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How does intermittent fasting affect your health? By intermittent fasting, we mean people who fast part of the time. Some skip one meal a day; some don't eat at all for several days per week. NPR's Allison Aubrey reports on a study that tracked what happens when people go hungry for 14 hours per day.
ALLISON AUBREY, BYLINE: There are lots of trendy ways to fast. Some people skip multiple meals. Some fast a few days a week. But Pam Taub, a cardiologist at UC San Diego, says there hasn't been a lot of evidence on which strategies are effective.
PAM TAUB: There's a lot of bogus claims out there.
AUBREY: People touting extreme versions, such as two-day fasts, which can be dangerous. Taub and her collaborators decided to test a simple and much more moderate approach. They asked people to restrict their eating to a 10-hour window each day.
TAUB: We didn't ask them to change what they ate. We didn't ask them to change the number of calories that they consumed.
AUBREY: The only instruction was to stick to the 10 hours. So if they ate breakfast at 8 a.m., their last bite of food for the day would need to be eaten by 6:00 p.m., making for a pretty early dinner. The participants followed this diet for three months, and Taub says she really didn't expect the results she found.
TAUB: We saw a 3% reduction in their weight and a 4% reduction in the abdominal visceral fat. So it is surprising to get these types of results.
AUBREY: Especially since all the participants really did was to stop eating a few extra hours each day. It turns out that by shutting off eating early, the participants, all of whom were overweight and at risk of diabetes, ate about 8% fewer calories. But this alone, Taub says, is unlikely to explain the weight loss. She thinks there may be other factors at play.
TAUB: So when you go into a fasting state, typically over 10 hours of fasting, you start to deplete the glucose stores in your body and you start to use fat as your energy source.
AUBREY: In other words, rather than fueling your body on stored sugars, you begin to fuel your body with stored fat. This study was small. Taub and her collaborators have a larger NIH-funded study underway. For now, the new findings offer some preliminary evidence that a 14-hour fast can be beneficial.
TAUB: When you're constantly giving the body calories, you're constantly making your cells work.
AUBREY: Taub says, think of a few extra hours of fasting as a way of giving your metabolic organs some rest.
Allison Aubrey, NPR News.
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