Did your mom ever tell you that it’s dangerous to swim after you’ve eaten? Apparently, that cake, burger, and fries would divert blood away from your muscles and keep it occupied in your digestive system instead, resulting in agonizing cramps so terrible you could drown.
Is this advice valid or more of a myth? Is exercise after eating good or bad for you? Even when you look at the research, it’s a hotly debated question with no definite answer.
Should you eat before working out?
It depends on the food you eat, the type of exercise you’re planning to do, and how much time passes between eating and exercising.
If a short, gentle workout is the order of the day, then eating beforehand isn’t necessary to fuel your efforts. But if you’re feeling peckish, eating shouldn’t have any major side effects.
If you’re aiming to burn fat, it may be helpful to exercise in a fasted state. But in the long term, the fat-burning benefits might fall flat.
If you’re prepping for endurance exercise, then eating beforehand could improve your performance — but it could also give you an upset stomach.
To minimize tummy issues, it’s wise to wait 1 to 2 hours after a meal and 30 minutes after a snack before exercising.
So, what’s the deal? When thinking about exercise, keep in mind that there’s a vast difference between a gentle walk and a triathlon. Likewise, with food, there’s a stark contrast between a granola bar and a three-course meal.
We explored whether it’s safe to exercise after eating.
It’s not quite that simple
There’s no cut-and-dried answer since both eating and exercise take place along a spectrum.
First, consider the time frame. Are we talking about exercising right after eating? An hour after eating? Or longer?
Then there’s the fact that snacking on an apple and cramming in Thanksgiving dinner are two sides of the eating coin. Likewise, a gentle stroll around the park and a triathlon are both considered exercise.
In short, multiple variables are at work here.
Food and exercise are significant contributors to your health, along with genetics, environment, and lifestyle. But the relationship between the two is somewhat complex.
You need nutrient-rich food to fuel your activity and to repair your tissues after working out. On the other hand, the way your body moves can affect your digestion by stimulating your gut and increasing intestinal activity.
The question of whether working out after eating is a good idea doesn’t have a definite answer because it depends on your goals. Maybe you’re trying to lose body fat, or perhaps you’re an athlete relying on food for fuel.
It might make you feel sick
Some people feel sick and sluggish if they work out right after eating. Exercise-induced vomiting is real, friends.
Higher blood sugar might help super athletes… but fasted exercise could burn more fat
For some, working out after eating is a great idea.
It probably comes as no surprise that your blood sugar is higher if you eat before you exercise. A 2018 review compared fasted versus fed exercise and found that people who ate before exercising had elevated blood sugar, which could be ideal for serious athletes.
Fasted exercise increased the amount of post-exercise circulating free fatty acids (FFAs), resulting from the breakdown of fat cells. In other words, training on an empty stomach means you burn more body fat.
If your goal is to lose body fat, you may think the best plan is not to eat before exercise. But hold your horses — it’s not so clear-cut.
While some research suggests that exercising in a fasted state has possible benefits, there’s no concrete evidence that it helps with fat loss.
In a small 2013 study, researchers divided 16 women in the overweight BMI category into two groups. Both groups took part in 18 high-intensity interval training workouts over 6 weeks, but one group worked out in a fed state and the other in a fasted state.
The researchers found no significant difference in body composition, muscle oxidative capacity, and blood sugar control between the two groups.
Carb loading *might* boost performance in longer exercise
And what about performance? That’s also something to think about.
You’ve probably heard the term “carb loading,” meaning stuffing your face with delicious carbohydrates to give your body enough fuel for serious exercise prowess. (In other words, eating before working out.) But is it necessary?
Once again, the science is as tangled as a drunk spider’s web. It also depends on what you mean by exercise.
If you look at weight training, there’s not a lot of info out there. Some research from 2013 suggests that whether you eat before or after a workout doesn’t make much difference in your ability to carve those swole muscles.
Similarly, researchers in a 2018 review didn’t find a relationship between eating and performance during short-duration aerobic exercise of less than an hour.
However, the review did find that a pre-exercise carb load could enhance results when the exercise lasted longer. So, if you’re planning a 30-mile run, eating beforehand might be a good idea.
So… WTF is going on?
OK, breathe. We’ve got you.
Overall, it seems that if you’re planning a short, gentle workout, then eating beforehand shouldn’t have any puke-based side effects, but it’s also not likely to boost your performance.
If you want to burn fat, exercising without eating first seems like the best plan — but the benefits might not continue in the long term.
For endurance-minded folks whose idea of exercise is more along the lines of a marathon, eating before exercising (or even midrun) could help increase stamina but may also increase the risk of digestive upset.
It’s a good idea to wait a couple of hours after eating before you work out. It takes 2 to 3 hours for your stomach to empty the food into your small intestine.
Although complete digestion takes much longer, 1 to 2 hours after a meal and 30 minutes after a snack is long enough for most people to feel comfortable and avoid any digestive issues. But again, it’s not quite as easy as “this is exactly how long to wait.”
What you eat and the intensity of your planned activity affect the wait time. If you jam in a giant meal, it’ll take longer to digest, meaning you should wait longer before exercising.
Plus, you need to think about what you’re eating, not just the amount. Your body digests nutrients at different rates. A meal high in fat, fiber, and animal protein will typically break down more slowly than a carb-rich meal.
But everyone’s digestion is different. The best plan is to listen to your body, see how you feel, and do what works for you. Some people are comfortable exercising right after eating, but you may need to wait a few hours before you’re good to go.
As a rule, if you’re planning gentle exercise like walking, you’re probably OK to do it directly after eating. But if CrossFit is more your thing, you might want to hit pause until 3 hours after your meal.
There haven’t been any studies comparing the safety of different kinds of exercise after eating.
But generally, the more intense the exercise is, the more likely you’ll be to experience uncomfortable side effects after eating. Odds are that doing 50 burpees will make you feel extremely burpy. Or nauseated. Or worse.
If your only available time for exercise is directly after eating, you should probably stick to something gentle like yoga (without headstands), walking, or golf. Maybe now is the time to take up archery or competitive rain boot throwing.
For some people, weightlifting is a safe activity after eating. If weights are your thing, you can give them a go and see how it works for you. It’s best to start small and work your way up, because there are no firm rules and everything depends on your metabolism, biology, and exercise routine.
If you plan to do any exercise that makes you extremely out of breath or bounces your stomach around, you should probably leave it until a few hours after you’ve eaten.
Although the evidence is somewhat rocky, eating the right thing, rather than just any old thing, could help boost the caliber of your workout while minimizing muscle damage.
It’s important to prioritize two nutrients. You’ll need some good ol’ carbs, because they are your body’s primary source of energy. And some protein will help with tissue repair, because building muscle is hard work and you need to maintain that mass.
With that in mind, here are some examples of protein- and carb-filled snacks:
- a banana with a tablespoon of peanut butter
- a piece of whole-grain toast with a hard-boiled egg
- a portion of nonfat Greek yogurt with fruit
- a handful of nuts and raisins
- a fruit smoothie with a dash of protein powder
- a scrambled egg with avocado
- a small portion of oatmeal mixed with protein powder and blueberries
How much to eat before a workout
If you’ve got big athletic ambitions, think in terms of smaller snacks. If you’re only leaving yourself 30 minutes before you work out, make sure not to eat anything too large that sits heavily in your stomach.
Your stomach isn’t that big, despite what the fourth slice of pizza tells you. Its capacity depends on your size and weight, but a typical stomach measures just 13 centimeters wide, 15 centimeters thick, and 10 centimeters high, and it can hold around 1 quart.
Think about this when you choose your pre-workout snack, and try to choose something that’s nutrient-dense but smaller than your fist.
Not everyone experiences negative effects from eating before a workout. But everyone is different, and you should be aware of the potential for digestive symptoms and less-than-stellar performance if you eat before you exercise.
Studies indicate that 30–50 percent of athletes experience issues like bloating, nausea, vomiting, and diarrhea. Cramping and sluggishness are also possible and can affect performance.
Endurance runners are particularly at risk — up to 90 percent experience exercise-related digestive problems. Cyclists are also at particular risk of gut issues because of their position, which increases pressure on the abdomen.
What you eat could be as important as when you eat.
A small 2014 study with 10 male participants noted that eating a carb- and protein-rich meal before playing basketball caused gastrointestinal side effects, but the presence of protein reduced muscle damage. Side effects weren’t as prevalent in men who ate a high-carb meal with no protein.
So even though experts typically recommend eating protein and carbs before you work out, you should experiment and see which nutrient combo suits you best.
To eat or not to eat before exercising: That is the question. And there doesn’t appear to be a one-size-fits-all answer. If you exercise without eating, it could increase the amount of fat your body burns as fuel, but overall, it might not drive a significant loss of body fat.
There isn’t much evidence that eating before short-duration exercise makes a significant difference in performance. But if you’re planning a that’ll drain your energy stores, eating might be beneficial.
To avoid or minimize side effects, plan on waiting 1 to 2 hours after a meal or at least 30 minutes after a snack.
The primary takeaway is that everyone’s different, and you should listen to your body to find out what suits you.
If you’re feeling weak and tired during a workout, maybe a snack could boost your energy. Or, if pre-workout food makes you feel sick, you should leave more time between eating and exercising. You may also want to consider which nutrients you’re consuming and cut down on protein and fiber.