Can stress make us fat?

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There’s a general view that overweight and obesity are the result of eating too much and/or not exercising enough. Essentially, the idea here is that obesity is the result of greed and/or laziness. I am sure these this may be true for some people. I am also sure that this thinking is over-simplistic and does not adequately explain why some people are over-fat.

We know, for instance, that the accumulation of fat is under a degree of hormonal control. A central player here appears to be insulin, which both promotes the manufacture of fat in the body and, at the same time, slows the rate at which fat is broken down. So, it is possible for individuals to accumulate excess fat not because they eat too much per se, but because they eat foods that precipitate the secretion of lots of insulin (high glycaemic index carbohydrates are a major culprit here).

Another example of the role that hormones play in obesity concerns the thyroid gland. This organ sits in the neck and makes certain hormones that stimulate the metabolism. However, if insufficient quantities of these hormones are produced, the metabolism can stall, and that can make it very difficult for individuals to generate energy from food. Fatigue is a common consequence of this, as is weight gain.

I have during my time in practice seen many people (usually women) with low thyroid function that claim that how much they eat has little or no influence on their weight. Some cynically minded individuals may take the view that they must be lying. I’m sure some people are not as truthful as they could be sometimes, but generally speaking I trust my patients to tell me the truth and I take them at face value.

The idea that body fatness might heavily influenced by hormonal factors was further reinforced by a study published recently in the journal Obesity [1]. This study focused on obese women who experienced rapid weight gain after a stressful event. These ‘stress related obesity’ (SRO) women were compared to another group of women who were obese, but did not report rapid weight gain after a stressful event (Non-SRO). A third group of non-obese women were used for comparison too.

All the women in this study had the amount of the hormone cortisol in the urine measured over a 24-hour period. Cortisol is a major stress hormone, and is known to have the capacity to induce fatness (as well as muscle wasting). The SRO group were found to make and excrete higher levels of cortisol compared to the Non-SRO and non-obese women. Also, higher levels of cortisol were found to be associated with greater weight gain, and more rapid weight gain too. The authors conclude that These findings support the concept that SRO has distinct pathophysiological mechanisms.

In short, this study suggests that higher levels of cortisol, in response to stress, may be a predisposing factor in excess fatness. In other words, stress might make some people fat. It’s another example of how excess body fatness might be the result of influenced by wonky hormones, and not just the result of someone eating too much or not exercising enough.


1. Vicennati V, et al. Stress-related Development of Obesity and Cortisol in Women. Obesity 2009;17(9)1678″1683

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