Narrator: This is Science Today. The Centers for Disease Control and Prevention recently reported obesity is fast becoming a national epidemic. While the report did not delve into the reason, it suggests the most likely cause is lack of exercise. Ronald Krauss, a senior scientist at the Lawrence Berkeley National Laboratory and member of the American Heart Association's Nutrition Committee, says while there's not a total consensus on the what the best exercise regimen should be, it's clear the nation is not doing enough.

Krauss: If we want to eat as much as we're eating, we're going to have to exercise more. If we don't exercise more, we're going to have to eat less. There's no two ways about it. That's the only way to deal with the obesity epidemic that we're now facing.

Narrator: Krauss stresses some exercise is better than none at all.

Krauss: While we want to encourage at least minimal physical activity in the population as a whole and certainly to balance what we're consuming in terms of calories, we also think that people should recognize that they could do more. The more physical exercise you can build into your life, the more steps you can take - literally - to get out of your chair and move, the healthier you're gonna be.

Narrator: For Science Today, I'm Larissa Branin.