We don’t always have the luxury to choose when we work out. If you have a busy schedule, you might fit a quick workout in during lunch, assuming you’re lucky enough to have a full lunch hour – or it might come down to grabbing a quick lunch and grabbing the weights for 30 or 40-minute session. Life is hectic and you don’t always have the luxury of waiting two hours to exercise after eating. So, if you have to hit the weights or do cardio is it okay to exercise after eating, is it harmful?
Is It Okay to Exercise After Eating?
On the plus side, if you chow down on a meal before working out, your body isn’t deprived of fuel, but it’s a bit deceiving. That’s because the amount of glycogen in your muscles is more dependent on what you’ve eaten in the past 12 hours, not the meal or snack you grab 15 minutes before a workout. Eating a meal just before a workout, if you haven’t been skimping on food intake for the past 12 hours, isn’t enough to optimize your glycogen stores. So, a fast meal on the fly won’t make up for 12 or more hours of eating too little.
So why do you often hear that you shouldn’t exercise after eating? One downside to eating a meal or large snack before a workout is it can trigger digestive issues, like indigestion and acid reflux, particularly in individuals already susceptible to these problems. The impact of eating before a workout will likely have depends on the type of exercise you’ll be doing and the intensity.
A low to moderate-intensity walk probably won’t cause digestive issues and may actually improve digestion, but when you pick up the intensity, all bets are off. So, if you’re doing a high-intensity workout, it’s best to wait at least two hours after a meal before carrying out your sweat session. Even then, food will still have not moved completely out of your stomach and you’re still at risk for digestive issues.
Digestion is actually a slow process It takes 6 to 8 hours for food to move from your stomach into your small intestines. However, for most people, two hours after a meal is enough to avoid major digestive issues, although it varies from person to person. You might discover that your body needs three hours after a meal to accommodate a workout.
Feeling a Bit Heavy?
The other problem is the “full” effect. If you’ve ever eaten a large meal and tried to exercise, you probably felt heavy. How good will your performance be if you’re weighed down by a meal that’s still shifting around in your stomach? Plus, digestion is hard work! After a meal, your brain directs more blood flow to your stomach and intestines to supply the energy and additional oxygen these parts need to process the food you’ve eaten. That means less blood flows to the muscles you’re working and less blood and oxygen delivery to your brain. You probably won’t feel as motivated to work out due to the reduction in brain blood flow and will likely feel a bit sleepy.
In addition, the reduction in blood flow to your brain might even make you feel a bit lightheaded, especially if you bend over or get up off a mat too quickly. After a meal, your body goes into “rest and digest” mode, governed by the parasympathetic nervous system. In contrast, when you exercise, you ramp up the sympathetic, or fight or flight portion, of your nervous system. These two components have opposing actions. Once you start exercising, the sympathetic nervous system will win out and you won’t be able to properly digest your food. No wonder digestive issues are so common with exercise!
What about Strength Training?
You might feel too heavy after a meal to do a HIIT workout but what about strength training? Strength training doesn’t raise your heart rate as much. You might think that lifting weights right after lunch wouldn’t be a problem, however, that’s not necessarily true. Blood is still being diverted away from your muscles – not only could your performance be compromised but your chance of feeling lightheaded or dizzy is higher.
Remember, the digestive process is pulling blood away from your brain. When you pick up a pair of weights and start doing sets, more blood is diverted from your brain to your muscles. So, if you change positions too quickly, you could feel lightheaded or even pass out. So, it’s not a good idea to strength train right after a meal either, especially a large meal. Grabbing a small snack likely won’t have the same impact as a full meal. So, if you have to eat and then work out, keep the quantity that you eat small and eat the rest after your workout.
Exercising in a Fasted State
Some people deliberately exercise in a fasted state in hopes of burning more fat. Indeed, some studies show that stored body fat is mobilized and oxidized more readily when you’re in a fasted state. In one study, researchers asked healthy men to either skip breakfast or eat a 600-calorie meal after awakening. Both groups walked on a treadmill at a moderate pace for an hour. Upon checking their blood after the workouts, they found the men who exercised in the fasted state burned more fat, although their blood sugar was lower as well. The men who fasted also showed greater activation of genes involved in insulin sensitivity and preserving metabolic health. So, there may be advantages to exercising on an empty stomach as long as you’re not doing a high-intensity workout.
The Bottom Line
If you have to exercise after eating, make sure the meal or snack you eat is light, especially if you’re prone toward digestive issues. Ultimately, you’ll probably feel more comfortable waiting two hours after eating and because you feel less full, your performance will be better as well.
References:
Mayo Clinic. “Digestion: How long does it take?”
New York Times. “The Best Thing to Eat Before a Workout? Maybe Nothing at All”
Related Articles By Cathe:
5 Reasons You Feel Sleepy & Less Productive after a Meal & What You Can Do about It
Don’t Be Afraid to Split Up Your Exercise Sessions
5 Inconvenient Things That Can Happen During a Workout & What to Do About Them
