Many studies have suggested that regular physical activity, including walking for just 30 minutes a day at a moderate pace, may improve health.
But new research says it's the intensity rather than the duration that makes the difference.
The study in BMJ Open found fast walking, jogging and other forms of more vigorous exercise may slash your risk for heart disease and diabetes.
Specifically, fast walkers and joggers who exercised for two to four hours per week were up to 50 percent less likely to develop what's called metabolic syndrome.
Participants who walked at a casual pace for about an hour a day made no difference in their risk to develop the syndrome.
Experts say you have to sweat for it to count.
But not everyone agrees. Some experts argue that moving in any amount is healthful.