20 Mins of Exercise a Week Keeps Shrink at Bay Far less clear is how much exercise is best for physical health By Jane Yager, Newser Staff Posted Dec 30, 2009 11:25 AM CST 2 comments Comments The mental benefits of jogging are clearer than the physical benefits. (Shutter Stock.) (Newser) – If the goal of your exercise program is better mental health, a new study shows that even 20 minutes a week of sports, gardening, or housecleaning may be enough to boost your mood. But if you want to improve your cardiovascular fitness, lose weight, or reduce your risk of life-threatening diseases, figuring out the best amount of exercise becomes much trickier, the New York Times reports. Recent sport science on the health benefits of exercise is wildly inconsistent: Some studies say exercise in any dose has little effect on risk of disease, depression, and premature death; others say only very rigorous exercise helps; others say even a walk a few times a week reduces the risk of early death. But what scientists do agree on is that the biggest difference is between no exercise and a little exercise: Moderate activity benefits the sedentary more than a stepped-up workout benefits the athletic.