Regular physical activity is essential for the optimal function of many vital organs and tissues, and for general function. I am less sure about its direct and significant effects in the area of preventive medicine, but I can mention much indirect evidence to justify a whole-hearted promotion of physical exercise. Information about diet and exercise should be tied together. My present prescription for exercise is as follows: Daily -- at least 60 minutes of physical activity, not necessarily vigorous, nor all at the same time. During your daily routine, moving, walking, climbing stairs, etc., whether for one minute 60 times per day, 12 minutes 5 times a day, or any combination totalling 60 minutes, will burn up approximately 300 kcal (1.2MJ). Weekly -- at least two or three periods of 30 minutes of intermittent or sustained activity at submaximal rate of work (brisk walking, jogging, cycling, swimming, cross-country skiing, gymnastics etc.) are necessary for maintaining good cardiovascular fitness, and will consume an additional 750 kcal per week (3MJ).