The effect of exercise on depression

Stress triggers an increase in cortisone, a hormone that keeps the body ready to fight or flight. The persistence of stress and cortisone reduces the level of BDNF (brain-derived neurotrophic factor) and might cause the reduction of hippocampus.

An atrophy of hippocampus  - amongst others, in turn, is related to chronic depression. Studies identify a link between the low level of BDNF and depression.

Exercise is generating an increase in BDNF, and consequently has a positive influence over depression.

More, a reduced level of BDNF is associated with an increased appetite, which might lead to obesity.

Today's formula:

exercise => increase in BDNF => 1. less depressive episodes

                                                        2. reduces appetite => less risk for obesity

Reference:

1. http://en.wikipedia.org/wiki/Brain-derived_neurotrophic_factor

2. an interesting point of view:

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