This post may contain affiliate links. It costs you nothing and helps keep the lights on and weights racked here at Students Fitness. Read our affiliate disclosure if you're having trouble sleeping.
If your goal is to burn calories and lose weight, it doesn’t matter whether you eat before or after a workout.
Table of Contents
However, if your goal is to have the best workout possible, it’s recommended that you fuel yourself up so you can hit the weights hard and not end the workout early from fatigue.
While pre-workout supplements such as Mr. Hyde can help with that energy, caffeine doesn’t actually fill your muscles with glucose or prevent catabolism.
For that, you need protein and carbohydrates.
However, eating too much or too soon before a workout can be counterproductive.
So, how long should you wait after eating to workout? And why should you wait in the first place?
Why You Should Wait
The short of it is that if you eat and then immediately exercise, two things will happen.
The first is that you’ll feel sick, which will negatively impact your workout.
The second is that your body won’t be able to exercise as efficiently, which will destroy your gains.
Whether you’re seeking to put on muscle mass or burn off fat, effective workouts are far superior to failed or ineffective workouts.
You’re a busy person, why waste the time?
Let’s look at a few specifics.
Nausea and Cramping
Not everyone is as susceptible to this reason why you shouldn’t workout immediately after eating, but it’s relatively common.
Meals fill up your stomach and, if you mix that with physical activity, your stomach starts to revolt.
First, you’ll feel nauseated. I’d recommend stopping there. But, if you continue…
…your stomach will explode!
Wait, no, that’s just what my mother told me will happen if I swim too soon after eating. That’s not true, by the way.
In reality, you may start to feel cramps. If you’re lucky, it’ll stop there.
If not, that food may try to escape. It may leave either the front door or the back door, likely choosing the most embarrassing route for you at the time.
Vomiting or diarrhea will end your exercise routine real quick, so give yourself some time to workout after eating.
The second reason to wait after eating to workout is that you only have so much blood in your body.
Two of the activities which use the largest volume of blood are working out and digesting.
So, if you combine the two, your body won’t have enough blood to go around.
Your muscles won’t get the nutrients and fuel they need for the physical activity and they won’t be able to clear away waste lactic acid as quickly.
You know that pump you get when blood fills your muscles while working out, which makes you feel powerful and look good in the mirror? Yeah, you won’t get that.
This one is more specific to people who want to lose weight, but your body doesn’t burn as much fat if you workout with too much food in you.
Why would it? After all, you just gave it a bunch of calories.
However, some fuel is good. If you’re too depleted then your body will catabolize muscle for fuel, you won’t be able to exercise as hard, and so you won’t burn as many calories.
Food-Dependent Exercise-Induced Anaphylaxis
That’s a fancy term for having an allergic reaction to exercise after eating food.
Some people are allergic to certain foods, but the allergic reaction only occurs if that food is eaten within 3 to 4 hours of exercise.
It’s uncommon but still happens.
There’s even non-specific food-dependent exercise-induced anaphylaxis (nsFDEIA, which is fun to try to say), where any food before exercise triggers the allergic reaction.
If you feel swelling, have trouble breathing, become itchy, break out in hives, or have other allergy-style responses while exercising, you may have FDEIA.
Please, discuss it with a doctor.
So, now we know that you should wait a while before exercising. But how long should that be?
As it turns out, that depends on how much you eat.
Full meals require the most blood flow and time to digest, so you shouldn’t snarf down a five-course meal right before you pick up those dumbbells.
The recommended amount of time you should wait after eating a large meal is 3 to 4 hours. You may be able to squeak by with 2 hours if it wasn’t a large dinner.
You don’t have to wait nearly as long after a snack to workout. In fact, a pre-workout snack is often recommended.
Most of the time, you should eat protein and carbs for your pre-workout snack then should wait an hour or two.
If it’s especially light, such as a Quest bar, you can eat it half an hour before your workout. I wouldn’t chow on it as you walk into the gym, though!
I count protein powder shakes as snacks for this purpose, by the way.
Even pre-workout supplements shouldn’t be slammed seconds before you sprint.
However, they often don’t contain many calories. They’ll often just have a few grams of sugar, if they contain any.
Bucked Up, for example, contains no sugar.
You should still wait for 20 to 30 minutes before exercising, though.
They’ll digest fast but you still need to let them digest. Plus, it takes about that long for caffeine to start working.
No matter your fitness goals, you shouldn’t stack working out with eating.
Whether you’re lifting weights or running on the treadmill, eating too soon before exercise is counterproductive at best and can make you sick at worst.
So, time your endeavors properly. Fuel up then wait until you finish digesting before you exercise.
Your workouts will be better fueled and all of your blood will be able to go where it needs to go.