According to [Wikipedia](http://en.wikipedia.org/wiki/Vegetarianism),

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> Vegetarians tend to have **lower body mass index**, **lower levels of cholesterol**, **lower blood pressure**, and **less incidence of heart disease, hypertension, type 2 diabetes, renal disease, osteoporosis, dementias,** [and lower risks of] **cancers of the esophagus, liver, colon, and the lungs.** [...] A 2010 study [showed] vegetarians scored **lower on depression tests** and had **better mood profiles**.
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Of course, correlation =/= causation - *all* of this can be explained by the fact that people who eat only (or just more) vegetables tend to be more health-conscious in other ways: eat better, sleep more, exercise more, less likely to smoke or drink alcohol/caffeine, etc.

**Are there any studies which show positive causal effects of giving up meat,** or is this all just correlational propaganda?

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I always hear vegetarians talk about how when they gave up meat, they suddenly felt their body and mind working so much better. I've been eating a strict vegetarian diet for three weeks now, and the only thing that's working more are my bowels.