The trends with increasing prevalence of overweight/obesity and sedentary lifestyle are alarming. The prevalence of obesity has increased markedly during the last 20 years in Europe and in USA; e.g. in USA, one quarter of Americans were overweight in 1978, one third in 1990 and in 2001 60 per cent of them had become overweight. The consequences of the stealthy epidemic has now been realised; the reasons lie in excess calorie intake and reduced physical activity. Maintaining a health body weight with the help of regular physical activity, and healthy diet, will reduce cancer risk. Overweight/obesity increases the risks for cancers of the oesophagus (adenocarcinoma), colon, breast, endometrium and kidney. Regular physical activity protects against cancers of the colon and breast.