Running hot and cold on exercise and weight loss


It’s that time of year again.

Our news world is full of new year’s resolutions and science reporting on exercise and weight loss. The latest trend seems to be running while cold. The theory is that our overheated houses are contributing to weight gain and that we burn more calories when we have to work to maintain our body temperature.

Basic idea: Warmth is making us fat and running with an ice vest on can help fix that

See The Health Benefits of Cold.

Cronise began a regimen of cold showers and shirtless walks in winter, and he lost 26.7 pounds in six weeks. He began measuring his metabolism during and after cold exposure, and found that his body was burning a tremendous amount of energy. Rather than storing energy as fat, his body was using it to sustain his core temperature. Cronise’s preliminary experiments led him to put together what is now a pretty high-tech lab in his Huntsville, Alabama, home, where he conducts miniature scientific studies, mostly on himself. All of this attracted publicity, naturally. Timothy Ferriss hyped Cronise’s unorthodox weight-loss success in the 2010 best seller The 4-Hour Body. That same year, Cronise gave a popular TEDMED Talk. Wired ran a feature story describing his home laboratory, titled “The Shiver System.” Through it all, Cronise endured not just the obvious physical discomfort of his endeavors, but the discomfort of personal and public criticism. Some detractors raised concerns about regularly exposing one’s skin to cold (Cronise shared these worries); others accused him of diverting people away from solid principles of weight management and toward dubious shortcuts.

But not so fast….other research shows that people who run in warm environments lose more weight.

Exercise to lose weight? Stay warm, says the New York Times’ Gretchen Reynolds.

The researchers conclude, warm temperatures demand more from the body, because it must dissipate any buildup of internal heat. Blood flows away from the stomach and limbs and toward the skin surface so that the excess heat can be released.

When you exercise in cooler conditions, said Daniel Crabtree, a research fellow at the University of Aberdeen, who led the study, “you don’t have to pump blood to the surface to dissipate heat.” The blood instead circulates normally, picking up and distributing biochemical signals from the stomach and elsewhere that apparently prompt the release of ghrelin, augmenting appetite and undercutting your best intentions to forgo that cupcake after exercise.

What to think? It’s not clear. Researchers seem to go back and forth on this one every year. We’ve even blogged about it before. See Does heat make you fat? No wait, it’s cold.

Our advice: Focus on fitness. Warm or cold, just run. Do what feels good. You’ll do more of it. Me, I’m skipping the ice vests.

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