The Real Reason Working Out Makes You Hungry
Being hungry post-workout seems reasonable. After all, you just worked hard and burned some calories, so naturally you'd be ravenous. As it turns out though, there's more to the story.
Hunger isn't caused by calorie burn alone: The sensation of hunger is triggered by the hormone ghrelin, which doesn't get released just because you've put in a strenuous session at the gym. Rather, it's linked to your blood sugar, and keeping it stable. So if you're starving during or immediately post-workout, that likely means that you entered your workout under-fueled, and your blood sugar has dropped. "As long as your blood sugar is at a good level, just burning calories alone doesn't necessarily mean your body is going to create a hunger response," exercise physiologist Heather Milton explained to SELF.
Your body uses muscle glycogen in order to fuel your workouts, and as you use up those stores, your blood sugar drops in order to remind your brain that it's time to eat and refill. If you've snacked before a workout, and you're eating during longer or harder sessions, the ghrelin hormone should stay stable. But if you skip a snack, your body will remind you that it's time to refuel (via SELF).
If I'm eating enough, why am I hungry?
Surprisingly, you may not actually be hungry: Sometimes, dehydration can feel a lot like hunger. "Mild dehydration is often masked as feelings of hunger, when really your body just needs fluids," dietitian Alissa Rumsey told Health. Make sure that you drink enough before, during, and after exercise so that you don't end up with the munchies afterwards.
It could also be that you haven't eaten enough carbohydrates or protein throughout the day. Your body largely depends on carbohydrates to fuel workouts, but protein also has an important role in the process. If you've skimped on either of these macronutrients, you may find that you're more ravenous than usual. Check how you've been fueling throughout the day, and you may notice certain patterns emerging, like being hungry after your bootcamp class on the days you skipped the chicken breast (protein) on your salad at lunch (via the American Council on Exercise).
If you're exercising later in the day, you could simply be falling victim to the rise in hunger hormones that tends to come later in the day. Consider swapping your workout to an earlier time block, or planning ahead with a healthy post-workout snack at the ready.