This study examined whether obesity was associated with onset of significant depressive symptoms in a large community-based sample of older, initially non-depressed, persons during 5 years of follow-up. The results showed that in men but not in women obesity increased the risk of onset of significant depressive symptoms. Specifically, abdominal obesity appeared to be associated with the onset of depressive symptoms, independent of and more consistently than overall obesity. Men with high visceral fat had a more than 2-fold increased risk of becoming persistently depressed compared to men with normal amounts of visceral fat. Moreover, results showed that in men almost 10% of depressive symptoms onset and 20% of persistent depressive symptoms onset was related to having high visceral fat.
Several studies indicated that obesity and depression are associated2–4
. However, as concluded by Atlantis and Baker1
in their systematic review on obesity and depression, few studies have investigated the temporal direction of this association. Our findings correspond to a study by Roberts et al.10
which showed among persons aged 50+ that obesity at baseline was associated with an increased risk of depression 5 years later. Our results additionally showed that associations with depressive symptoms appear to be more consistently related to abdominal obesity than to overall obesity. The association between depressive symptoms and overall obesity in men was not consistently found after adjustment for visceral fat, while the association with visceral fat remained after controlling for BMI. At least, these results show that abdominal obesity has an additional effect on depressive symptoms onset above the influence of overall obesity. These results are in line with other studies showing that in particular abdominal obesity, more than overall obesity, is associated with poor health outcomes, such as diabetes and CVD13;14
To our knowledge, the current study was the first to test and demonstrate that abdominal obesity increases the risk of onset of significant depressive symptoms in men. This evidence should be considered together with other recent longitudinal results which illustrates that – the other way around – depressive symptoms also lead to increases in abdominal obesity over 5 years9
. The fact that abdominal obesity and depressive symptoms are found to be reciprocally associated, indicates that the two are strongly intertwined and suggests that a vicious cycle might exist. The bidirectional relationship between abdominal obesity and depressive symptoms further indicates that when trying to break this vicious cycle, treatment of either obesity or depression cannot be given in isolation and comorbidity between these two should be taken into consideration.
How might abdominal obesity increase the risk of incident depression? First, a poor self-image or perceived stigma of an obese person might induce depression20
. Also, binge-eating behavior, not uncommon in obese persons, has been associated with major depressive disorder21
. These mechanisms are probably true for overall obesity as well as and not specific for abdominal obesity. Poor lifestyle behaviors might lead to both abdominal obesity and depression. However, in our analyses adjustment for lifestyle behaviors did not influence results much. In addition, diseases related to abdominal obesity such as diabetes and CVD have been associated with depression22;23
and might be responsible for the association between abdominal obesity and depression. In our study, adjustment for prevalent as well as incident diabetes and CVD did not affect the relationship between abdominal obesity and depressive symptoms onset, suggesting that such an association does exist rather independently of diabetes and CVD. Other pathophysiological explanations may exist. Studies have shown that visceral fat produces cytokines in higher amount than subcutaneous fat24
. High levels of cytokines such as TNF-alpha, IL-6, and C-reactive protein have been found both in visceral obesity25
. In addition, the mechanisms discussed above (poor lifestyle, more diabetes and CVD, and inflammation in obese persons) might all induce vascular damage and are therefore in line with the vascular depression hypothesis, which states that vascular damage in the brain might predispose, precipitate, or perpetuate depression in the elderly27
. Also, a dysregulation of the hypothalamic-pituitary-adrenal axis28;29
and sex steroid hormones30;31
have been found to be involved in both abdominal obesity and depression, and could be linking mechanisms.
The link between abdominal obesity and significant depressive symptoms was restricted to men. A reason for this could be due to the fact that men have more visceral fat than women. If the amount of visceral fat is important for negative health effects to emerge, than men will be more at risk to experience such negative health effects. In addition, this is an aging population in which losses of (visceral) fat over time are not uncommon especially in women32
, which might leave women at a smaller risk of visceral fat to cause poor health. Another explanation might be that in women the relative contribution of visceral fat to depression onset is small due to a larger influence of competing risk factors. For instance, insufficient social support and stressful life events have been found to pose a greater risk for depression among women compared to men33;34
. Although previous cross-sectional studies that examined sex differences predominantly showed stronger results for women in the association between overall obesity and depression3;12
, one study reported an association between depression and abdominal obesity only in men2
. Future research should explore these sex differences further in younger samples to eliminate counteracting effects of aging.
Our study has some limitations. We did not have well-defined DSM-IV-based depression diagnoses. However, the CES-D is a commonly used scale to assess clinically significant depressive symptoms. In addition, since we had no information on history of depression, depressive symptoms onset might represent recurrence of an earlier depression in life. Therefore, results do not necessarily indicate incidence of a first depression episode in life, which is less common in later life, but do reflect a new occurrence of depressive symptoms during later life. Our study also had some important strengths including a large sample with longitudinal assessments of depressive symptoms. In addition, DXA and CT scans were performed, which assess total and visceral fat stores directly and we were able to compare them with more commonly used anthropometric measures.
In all, our findings indicate that the strength of the association between abdominal obesity and depressive symptoms is of both clinical and public health relevance. Men with visceral fat levels in the highest quartile (≥194 cm2
) had almost 35% more chance of becoming depressed over 5 years than men with normal amounts of visceral fat. The risk of becoming persistently depressed was more than 2-fold for men with high visceral fat. We found that the size of this effect was at least equal to the difference in the onset rate of depressive symptoms between men and women. A 35–40% increased risk of incident depression for women vs. men is comparable to what has been found in other studies among older persons35
, and is normally considered to be an important predictor for depression onset. In contrast to sex, however, high visceral fat is potentially modifiable and it is tempting to consider the possibility that weight reduction might reduce the onset of new depressive symptoms. Future research should investigate whether visceral fat reduction indeed can prevent onset of depressive symptoms.
In conclusion, our results suggest that, in older men, obesity relates to the onset of significant depressive symptoms. Abdominal obesity appears to be more consistently associated with depressive symptoms onset than overall obesity or at least shows an additional effect above overall obesity. These findings strengthen the idea that specific properties of visceral fat might give rise to depression. The impact of the association between abdominal obesity and onset of significant depressive symptoms on public mental health seems to be of great enough importance to warrant additional research that confirms our findings and explores underlying mechanisms. When known, this might have direct implications for depression treatment and prevention.