You just finished your workout. Your exercise is done and now you’re wondering if you should eat something or not. After all, you just burned a few hundred calories, surely you must be hungry. Plus, the cookie on the counter is calling for you. Or maybe it’s a Starbuck’s Frappuccino. Is this physiology or psychology? Is your exercise making you hungry or do you just think you are?
Hunger Hormones and Exercise
Your body has an intricate way of telling you if you’re hungry or not through several hormones regulating hunger. One in particular, ghrelin, is nicknamed the hunger hormone. It’s released when your stomach is empty and signals the brain to tell you to eat. When your stomach is full, it becomes stretched. This stretching of your stomach is the signal to stop ghrelin from being produced.
Another hormone, peptide YY, does pretty much the opposite. Release of peptide YY from the intestine reduces appetite. When we eat, peptide YY goes up and when we haven’t eaten for a while, peptide YY goes down.
Since exercise results in the burning of calories, you might expect ghrelin to go up and peptide YY to go down. But the opposite is more likely. Most studies indicate exercise reduces ghrelin and increases peptide YY. This has been linked to the exercisers feeling less hungry right after. It appears these hormone changes may be unique to exercise as reducing food intake (i.e. dieting) does the exact opposite resulting in increased appetite and higher food intake later on.
There’s a good reason your body doesn’t want you to eat immediately after exercise. When we eat, blood is diverted to the gut to metabolize the food and bring the energy and nutrients to where the body needs it. During exercise, however, blood goes to the working muscles. Along with the blood needed to keep the brain, heart, lungs, and other organs going, there’s little blood left for the gut. As a result, any food eaten would sit in your stomach undigested. So the body reduces appetite to prevent this from happening.
Of course, there may be times when one actually does feel hungry after exercise. This tends to occur after exercise of around two hours or more. By then, the energy stores in your muscles may have been used up and need replacing. However, most people exercise less than 30-60 minutes, so this isn’t an issue.
Not All Exercise Makes You Hungry
As with anything to do with the human body, it’s not as black and white as we’d like to think. There’s a complex connection between exercise, hunger and eating. Certain types of exercise may have a greater effect on whether you feel hungry than others.
For exercise to reduce appetite, it needs to be at high intensity (more than 70% of your maximum effort). When moderate and high intensity exercise were compared to no exercise, only the high intensity exercise reduced appetite. In some studies, but not all, high intensity exercise also reduced food intake immediately after.
The temperature in which you exercise can also affect appetite and food intake. Exercise in cold water, led people to eat more compared to exercise in warm water. This may be a response to the body’s core temperature going down, as eating is a way to boost metabolism and therefore increase body heat. Conversely, exercising in hot temperatures may suppress appetite as a result of changes in hormone signalling to the brain.
But it doesn’t always work that the hunger hormones dictate whether you feel hungry or not after exercise. In a study of people doing 45-minute exercise sessions, ghrelin decreased (suggesting a lower appetite), yet there was no difference in feelings of appetite compared to when the same people didn’t exercise on a different day. In addition, food intake didn’t differ between the exercise and non-exercise conditions. While exercise didn’t result in eating less, it clearly didn’t make people eat more.
Compensating Exercise with Food
Despite what our hormones may say, some people end up eating food as a result of exercise, often as a reward. I’ve been there many times. Having finished a big workout, I would grab my go-to reward, a cinnamon bun. I figured I needed the extra calories, right? Plus, I worked hard and deserved it.
This is referred to as compensation and has more to do with our thoughts than what our hormones are telling us. It’s common to think we need to eat in order to replace the energy just burned through exercise. The one problem is we usually overestimate how many calories we’ve used through exercise. That cinnamon bun I would eat was 440 calories and probably more calories than my workout.
There is also pre-compensation. This occurs when people eat more than usual in anticipation of an upcoming exercise session. A small study of 20 people reported those who exercised ate more in the meal directly before their session. While it was more food than those who didn’t exercise, the increased food intake was still less in calories than the exercise itself.
This may be disheartening for people trying to lose weight. But exercise isn’t great for weight loss. In part because it burns a lot less calories than one would think. And for those who compensate by eating more, this increase in food can counteract the calories burned from your exercise and lead to less weight loss than expected. That being said, exercise is far more than just burning calories and one’s weight isn’t how we should define our health.
The Bottom Line
This is all well and good, but if someone is exercising daily, surely appetite and food intake wouldn’t continually go down. Otherwise, we would waste away to nothing. Indeed, it seems that while appetite and food intake go down following exercise (or at least doesn’t go up), the days after exercise may result in a subtle and unconscious increase in intake to make up for it. Since most studies have only looked at the effects of food intake in the hours after exercise, they miss any changes that occur in the days after.
In the end, exercise doesn’t make you hungry, and in fact may do the opposite. Despite this, some people do increase their food intake, but this is more because they think they need to, not because their body is telling them to eat more.
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This post was originally published on July 10, 2019 and updated on July 20, 2022.