What is the single best thing we can do for our health?

I am basically a lazy person but I knew that my poor diet and sedentary lifestyle were catching up with me. In addition to discussing this with medical and allied health professionals I did what a large percentage of people do these days - I turned to the internet. I had been following Fraussie's Aussie in France blog so was thrilled when she started her 'How I lost 20 kilos after 50 for good' series of posts. If she could do it, then perhaps I could do it too. Just the inspiration I needed to get started. I am heading to France in a few months time and I want to be fit and well enough to make the most of my time there.

It all seemed overwhelming. Where should I start? What would have the biggest impact to improve my health? More internet searches and I came across the video from Dr Mike Evans on You Tube. He examines in a clear, succinct and entertaining manner 'What is the single best thing we can do for our health'. He is founder of the Health Design Lab at the Li Ka Shing Knowledge Institute, an Associate Professor of Family Medicine and Public Health at the University of Toronto, and a staff physician at St. Michael's Hospital. There is mention that they may do Spanish and French versions in addition to the English and Italian ones currently offered.

What is the single best thing we can do for our health (English version):

I have started following guidelines given to me by a dietician, noting down what I am eating, walking and drinking water. I confess that I used to go for weeks on end without drinking any water. Diet cola drinks are my preference but not something that I recommend. They are not a healthy alternative and from what I can tell are full of chemicals. I am not expecting this journey to be an easy one but it is definitely one that I need to do.

What is the single best thing we can do for our health (Italian version):