Experts generally agree that thirty minutes a day of moderate physical activity is enough to help prevent diabetes, high cholesterol, and high blood pressure among other conditions. While some people like to think that a two-hour run makes them four times as healthy, it doesn’t work that way with excessive exercise actually having the opposite effect. Working out too much can lead to boredom, injury, and even exercise addiction, with extreme fitness routines often attracting people who feel an intense need for control in their lives.  

According to a new study from Denmark published in the Journal of the American College of Cardiology, less exercise really is more. In the study, more than 1000 regular exercisers and nearly 4000 healthy, sedentary people were followed over a 12-year period. While light joggers who exercised two to three times a week for between one and 2.4 hours had the lowest risk of dying, moderate and extreme runners who worked out two to three times a week for up to or more than four hours a week had a slightly higher risk of death than healthy sedentary people.

Associate Professor David Dunstan, head of the Physical Activity Laboratory at Baker IDI Heart and Diabetes Institute, says the study confirms an important point often forgotten by exercise enthusiasts: "The key message is that doing something is better than doing nothing," but "if you're doing a hell of a lot of exercise you may be predisposing yourself to increased risk." According to Jacob Marott, a researcher at the Copenhagen City Heart Study at Frederiksberg Hospital and one of the study's co-authors, "If you want to do something good for yourself, you don't have to be extreme ... Jogging one to four hours a week for no more than three days a week at a slow to moderate pace is actually achievable. And that's a positive take-home message."

If you do feel the need to exercise at a higher level of intensity, extra hours at the gym are not necessarily the answer. While moderate exercise over a long time period does have its place, nothing can ignite your metabolism like periods of high intensity exercise. Sequences of intense activity with rest periods in between burn calories faster than continuous exercise and work more muscle groups in less time. Instead of thinking about how many hours you spend working out, its important to make the most of the time you do have available.