You are constantly seeing articles about studies showing that if you do X, then Y happens. Last week the Press made too much of an epidemiologic study in BMJ Open "showing" that...

1. Cutting TV viewing to less than 2 hours per day extends life by 1.4 years.
2. Sitting 3 hours less each day adds 2 years to lifespan.

It may be true or it may not, but the study did not SHOW it. Epidemiological or population studies cannot prove such a thing; only prospective randomized controlled trials can. Read my book Medical Myths Doctors Believe, available on amazon.com or Kindle, to learn the difference.