Those who are still running outside this season understand that exercising in the cold is difficult. With every inhale, the air bites cruelly at your throat and lungs. You likely assume that, because the body must also heat itself, you expend more energy working out in the cold. Surprisingly, however, a new study not only found that warm temperatures demand more from the body, but also makes people less hungry after a workout.
Researchers recruited overweight, sedentary men and women, a group of people that typically have the greatest difficulty losing weight using exercise alone. First, they measured the volunteers' resting metabolic rate, maximum endurance capacity, and blood levels of appetite-related hormones.
They then had each participant walk on a treadmill at a pace that represented about 60% of each person's maximum aerobic capacity for 45 minutes. They did these walking sessions twice and wore the same clothing each time. The first time, the thermostat of the room was set to 68 degrees. And the second time, the room's temperature was lowered to 46 degrees. Humidity stayed at a consistent 40%.
During each workout, the researcher's tracked the participants' inner and outer body temperatures, measured how much energy they were expending, and periodically asked them how warm or cold they felt.
At the end of each session, the volunteers rested for 45 minutes while their blood was being drawn and then told they could help themselves to a large food buffet afterwards — but they weren't told their portions were being monitored.
The researchers took note of how many calories and what types of foods each volunteer ate after each exercise session.
After comparing all the data they collected, the scientists found that almost all of the walkers consumed significantly more calories and more carbohydrates after they had been walking in the cold.
Most of the blood drawn from people after exercising in the cold also showed higher blood levels of a hormone called ghrelin that is known to induce hunger, while there was little change in ghrelin levels after the warmer exercise.
In general, the researchers found that the volunteers were much more hungry after working out in the cold, dumping much more food on their plates than when they had been warm during their workout. And their workout had not warranted this type of hunger — they had spent significantly fewer calories working out in the cold versus the warmer temperature.
However, it's important to note that this experiment was both small and short term. Since it only involved a very particular type of person, we can't say whether younger, thinner or more active people's bodies would respond similarly, said Dr. Crabtree, the lead author. Follow-up research needs to be done to determine how age, body type, exercise intensity, and extreme temperatures affects appetite.
But this study does have some compelling evidence, though it may be too late to help you hold back from all the holiday feasting. It's something to keep in mind when if and when you decide to work off Grandma's goodies. Start piling on the layers in order to stay warm and shed the built-in, unwanted ones.
(h/t The New York Times)