However, new research shows that not all exercise is created equal when it comes to appetite suppression. The study showed that 60 minutes of vigorous aerobic exercise releases both of these key hormones while 90 minutes of weight training releases only ghrelin.
Peptide YY, discovered in the early 80s, is an appetite suppressant while gherlin, discovered by Japanese researchers in the late 90s, is an appetite stimulant. Gherlin was first identified for its role as a growth hormone and it was not until later that its effect on stimulating appetite was known.
Participants in the study, 11 healthy male university students, underwent three 8-hour trials. In the first trial, they underwent 90 minutes of free-weight training followed by a 6.5 hour rest period. In the second trial, they were made to run 60 minutes on a treadmill followed by 7 hours of rest. In the last trial, they rested for 8 hours. The trials used a randomised crossover pattern. Meals were provided twice each session. Throughout the trial hunger levels, measured by having the students fill out surveys, and plasma concentrations of ghrelin and PYY were monitored.
The study registered significant correlation between hunger levels and the ghrelin and PYY hormones with increased PYY levels and suppressed appetite after aerobic exercise.
Despite the fact that they were able to show changes in ghrelin and PYY due to exercise, the study stated that “further research is required to establish whether exercise-induced changes in ghrelin and PYY influence subsequent food intake.”
Body weight can also significantly affect the role that aerobic exercise plays in appetite suppression. A similar study, also using treadmills but employing significantly less energetic sessions, measured the appetite levels of obese women versus lean women following aerobic exercise. It found that obese women reported no appetite suppression due to the exercise.
Katarina Borer, PhD, lead author of this study concluded “obesity interferes with leptin's detection of exercise energy expenditure and with appetite suppression. Obese women perhaps need to consciously watch their calories because some of the hormonal satiety [fullness] signals don't seem to work as well.”
The hormones ghrelin, PYY, and leptin all play important roles in influencing appetite and they themselves are affected by the type of exercise engaged in and by the body’s fat content.
