Aug 26, 2025
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by Michal Jetelina

Anabolic window: does it really matter when we eat?

Aug 26, 2025
0 comments
by Michal Jetelina

A woman is preparing protein for a shaker.

The term anabolic window is known in fitness culture as a short, usually thirty-minute period of time after training, in which the muscles are “open” to nutrient intake more than at any other time of the day. For many years, it was believed that in order to maximize the effect of training and for muscles to start growing, it is necessary to supply nutrients to the muscles as soon as possible. As a rule, for this reason, a large number of athletes mixed protein in the gym locker room . In some cases, we can still encounter this phenomenon today. But is there any truth to it? And do we have to start mixing protein immediately after the activity or decide what to eat after training ? The latest studies provide a clear answer .

Where did the term anabolic window come from?

The idea that there might be a time period after training in which it is appropriate to supplement nutrients to increase muscle protein synthesis ( in simple terms, the process of creating proteins from amino acids, which after training serves to repair damaged areas in the muscle and to grow it - ed. note ) is based on several short-term studies. These have shown that after training, the body's insulin sensitivity increases for a short time and that when protein is supplemented immediately after exercise, the ability of muscle protein synthesis increases slightly . However, many studies have followed that have not confirmed this effect to the extent that was originally believed. Increased insulin sensitivity after training therefore exists and cells are somewhat more open to food intake, but this does not have a significant effect on protein synthesis itself. ^{1, 6}

Is there an anabolic window? Yes, but…

Recent studies show that it is not necessary to supplement nutrients immediately after training . Anabolic processes after training last up to 24 hours , not the mythical 30-60 minutes, as was often believed. Muscles are more sensitive to protein intake during this time period, and anabolic processes are more intense in the first few hours after training .

New studies show us that the mythical few-minute window in which you have to eat to avoid losing everything does not exist. We can replenish a sufficient amount of protein throughout the day. In everyday life, nothing will happen if you eat protein at home or if you manage to eat, for example, 2 hours after training. You don't have to worry, whether you eat an hour or three will not have any significant effect on muscle growth. ^{1, 6} On the contrary, it is important to ensure that you have sufficient total protein intake.

A woman runs on a treadmill with a breathing apparatus for measurement.

What happens in the body after training?

We damage muscles through training and deplete or reduce glycogen stores , after training, muscle fibers are repaired and energy losses are replenished. It is during the repair and regeneration process that muscles grow . Training is therefore a stimulus for muscle growth, and the growth itself occurs after training. ^{2, 6}

In order for our body, exhausted by training, to have enough energy and the necessary nutrients for recovery and regeneration, it is necessary to provide the body with an appropriate post-workout diet . The exact composition will vary depending on the type of activity, but we should never forget about proteins. Proteins are the basic building blocks of muscle and it is therefore not surprising that if we want to support its growth and regeneration, we must not have a shortage of them. They serve to support protein synthesis and prevent muscle catabolism.

Simply put, they support the most effective anabolic phase after training that has a catabolic effect on the muscles. This is especially true for strength training , which causes greater damage to muscle fibers. On the contrary, in most cases there is no extreme energy loss and therefore we do not necessarily need to supplement a significant amount of carbohydrates.

During endurance training, the rate of muscle damage is lower, but glycogen stores are depleted more rapidly. Therefore, after endurance training, the proportion of protein in the post-workout meal may be lower and we should focus on replenishing the missing energy in the form of carbohydrates. ³

In any case, we should not forget about post-workout meals and we should think about their composition, lack of energy and nutrients can negatively affect regeneration. However, it is not necessary to have a snack ready in the locker or buy it at the gym bar.

Is there anything I can do to restore and grow muscle mass?

Of course! We greatly influence protein synthesis by the overall composition of our diet. To optimize it, we should consume 1.4 - 2 g of protein per 1 kg of body weight. It is ideal to spread this intake throughout the day so that one serving of food contains between 20g and 40g of protein. ⁴

A man exercises his arms on a weight machine in the gym.

Is it necessary to buy BCAAs?

If we focus on the composition of proteins, the amino acid Leucine is important. It is one of the nine essential amino acids , our body cannot produce it itself and therefore it is necessary to supplement it from the diet . Together with isoleucine and valine, it forms a group of amino acids known as BCAA (branched chain amino acids) .

Leucine is, among other things, able to influence the initiation of protein translation (part of the formation of protein structure) and thus contributes to muscle proteosynthesis (the formation of muscle proteins). So if you are supplementing proteins after training, the optimal dose of leucine for protein synthesis is 0.7-3 grams . ⁴ However, it is definitely not necessary to buy BCAA supplements, BCAAs occur naturally in proteins , as amino acids are their basic building block . So after training, we can supplement them with, for example, easily digestible whey protein with a natural composition .

What do you take from this?

When replenishing energy after training, you certainly don't have to worry that if you haven't eaten within 30 minutes, you've missed the anabolic window and worsened your chances of muscle growth, this is not the case. However, it is advisable to replenish energy and nutrients properly after training, so that the body can get back into balance after exhausting activity and work on the processes of regeneration and growth of muscle mass. A sufficient amount of protein in the diet plays a key role, so include it in meals after training, in larger quantities after strength training, a smaller amount will suffice after endurance training, where it is advisable to replenish enough depleted energy with carbohydrates.