In the first part of the study, 11 college men were asked to run on a treadmill for 60 minutes and then rest for seven hours. In the next segment, they lifted weights for 90 minutes and then rested for six and a half hours. In the final segment, participants did not exercise at all. In all three sessions, subjects were asked to rate their hunger levels at certain intervals; their ghrelin and peptide YY levels were measured at various times throughout the study.
Participants rated their hunger as suppressed after both exercise sessions, but it was rated as more suppressed after aerobic exercise.
The researchers found that after the aerobic workout (treadmill running), ghrelin levels were lower and peptide YY levels were higher than before the workout, suggesting that appetite was suppressed. After weightlifting, only ghrelin levels were lower. How did these changes correspond to the participants' ratings of their hunger levels? Fairly well: participants rated their hunger as suppressed after both exercise sessions, but it was rated as more suppressed after aerobic exercise.
Including the time participants spent exercising, the changes in hormone levels and hunger ratings only lasted for about two hours.
Researcher David L. Stensel says that the result that "hunger is suppressed during and immediately after vigorous treadmill running is consistent with previous studies indicating that strenuous aerobic exercise transiently suppresses appetite. The findings suggest a similar, although slightly attenuated response, for weight lifting exercise."
The team says that future studies will focus on whether or not exercise also affects how much individuals actually eat after exercising, since, as many of us know, hunger and food consumption are not always perfectly correlated.
The study was conducted by researchers at Loughborough University in the United Kingdom.