Before, during and for three hours afterward, the researchers drew blood to check for changes in hormones related to appetite and asked people how hungry they felt. They also let everyone help themselves to an open buffet lunch of lasagna, salad, rolls, soda and poundcake with strawberries, while unobtrusively monitoring how much food people consumed.
Then the researchers compared hormones, hunger and actual eating and found odd disconnects. In general, people’s hormones shifted after each exercise session in ways that could be expected to reduce their appetites. But the study’s participants did not report feeling less hungry — nor did they report feeling hungrier — after their workouts compared with when they had sat. And at lunch, they ate about the same amount, about 950 calories worth of lasagna and the other buffet foods, whether they worked out or not.
The upshot of these results suggests that, at the very least, brisk walking or light weight lifting may not affect our subsequent eating as much as “other factors,” such as the aroma and oozing gustatory delights of lasagna (or buttery rolls or pie), said Tanya Halliday, an assistant professor of health and kinesiology at the University of Utah, who led the new study. People’s appetite hormones may have dropped a bit after their workouts, but those drops did not have much effect on how much they ate afterward.
Still, exercise burned some calories, she said — about 300 or so each session. That was less than the nearly 1,000 calories the volunteers consumed on average at lunch, but hundreds more than when they sat. Over time, this difference might help with weight control, she said.
Of course, the study has obvious limitations. It looked at a single session of moderate, brief exercise by a couple dozen out-of-shape participants. People who work out regularly, or who do more strenuous workouts, might respond differently. Researchers will need to conduct more studies, including those with more diverse groups and those that take place over a longer time period.
But even now, the findings have a gentle, apple-pie allure. They suggest “people shouldn’t be afraid that if they exercise, they will overeat,” Dr. Halliday said. And, she said, “Thanksgiving is just one day” and will not affect your weight in the long term. So, eat what you want at the feast and enjoy. Dr. Halliday also recommended going for a walk or join a Turkey Trot with your family and friends beforehand, if you can — not to blunt your appetite, but to boost your social bonds and to be thankful to be moving forward together.