As if we needed more evidence. Here it is in black and white. Lifestyle changes could prevent a huge amount of cancers. http://www.msnbc.msn.com/id/41426537/ns/health-aging/
This means eating healthier food, drinking less alcohol and being more physically active. So how appealing does that quadruple cheese and bacon lardburger sound - when it could be the very burger that triggers the first cancerous cell in your body that survives to multiply???
We don't have to be as physically fit as an Olympic marathoner, nor a strict low fat vegan (which is, incidentally, the gold standard of healthy eating), or as sober as a judge. That would be an all-or-nothing definition e.g. "I can't become a marathon running, non-drinking vegan, so I won't even bother trying". ANY steps you take towards the more health-supporting end of the spectrum will do you good.
So get off your rear, step away from the laptop and take a walk around the block. Then eat an apple. The journey of a thousand miles begins with one step.