clinical Medicine at Aarhus University and affiliated with the Department of Affective Disorders at Aarhus University Hospital. “If the opposite was true, we would have seen that fat located centrally on the body increased the risk the most, as it has the most damaging effect in biological terms.”
Prior studies in the field have predominantly used BMI to measure obesity, but that does not, take build and muscle mass into account. This latest paper, ‘Investigating the association between body fat and depression via Mendelian randomization’, was published in Translational Psychiatry.
“BMI is an inaccurate way of measuring overweight and obesity. Many elite athletes with a large muscle mass and a low body fat mass will have a BMI above 25, which is classified as overweight according to the common definition,” explained Østergaard. “This obviously doesn’t make much sense. Therefore, one of the strengths of our study is that we’ve been able to zoom in and look at the specific relationship between the amount of body fat and the risk of depression.”
In the study, the researchers have analysed data from two large genetic data sets: the UK Biobank, which contains data on the correlation between genetic variants and physical measurements (including body fat mass distributed around parts of the body); and the Psychiatric Genomics Consortium, which contains information on the correlation between genetic variants and depression.
Genetic epidemiological study utilising data from the UK Biobank (with information on the association between genetic variants and fat mass based on a study of 330,000 people) and the Psychiatric Genomics Consortium (with information on the association between genetic variants and depression based on a study of 135,000 people with depression and 345,000 control subjects).
Østergaard also highlights his research group’s choice of the ‘Mendelian randomisation’ method as the main reason why the study was successful. He also emphasises that the findings are particularly significant in light of the fact that almost 40 per cent of the world’s adult population is overweight.
“In addition to the known physical consequences of obesity such as diabetes and cardiovascular disease, there is also a significant and now well-documented psychological component, which needs to be dealt with as well. This is yet another argument for resolving the obesity epidemic,” he explained. “As it appears to be the psychological consequences of obesity, such as a negative body image and low self-esteem that is the main driving force behind the increased risk of depression, society’s efforts to combat obesity must not stigmatise, as this will probably increase the risk of depression even further. It is important to bear this in mind so we can avoid doing more harm than good in the effort to curb the obesity epidemic.”