Common sense isn’t common, at least with healthy behaviours. The vast majority of us know that we should eat sensibly, be a reasonable weight, exercise regularly, not abuse alcohol, and avoid smoking. Do you know what percentage of people actually follow all this obvious advice? A survey (Reeves and Rafferty 2005) of over 153,000 US adults in 2000 found that only 3% ticked all four boxes when asked if they didn’t smoke, were a healthy weight (body mass index, calculated as weight in kilograms divided by square of height in meters, 18.5 to 25.0), consumed 5 or more portions of fruit and vegetables daily, and exercised in leisure time for at least 30 minutes, 5 or more times per week (this includes brisk walking).