Many people going through a reduction diet put running, or other form of cardio exercise, into their schedule, and it’s usually performed on an empty stomach. According to a circulating opinion, this contributes to the efficient burning of excess fat. Allegedly to a much greater extent than in the case of post-meal exercise. Is this belief supported by scientific research? Does cardio exercise really make sense on an empty stomach? And is the result actually better than in the case of post-meal exercise? For many people, such behaviour is simply comfortable. They get up and can immediately go out for their training. They do not have to push anything in themselves, they do not have to wait for their meals to settle, so they don’t feel discomfort during exercise.
Running on an empty stomach - benefits
People that are against exercising on an empty stomach argue that such training does not make sense. This is not true, however. It may find use in certain situations. A good example would be people using the IF (Intermittent Fasting) protocol - a nutritional concept that introduces intermittent fasting.
Trainings in this case are performed very often many hours after eating. Contrary to what it may appear, such people have no problem with excessive catabolism. On the contrary, they effectively build muscle and burn fat.
Many studies have shown that intentionally delaying the intake of a first meal helps to get rid of excess fat. A few hours or several hours do not affect the rate of metabolism. Metabolism slows down after three days of starvation. In case of exercising on an empty stomach, after several hours of fasting, however, it is better to exercise strength than running. The resistance exercise activates the mTORC enzyme complex, which is responsible for initiating the synthesis of muscle proteins.
In case of running on an empty stomach, we should take special care of the post-workout meal!
The availability of nutrients in this case is small. For this reason, we should quickly supply the body with carbohydrates and a full-blown protein meal - leucine rich.
The advantage of exercising on an empty stomach is a better insulin response to carbohydrate intake after training. This may be important for better muscle regeneration and better muscle hypertrophy. Additionally, exercising on an empty stomach improves nutrient uptake during post-training, leading to better glycogen resynthesis. It can be up to three times higher than in the case of post-meal training.
As far as fat burning is concerned, it can actually be higher in case of cardio training on depleted glycogen stores. In the "cardio" training performed on fasting, after a few minutes the proportion of aerobic processes is predominant. It may be that up to 70% of the "burned" during aerobic fat training comes from intramuscular fat, not from free fatty acids.
Running on an empty stomach - side effects
Loss of thermogenic effect of food
When training on an empty stomach, we deprive our body of the thermal food. In other words, running fast we reduce our energy expenditure during exercise. Increased postprandial oxygen consumption (EPOC) has been observed in people who eat proteins and carbohydrates before workout. People who consumed a meal before workout also observed a higher body temperature.
Fat loss is the same in empty stomach and post-meal training.
Italian researchers conducted a study comparing fat burning for fasting and post-meal training. Researchers have concluded that post-meal training is more effective in fat burning. It was observed in the group after training a greater consumption of oxygen and higher calorie burning 24 hours after the training.
This means that we should not be worried about the consumed meal going towards the energy used during our exercise, instead of using the fat stored in the body. We can successfully do cardio training after a meal and gain as much satisfactory results as with empty stomach workouts.
High cortisol level at the morning
In the morning we have the highest daily cortisol concentration, and doing cardio training contributes to its further growth. High levels of cortisol can be harmful for both our health and our body. In the long term, high levels of cortisol cause fatigue, especially in the waist area.
Secondly, cortisol is a catabolic hormone. Its increased levels can lead to increased muscle tissue loss. Meanwhile, muscle tissue is fuelling metabolism and burning fat. For this reason, it should depend on our best behaviour. It should be added that carbohydrate intake can effectively lower cortisol levels. That is why it makes sense to eat a carbohydrate-containing meal before morning workout.
Training on empty stomach and training effectiveness
Taking morning workouts on an empty stomach can lead to another problem. Exercising on an empty stomach is not as effective as training after a meal. Some people are unable to function without eating, others will train and feel good. This does not mean, however, that they are doing their workouts to their full potential.
In conclusion, there are many opinions about exercising on an empty stomach that are not necessarily justified in science. Training after meal intake seems to be a more sensible and effective option. However, do not negatively deny empty training, as it can be used successfully.