For the past year, I have been trying to run at least a few times per week. I've always been interested in the fact that I'm not very hungry after a run or a game of basketball. In fact, not only am I not hungry, but I usually want nothing to do with food for period of time (probably around an hour). I always thought this was some personal trait, likely connected with my experience as a high school wrestler and the necessity to avoid food after a workout in order to make weight.
However, I was pleased to see the New York Times detail a small study that explains the science behind this feeling and that it's fairly common. For others who also have wondered why they're not hungry after a run, I've put the relevant part of the article below; the study is comparing the post-workout appetites of runners and walkers. It's pretty interesting!
The walkers turned out to be hungry, consuming about 50 calories more than they had burned during their hourlong treadmill stroll.
The runners, on the other hand, picked at their food, taking in almost 200 calories less than they had burned while running.
The runners also proved after exercise to have significantly higher blood levels of a hormone called peptide YY, which has been shown to suppress appetite. The walkers did not have increased peptide YY levels; their appetites remained hearty.
So, this study shows that running triggers a hormone known to suppress appetite. Maybe the body is in a kind of lock-down mode due to the running and trying to focus on the task at hand or it is afraid of getting disturbed and hurting performance if it ingests food? A scientist I am not, but I can certainly imagine some reasons this would happen while your body is under the stress of quickly burning energy.
I encourage you to read the full post on The Times' Well Blog, as it looks at why runners seem to remain thinner throughout their lives compared to walkers who burn a similar amount of calories in their exercise routines. For me, it was cool to discover that I'm not alone and there is a scientific reason for having less appetite after a run.