News Flash: Exercise burns calories. And while running off that breakfast burrito will probably spark an appetite in some, not everyone feels those hunger pangs after working out. So why do certain people clean out the fridge after an hour-long spin class, while others can’t seem to fit an apple in their stomach? Turns out a grumbling stomach depends on gender, body composition, and how intense that workout really was   .
Chew on This — The Need-to-Know
Hungry? Don’t grab a Snickers. According to recent research, more intense exercise sessions may decrease our appetite . Scientists put a group of overweight (but otherwise healthy) men in their 20s and 30s through different cycling workouts, while others just rested, and then measured how much everyone ate at a breakfast buffet. Turns out the men who rested or cycled at a moderate pace ate significantly more, at breakfast and even the next day, than the men who completed the most rigorous workouts. Those who went through the tough workout also had lower levels of the hormone ghrelin and higher levels of blood lactate and blood sugar, all of which are associated with a decreased appetite. Similarly, another study found that obese teenage boys ate less after an intense cycling session than after resting or exercising moderately .
And women, take note: Exercise can bring on the munchies more in females than in males, perhaps because women are wired to preserve body fat for childbirth  . So if hunger strikes, try not to overestimate calories burned. One Krispy Kreme may easily negate what’s burned during an afternoon jog in the park.
As for hormones, they’re not just the topic of middle school sex ed. Scientists have found obese women are hungrier after exercise because of a resistance to leptin, a hormone that keeps energy balance in check and may help suppress appetite. And for individuals at a healthy weight, aerobic and anaerobic exercise may suppress appetite by altering the hormones ghrelin and peptide YY . Another study found short-term exercise had no effect on ghrelin, so perhaps the 4-minute Tabata won’t make those French fries look less appealing (if cutting calories is the goal) .
Fast(ing?) Food — Your Action Plan
That appetite may rise or fall, depending on body composition and what’s on the fitness agenda. For those who don’t feel hungry after working out, it’ll probably be short-lived. Intense exercise may make it feel like the stomach is shrinking, but the desire for food will reappear soon after (though it’s unclear exactly when) . Just remember, it’s important to re-fuel post-workout to keep energy levels up and repair muscles no matter what the stomach is saying. Pro tip: Sneak in some protein within two hours of working out to keep the body running in top-top shape.
And for the champs who feel super-starved immediately after exercise, make sure to drink plenty of water and have a small snack before exercise to avoid overeating post-workout. Also note it may all be in the mind, so really tune into those hunger cues! (Is the stomach really growling, or is it just the munchies talking?) Some scientists suggest diving headfirst into a bag of chips may simply be an act of self-reward after all those supersets . So if weight loss is the goal, find some inedible rewards instead. A massage can definitely be way more satisfying than this pizza pie.
This article originally posted May 2012. Updated September 2013.
What’s your post-workout M.O? Tell us in the comments below!