Updated: Mar 5, 2019
This is a very controversial topic lately, with one group giving a lot of importance to post workout anabolic window where if you do not consume a quick digesting protein shake immediately post workout, you will not grow. The other group went to the other extreme, claiming that anabolic window does not exist, and that total daily protein intake is what matters. If you consume enough protein throughout the day, meal timing does not matter at all.
While I am glad that the era of drinking protein shakes mixed with dextrose in the changing room right after your workout is over, I still have a problem with the new ''anabolic window does not exist'' approach simply because it is not true. It does exist and we will see how we can take the most advantage out of it to maximize our muscle growth.
The anabolic window
The anabolic window can be defined as a period of time with an elevated muscle protein synthesis. You can think of this as a period of time where energy intake and protein maximizes muscle growth.
Anabolic window duration depends on the training level of each individual. Untrained individuals have an anabolic window that can last up to 72 hours, which makes nutrient timing practically irrelevant. Just consuming equal amount of protein, preferably 0.4 g / kg of body weight, in every meal is sufficient for optimal muscle growth.
This however changes very quickly with trained individuals as the body adapts to strength training and post workout muscle damage decreases. As a result, muscle protein synthesis duration rate decreases as well. In trained individuals, MPS may still be elevated 29 hours after the training session, but peak MPS occurs much earlier. For the comparison, see the graph below.
As you can see, for trained individuals, the peak muscle protein synthesis occurs within the first 8 hours post workout after which it sharply declines. On the other hand, untrained individuals experience an elevated MPS initially, with a peak close to 20 hours post exercise. This simply means that nutrient timing is not important for untrained individuals, while this completely changes for trained individuals.
To take advantage of an elevated muscle protein synthesis, we need to sync our protein intake with the period where your body needs protein the most. Since it takes time (1-2 hours) for amino acids to reach blood and muscles after you consume a meal, for trained individuals it becomes very important to consume a pre workout meal. If you train fasted, it is already too late to maximize post workout protein synthesis. A general recommendation that I give to my clients is to consume at least 0.3 g / kg of body weight of protein 1-2 hours before workout.
When an anabolic window opens in the post workout period, this is the time where the ceiling effect of protein synthesis is higher, meaning you can consume more protein with a higher chance of being used for muscle repair and growth instead of being oxidized for energy or even converted to glucose.
For example, if you train 3 days per week, you will experience much higher levels of protein synthesis around those 3 days, which is why it would be beneficial to increase your protein intake during that period and decrease it while you are outside of the anabolic window, simply because protein requirements are significantly reduced.
You want to synchronize blood hyperaminoacidemia with the maximal ceiling of muscle protein synthesis meaning your blood should have enough amino acids in the post workout period. Specifically, you need to think in terms of hours and not days. For example, if you train in the evening, you want to maximize the amount of protein intake in the post workout meal (dinner) and also your breakfast even if the following day is your rest day. The reason why is that your breakfast is still within the anabolic window with a higher ceiling effect.
This does not mean that your overall protein intake should be higher, it only means that you need to allocate it more carefully with more protein within anabolic window and less protein outside of it for better nutrient partitioning.
Lets see what the studies say.
Keim and bros (1997) compared two groups on a weight loss program. The difference between the groups was that one group consumed most of their food (70%) in the AM while the other group consumed 70% of their energy intake in the PM. Caloric intake was equated, and both groups had the same exercise program with a combination of resistance training with cardio between 9:00 and 11:30 in the morning. As a result, the PM group, consuming most of their energy in the post workout period, gained more strength, lean muscle tissue and lost more fat mass.
Burk et al (2009) compared two group where the only difference was the timing of a protein supplement containing 70 grams of protein. One group consumed it pre workout while the other group consumed it post workout closely before going to bed. As a result, the post workout group gained significantly more muscle mass than the group consuming it midday.
Cribb & Hayes (2006) reached a similar conclusion, where the group that consumed more protein around workouts gained more lean muscle tissue compared to the group that did not.
Now that we are sure that anabolic window actually exists, lets see what kind of protein should be consumed for maximal muscle growth.
One of the most important indicators of protein quality is its leucine content. Leucine is a branched chained amino acid that stimulates mTOR enzyme that functions line an activation switch for muscle protein synthesis. But simply consuming BCAA as a supplement without any protein might be counter productive. For leucine to work it needs to have enough protein as building blocks to build muscle. Without it its like trying to flip a light switch without electricity, nothing happens. This is why BCAA as a supplement is useless in isolation.
Another determinant of protein quality is the food matrix. The more whole the protein source, the better it is at stimulating protein balance. For example, casein and milk protein are better at stimulating protein balance than whey protein. Also whole milk is better than skimmed milk.
On the other hand, many plant based protein sources have a negative effect on protein balance because they contain anti nutrients that limit the absorption of protein.
Absorption speed also determines the quality of protein. Supplement companies led us to believe that faster protein is better protein. Ultra fast absorbing proteins are also the most expensive proteins on the market. But how does this affect protein quality? The main argument for fast proteins is higher protein spike. While this is true, this spike quickly goes down meaning it does not last long. Slower proteins like casein stimulate muscle protein synthesis for a much longer period of time, and this is the key.
Fast absorption can result in higher oxidation rates which results in fewer amino acids being incorporated into muscle tissue. It simply decreases the amino acid uptake by your muscles which results in less muscle growth.
Post workout carbohydrates
Consuming any type of carbohydrates post workout together with protein does not increase protein balance. To spike up the insulin for maximal protein balance, a dose of only 20 g of protein is sufficient. Consuming any type of carbs on top of this is just adding more energy, nothing else.
If you are working out in the evening, it may be beneficial to back-load most of your carbs in the evening as the research shows some small benefits of this.
- Greater weight loss with a greater decreases in abdominal circumferences.
-A greater decrease in fasting insulin levels.
- A greater increase in HDL (good cholesterol)
For strength trainees, insulin action may be more anabolic due to reduced glucagon levels and you might see an improvement in sleep as well because carbohydrates affect serotonin production which affects melatonin production that puts you to sleep. Having a large carbohydrate meal 1-2 hours before bed might be beneficial.
When it comes to the glycogen levels, strength training can hardly deplete 30% of your glycogen stores, and studies have shows full glycogen replenishment within 6 hours post workout without any food intake. However if you engage in endurance type of activities, glycogen replenishment becomes more important as glycogen stores are easily depleted.
Overall, carbohydrate intake does not have as big of an impact as protein timing when it comes to muscle growth. It might slightly improve nutrient partitioning if you consume it post workout.
Fats timing does not does not matter and can be distributed evenly throughout the day.
To maximize muscle growth, protein timing should be incorporated in your meal program. You can implement this by consuming 0.3 g / kg of body weight per meal outside your anabolic window, and consuming 0.6 - 0.8 g / kg of body weight per meal within your anabolic window. This will maximize your muscle growth by syncing your protein intake with an increased muscle protein synthesis and higher ceiling effect. During this time, it is best to consume high quality protein from a whole food animal source as plant based protein contains anti nutrients that limit the absorption of protein. Total daily protein intake should be 1.8 -2.0 g / kg of body weight.
Carbohydrates and fats can be increased as well during an anabolic window as combining all three macro nutrients increases metabolism by increasing the thermic effect of food and therefore, your expenditure. The type of carbohydrates does not matter as long as you meet your daily fiber intake. If you struggle to meet your daily fiber intake, consume carbohydrates that are rich in fiber like fruits, legumes, and potatoes. You should not completely exclude one macro nutrient from any meal during the day. It is about allocating ratios.
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