muffintop-less:

Excessive stress can cause an increase in the secretion of the hormone, cortisol.. which promotes fat storage.
Some studies have shown that stress and elevated cortisol tend to cause fat deposition in the abdominal area rather than in the hips. This fat deposition has been referred to as “toxic fat” since abdominal fat deposition is strongly correlated with the development of cardiovascular disease including heart attacks and strokes.