Exercise When Your Stomach Is Empty, Effectively Burning Fat Faster?

JAKARTA - Many people believe that exercising before breakfast can make the body burn fat faster and lose weight. But is that true?

According to Javier Gonzalez, professor of nutrition and metabolism at the University of Bath, there is little truth in this assumption.

"When we exercise, the body always burns a combination of energy, especially carbohydrates and fat," Gonzalez explained, as reported by The Guardian's website on Saturday, November 22, 2025.

"If we fast overnight, usually the body will burn more fat and less carbohydrates than if we have breakfast, let alone a high breakfast of carbohydrates," he continued.

But this doesn't mean training when an empty stomach is more effective at losing weight.

"You can only store a small amount of carbohydrates as glycogen in your muscles and liver. Additional energy, both from carbohydrates, fats, and protein, will eventually be stored as body fat," Gonzalez said.

"So to lower fat, the most important thing is the calorie deficit by burning more energy than consumed. Otherwise, whether we fast or eat first, the body will balance it over time," he added.

Even so, exercising during an empty stomach still has benefits, especially for metabolic health. Fasting exercises can help muscles adjust to exercise and regulate blood sugar.

"The exercise while fasting seems to encourage muscles to move glucose from the blood, thus helping to control blood sugar, especially after eating," Gonzalez said.

This benefit is most felt in endurance, such as running or cycling. However, in high intensity training, such as sprints, the body still relies heavily on carbohydrates. So the effect of exercise when the stomach is empty is excessive.

"The most important thing is to keep exercising. Is it done when the stomach is empty or has eaten is just an addition," Gonzalez said.

If you want to try, start slowly with a duration of 15 to 20 minutes and increase it gradually. "If you feel dizzy or weak, it's a sign to stop and eat something." Gonzalez said.