To get the most health benefits from exercise, don’t become an extreme endurance runner.

That’s the gist of several new studies showing that while daily exercise is important for good health, too much exercise can be bad for us. And experts say endurance running, in particular, is dangerous. Because while running every week is a proven way to add up to six years to our life, a new study says that running more than 30 miles a week increases our risk for heart disease – and an early death. Or, to put that another way: Researchers say extreme endurance running is the exercise equivalent of smoking, or eating a cheeseburger.

I know that goes against the image of “perfect health” that a lot of Ironman athletes and marathon runners have. But it turns out, there are many cases of endurance runners being forced into retirement because of heart conditions you’d expect to find in people who eat high-fat diets – which are instead linked to over-exercising.

So why is “over-exercising” so dangerous? Dr. John Mandrola is a cardiologist who says heart disease comes from inflammation…And when you’re constantly exercising - by running the equivalent of a marathon every week, for example – it means you’re chronically “inflaming yourself,” because you’re never giving your body time to heal.

The key is to find the right balance between no exercise and too much. That’s why Dr. Mandrola now recommend short intervals of high intensity exercise – like running on a treadmill as fast as you can for just 5 or 10 minutes. Believe it or not, Dr. Mandrola says that’ll do more to boost your health than running marathons.