Aerobic exercise reduces fat faster on an empty stomach

Fasting aerobics can indeed increase the proportion of fat energy supply during exercise, but whether it can help you lose weight faster and whether you can persist in the long term depends entirely on your body's tolerance and all-day diet control. It is a bonus for fat loss, not a must-have, and it is not a magic method for fat loss suitable for everyone.

The first time I came into contact with fasted aerobics was when I was preparing for competitions in 2018. At that time, my body fat was stuck at 17% and I couldn't get rid of it. The coach asked me not to eat when I got up every morning, just drink a cup of black coffee without sugar and then climb the stairs for 40 minutes. At that time, I really watched the fat on both sides of my waist shrink. In less than three weeks, my body fat dropped to 14%, and even my abdominal muscles became much clearer.

In fact, the logic behind it is very easy to understand. Just like if your mobile phone is fully charged and played for a whole night, the power of the fast charger is almost exhausted, so you can only use the spare battery for emergencies. You have slept for 7 or 8 hours without eating anything, and the glycogen stored in the previous day has been depleted. If you do low-to-medium intensity aerobics at this time, your body cannot use glycogen for energy as it does after a meal. It can only mobilize more fat to decompose to provide energy for exercise. This is not made up by fitness bloggers. It has been verified in the field of exercise physiology: for the same 30 minutes of low- to medium-intensity aerobic exercise, the energy supply ratio of fat can reach 60%-70% on an empty stomach, but only about 40% if done one hour after a meal. The data difference is indeed there.

But why has this statement been argued for almost ten years without a unified conclusion? It's really not a groundless argument. A while ago, I met a little girl who was 160cm tall and weighed only 92kg. Her body fat was only 21%. I heard on the Internet that aerobic exercise on an empty stomach would help her lose fat faster. She got up every morning and ran 5 kilometers. Within a week of running, she fainted in the community. She was sent to the hospital and was told that she had low blood sugar. She even tore a big piece of her knee. And what the opponents say about "fasting aerobics to lose muscle" is not alarmist. If you don't have high muscle mass, but you still do high-intensity fasted aerobics for more than an hour as soon as you start, when the body's energy supply is not enough, it will really break down the muscles to get energy. By then, not much fat will be lost, but the muscles will be lost first, and the basal metabolism will be reduced. If you drink cold water later, you will gain weight, which is not worth the loss.

Interestingly, if you ask fitness practitioners in different fields, you may get completely different answers. Most bodybuilding coaches will tell you not to do fasted aerobics for too long. A maximum of 20 minutes of climbing is enough. After all, they want to preserve muscle. It is much harder to lose a pound of muscle than to gain a pound. ； But if you ask marathon or triathlon coaches, they will proactively arrange for their team members to do long-distance training on an empty stomach on a regular basis. The purpose is to improve the body's fat metabolism. During the competition, when the glycogen is depleted, it can still rely on fat to provide energy, so as not to "hit the wall" halfway. Essentially, everyone has different goals, and no one is right or wrong.

To be honest, if you want to try fasted aerobics, you should first understand your own situation. If your body fat rate is already high, more than 20% for boys and 25% for girls, and you don’t feel dizzy or flustered when you wake up in the morning, or have basic diseases such as hypoglycemia or heart disease, you can definitely try it. Pay attention to controlling the time, no more than 45 minutes at most, and the intensity varies. If it is too high, you can climb stairs, briskly walk, or do low-intensity exercises at home. It is enough to control the heart rate at (220-age) × 60%-70%. You can drink a cup of black coffee or light salt water before exercising. Don't touch sugary drinks, otherwise the advantage of fasting will be lost. Don't delay eating after exercise. Eat some protein and slow carbohydrates within 15 minutes to half an hour. Just two eggs and a piece of whole wheat bread will do. Otherwise, you will lose muscles if you are hungry all morning.

If you are already thin, have a low body fat percentage, or feel dizzy when you get hungry in the morning, then there is really no need to join in the fun. My friend is prone to hypoglycemia. He followed the trend and climbed stairs for two days before, feeling dizzy every time. Later, he changed to walking in the park for 40 minutes an hour after dinner every day. The caloric difference throughout the day was maintained at about 300 calories. He still lost 8 pounds in two months, and his body fat dropped by 3%. There was nothing wrong with him.

I don’t do fasted aerobics every day when I’m doing liposuction. I only do it three times a week. The rest of the time is after strength training, I add 20 minutes of climbing. Occasionally I’m craving for an extra piece of cheesecake, and I’ll make up for it by climbing the stairs for an extra 10 minutes the next day. Really, there is never a standard answer to fat loss. Don’t deify any method, and don’t follow the trend. If you try it yourself and feel comfortable, able to persist, and don’t rebound after falling off the scale, that is the best method.