Should you do aerobic exercise on an empty stomach or after eating?

There is no one-size-fits-all answer to this matter. It all depends on your exercise goals, physical tolerance, and the intensity of exercise you plan to do that day. Fasting and post-meal aerobics have their own applicable scenarios. There is no one who is more "correct" than the other.

Recently, I have read a lot of bloggers advocating that "fasting aerobic exercise can reduce fat twice as effectively as after a meal." There is a young girl around me who has just started working out. She believes it. She sets the alarm for six o'clock in the morning and gets up to do high-intensity exercises. After fifteen minutes of dancing, her vision goes dark and she almost falls to the ground. She is sent to the hospital and is told that it is hypoglycemia. This is the result of following the trend without understanding the applicable conditions.

The data in exercise physiology can indeed prove the advantages of fasting aerobics: after about 8 hours of sleep, the liver glycogen reserve in our body is only about 30%-40%. At this time, if we do low-intensity aerobics, the body will indeed switch to the fat energy supply mode earlier, and the proportion of fat consumption per unit time will be higher - but please note, it is the proportion, not the total consumption. And the premise is that you are doing fast walking, jogging, slow climbing stairs, low-intensity aerobics and other exercises that keep your heart rate at about 60% of your maximum heart rate. It is best not to exceed 40 minutes. If you don’t have a history of hypoglycemia, and you don’t feel flustered or tired after finishing it, but feel refreshed, then fasting aerobics is a good choice for you to use your time efficiently. For example, if I wake up 20 minutes early on a weekday morning, change my shoes and go downstairs to walk around the community twice, and then come back and have breakfast, I will be in good condition throughout the day.

But if you already have unstable blood sugar, or if you plan to do high-intensity exercise such as interval running, high-intensity HIIT, or long-distance cycling, then don’t force yourself into the excitement of fasting. When the energy supply is sufficient, your exercise performance will be much better, you can persist for a longer time, and your movements can be done properly. The total consumption will be much higher than if you are tired and paralyzed after 20 minutes on an empty stomach, and the fat loss effect will be better. Here we need to correct a misunderstanding that many people have: a high proportion of fat as energy supply does not mean that the total amount of fat is consumed. If you do 40 minutes of high-intensity aerobics after a meal, even if fat supplies only 40% of the energy, the total calorie consumption will be twice that of low-intensity aerobics on an empty stomach, and you will actually burn more fat.

And for people in the muscle-building period, aerobic exercise after meals can greatly reduce the risk of muscle decomposition. After all, no one wants to have the muscles they have worked hard for more than half a year to be consumed by several long periods of fasted aerobic exercise. Don’t think that you have to wait two or three hours before moving after eating. There are not so many rigid rules: if you eat solid food that is easy to digest, such as oats, boiled eggs, and whole wheat bread, waiting for 1 to 1.5 hours is about the same. ； If you just drink a cup of warm soy milk, eat a small banana or half a protein bar before exercising, then you can move in thirty or forty minutes without putting any burden on your stomach at all.

In fact, both groups in the current fitness circle have real supporters. When professional endurance athletes prepare for competitions, most of them will supplement fast carbohydrates before training to avoid losing strength and performance.； When many bodybuilding athletes brush fat before competition, they will regularly arrange fasting aerobics for less than 30 minutes 3-4 times a week to quickly reduce body fat rate. Both methods are supported by a large number of practical cases, and there is no one who is right or wrong. I planned to ride a 30-kilometer green road in a suburban county last Saturday. Before I went out, I ate half a corn and a small handful of blueberries. My legs didn’t feel weak during the ride, and I was able to stop and take photos along the way. ； If I had gone on an empty stomach that day, I would have had to buy energy gel from a roadside store halfway through the ride, which would have been more of a loss than a gain.

In fact, you really don’t have to worry about this. You can try it out over a couple of weekends and you’ll know which one suits you. Do it once on an empty stomach. I don’t feel dizzy or nauseous. I feel good after eating. So feel free to do it. ； If you feel lazy after exercising all day on an empty stomach and have no energy to even go to work, then take two bites of bread 10 minutes before exercising. The purpose of exercise is to make yourself more comfortable. There is no need to make yourself suffer and feel uncomfortable just to follow other people's "standard answers", right?