After that, experts and observers have different views. One of the problems with many studies is that the people in the study are not always chosen randomly. A recent large study gave some answers, and raised other questions.
The study looked at thousands of runners and walkers. It found that, over six years, the runners maintained their weight. Although the walkers used up as many calories as the runners by walking for long periods of time over long distances, they put on weight.
Observers noted that the runners were thinner at the start of the study.
Another study suggested a different reason for the different outcomes. Runners and walkers ran or walked on a treadmill for an hour. Then they ate at a buffet. The next day they did not run or walk. They again ate at a buffet. The walkers had bigger appetites than the runners. The walkers consumed 50 calories more than they did after walking. The runners consumed 200 calories fewer than they did after running.
Researchers said the runners had much higher levels of a hormone called peptide YY. This hormone is known to reduce appetite. So to eat less… run more.
Walking also has benefits. Another study looked at walkers and runners who used the same amount of energy. Walkers reduced their risk of heart disease by more than 9 percent. Runners reduced their risk of heart disease by about 4.5 percent. Of course the walkers had to walk longer than the runners had to run in order to use the same amount of energy.
A last note on eating. The appetite study had people just sit for an hour and then eat. Runners and walkers both consumed 300 more calories than they did while sitting. Any exercise makes a difference.