A vigorous sixty-minute workout affects the release of two key appetite hormones, ghrelin and peptide YY. Ninety minutes of weight lifting, however, affects only the level of only ghrelin.
The research shows that aerobic exercise is better at suppressing appetite than non-aerobic exercise, and provides a possible explanation for how that happens.
Ghrelin is the only hormone known to stimulate appetite, while peptide YY suppresses appetite. In an experiment, 11 university students took part in three eight-hour sessions. During one session they ran for 60 minutes on a treadmill, and then rested for seven hours. During another they did 90 minutes of weight lifting, and then rested for six hours and 30 minutes. During another session, the participants did not exercise at all. The researchers measured ghrelin and peptide YY levels at multiple points along the way.
They found that the aerobic treadmill exercise caused ghrelin levels to drop and peptide YY levels to increase, indicating the hormones were suppressing appetite. However, a non-aerobic weight-lifting session produced a mixed result. Ghrelin levels dropped, indicating some appetite suppression, but peptide YY levels did not change significantly.