Guardian: Tradition dictates that this is a difficult time of year. It’s the point where we have to swap the sofa for a sweaty gym. We’ll also be deluged by diet and fitness advice. Sadly, tradition also dictates that you’ll ignore this. In Europe, there has been a serious decline in physical activity over the past 50 years. Adults aged 20-60 years expend 500kcal less energy per day than they did 50 years ago. As Dr Jules Pretty, professor of Environment and Society at the University of Essex, puts …