View Related Gallery »ThinkStock
GalleryPaul Asman and Jill Lenoble, Wikimedia Commons
D-Kuru, Wikimedia Commons
Scott Bauer, USDA, Wikimedia Commons
Harald Bischoff, Wikimedia Commons
José Manuel López Pinto, Wikimedia Commons
Peter Gugerell, Wikimedia Commons
Peter Bagi/Corbis
Per-Anders Pettersson/Corbis
Vincent van Gogh/Wikimedia Commons
Luca Galuzzi, Wikimedia Commons/www.galuzzi.it
Although exercise and fasting can produce some similar results (increased production of BDNF, for example), Eric Ravussin, Associate Executive Director for Clinical Science at the Pennington Biomedical Research Center, points out that the mechanisms are very different. Still, there's some preliminary ruminating that combining a short fast and exercise could piggyback to more quickly get the optimal results.
"The thing that's important is to dig into fat stores," Ravussin said. "The longer the fast,the better. Or the more exercise, the better. If you could run at 6 a.m. and then skip breakfast, this would be the ideal."
"We haven't connected all the dots, but we know that exercise and intermittent fasting increases BDNF and that BDNF can slow resting heart rate," Mattson said.
In a review published this week in PNAS, the authors (including Ravussin and Matson) point out that an intermittent fasting type of diet has evolutionary roots -- it's likely closer to the way our ancestors ate.
But if the thought of fasting makes you cringe, there's good news: intermittent fasting can be as simple as severely restricting your calories just two days a week. Eat what you want five days of the week, and then eat 500 or so calories twice a week. Most people have better success at that model, which is popular in some fitness circles, than its precursor, alternate day fasting.
"It's tough for most people," said Ravussin, referring to alternate day fasting. "My wife told me never to do it again."
