March 13, 2013 by Armi Legge
Want to gain muscle? Then…
1. Lift weights.
2. Eat — a lot.
If you’re doing those two things — you’ll grow.
However, according to many sources, when you eat might be more important than how much.
In theory, you’ll recover faster and gain more muscle and less fat if you eat as soon as possible after your workout.1,2 Preferably within at least 30 minutes — a period called the
“anabolic window.”
There are a few rare situations when this is probably true. Most of the time, however, you don’t have to be this rigid about when you eat to achieve optimal muscle growth.
Note: This article covers the need to eat after weight lifting for muscle growth, not after endurance training for recovery. That’s for another article.
3 Reasons Eating After a Workout Might Increase Muscle Growth
After extensively reviewing the literature on this topic, Alan Aragon and Brad Schoenfeld summarized the three main theoretical reasons why it’s important to eat after exercise for muscle growth:3
1. Replenish muscle glycogen.
2. Halt protein breakdown.
3. Stimulate protein synthesis.
1. Replenish muscle glycogen.
Training with low muscle glycogen has a negative effect on muscle growth.
After exercise, your muscles are better able to turn glucose (sugar) into glycogen. This effect disappears soon after a workout. Therefore, eating carbs about 1-2 hours after a workout will restock glycogen levels much faster than if you wait. This will, in theory, increase muscle growth and recovery.
2. Halt protein breakdown.
If you want to gain muscle, protein synthesis (anabolism) has to be greater than protein breakdown (catabolism).
Protein Building – Protein Breakdown = Muscle Growth or Loss
After a workout, muscle proteins degrade and rebuild faster than normal (increased protein turnover). In theory, consuming protein and/or carbs soon after a workout will stop muscle proteins from being broken down sooner, largely by spiking insulin levels. If fewer muscle proteins are destroyed after each workout, this could increase muscle growth over time.
3. Stimulate protein synthesis.
Eating protein after a workout is supposed to optimize the other side of the same equation by increasing muscle protein synthesis. This boost in protein synthesis after each workout is supposed to increase muscle mass.
All of these theories make sense. However, there’s good reason to believe none of these short-term effects are as important as they might seem.
Why Most People Don’t Need to Eat Immediately After a Workout for Optimal Muscle Growth
In most cases, you don’t need to eat immediately after lifting weights to optimize muscle growth.
Photo via Flickr
If you wait to eat carbs several hours after your workout, your glycogen levels will still be restocked about 8-24 hours later.4,5
The only time it’s probably necessary to consume carbs in the post-workout window is if you perform at least two glycogen depleting workouts, with the same muscle group, within eight hours.6 If you don’t eat carbs soon after the first workout, you may not be ready for the second.
Even if you exercise the same muscle group twice per day, you’ll still probably have enough muscle glycogen to perform well in the second workout.
A moderate volume workout of around 6-9 sets per muscle group only depletes about 36-39% of your muscle glycogen.7,8 If you do more than that in two workouts within eight hours, eating carbs soon after your first workout is a good idea.
You’re probably still digesting your last meal after a workout.
If you’ve eaten a normal meal several hours before your workout, your insulin, amino acid, and glucose levels are still going to be high several hours after the workout.
Most mixed meals will keep your insulin levels high enough to stop protein breakdown for 4-6 hours.9 A 45-gram dose of whey protein will do the same for about two hours.10 Technically, a single meal before your workout could “… function as both a pre- and an immediate post-exercise meal…,” writes Aragon and Schoenfeld.3
There’s also emerging evidence that increased protein synthesis, rather than decreased protein breakdown, may be the main trigger for muscle growth after exercise and eating.11 Interestingly, eating protein post-workout doesn’t seem to matter for this purpose either.
You don’t need to eat immediately after exercise to maximize protein synthesis (and it might not matter if you did).
Most studies have shown that if you eat protein before, immediately after, or several hours after your workout, your muscle protein synthesis will be about the same.12-14 As long as you consume enough protein by the end of the day, your body generally has no trouble growing new muscle tissue (assuming a semi-normal meal schedule of 2-4 meals throughout the day).
On the other hand, one study found that consuming essential amino acids and sucrose (sugar) before strength training did not increase muscle protein synthesis afterwards compared to fasting.15 These inconsistent results imply that “…the available data lack any consistent indication of an ideal post-exercise timing scheme for maximizing MPS [muscle protein synthesis],” writes Aragon and Schoenfeld.3
It’s also debatable how important the immediate rise in protein synthesis is after exercise, since a significant portion of muscle growth occurs later. Protein synthesis rises significantly about 3-4 hours after exercise, peaks at about 24 hours, and returns to normal 36-48 hours later.16-18 Furthermore, the short-term rise in protein synthesis after exercise does not always predict long-term muscle gain.19
Assuming the short-term rise in protein synthesis after a workout will produce long-term muscle growth, “…is speculative, at best.”3
If you eat enough protein by the end of the day, you probably aren’t losing anything in terms of muscle growth, regardless of whether you eat it post-workout.
On the other hand, several studies have shown that eating protein and/or carbs around exercise can increase muscle growth and strength, compared to eating earlier or later.
However, subjects in two of these studies consumed pre- and post-exercise nutrition20 (and in one case, also creatine),21 which makes it impossible to tell if the post-workout meal increased muscle growth. In contrast, two other studies have found no difference in muscle growth or strength when subjects ate protein immediately before and after workouts compared to those who did not.22,23 Overall, the evidence is not clear if eating post-workout will help you gain more muscle.
In another study, the group who ate immediately after exercise also ate more total protein, which may have helped them gain more muscle.24 Several of these studies also used untrained or older subjects, and the results might not be as relevant for trained weight-lifters or younger athletes.
That said, there are a few times when you’ll probably gain more muscle if you eat soon after a workout.
When Eating After a Workout May be Best for Muscle Growth
After fasted training.
If you train after an overnight fast (i.e. in the early morning before breakfast), you may get better results if you eat protein and carbs immediately afterwards.
Protein breakdown is higher after fasted training.25 Eating soon afterwards will decrease protein breakdown, which may increase muscle growth over time.26
If you don’t have time to eat after a fasted workout (or don’t want to), you may be able to limit protein breakdown by consuming some protein beforehand. As little as 6-10 grams of essential amino acids or 20 grams of whey protein can keep your amino acid levels high for around 2-3 hours.14,27,28
You can probably get the same benefits from branched chain amino acids (BCAAs), which are thought to be the most important amino acids for muscle growth. 29-33 They can also favorably affect gene expression for muscle growth when consumed before fasted training.34
There’s also some short-term data showing fasted training might be better for muscle growth, assuming you eat afterwards.35
Training more than 3-4 hours after your last meal.
Training 3-4 hours after a meal isn’t technically fasting, but it may be long enough to make post-workout nutrition more important for muscle growth.
A normal mixed meal will keep amino acid levels high for about 5-6 hours.36 After a 45-90 minute workout, plus time to shower, drive home, etc, your amino acid levels almost will be back to fasting levels. In this case, eating some protein (>25 grams) may be best if you’re trying to gain muscle.3
However, you can still probably work around this by consuming a small amount of protein beforehand like you would for fasted training.3
If you’re leaner and/or more experienced.
If you’re leaner or you’ve been training for a while, you may need to be more careful about eating around your workouts. However, it’s still up for debate if you need to eat post-workout. Eating several hours pre-workout may work just as well.3
If you’re depleting the same muscle group of glycogen multiple times per day with exercise.
If you perform at least two glycogen-exhausting workouts, with the same muscle group, within eight hours, you may need to eat within 1-2 hours after the first workout.6 If you don’t, you may not be recovered for the next session.
However, most people trying to gain muscle don’t train this much or this often. You’d probably have to do about 20-30 sets per muscle group in each workout (at least twice a day) in order to require an immediate post-workout meal to optimize recovery for the second workout.
If you’re an older athlete trying to gain muscle.
Older people often don’t gain as much muscle with the same amount of weight training and protein intake as youngsters, a phenomenon called “anabolic resistance.”37 Eating extra post-workout protein may help overcome this problem.3
One study found that 74-year old men who ate protein and carbs immediately post-workout gained more muscle and strength than those who ate 2-hours after exercise.38 However, another study found that elderly men did not gain more size or strength when they ate protein immediately before and after exercise or a placebo.39
A Simple Formula for Eating to Gain Muscle
In the same review mentioned earlier, Aragon and Schoenfeld created a simple formula for around-workout nutrition to maximize muscle growth:3
Eat about 0.4-0.5 grams of high quality (high in BCAA) protein per kilogram of lean body mass in your pre- and post-workout meal.
Here’s how to use this formula if you weigh 100 kilos at 20% body fat:
1. Find your lean body mass.
100 kilos (220 pounds) * lean body mass (.8) = 80 kilos
2. Multiply your lean body mass by 0.4 and 0.5.
80 * 0.4 = 32
80 * 0.5 = 40
In this case, you would want to eat between 32 and 40 grams of protein in your pre- and post-exercise meal. This would be equal to about 1.5-2 skinless, boneless chicken breasts, or 1.5-2 scoops of whey protein.
Your pre- and post-workout meals should be at most 3-4 hours apart, assuming your workout is about 45-90 minutes. If you eat your protein in a mixed meal (with carbs, fiber, fat, etc.), you can probably wait 5-6 hours.
If you train fasted, eating about 6-grams of essential amino acids or branched chain amino acids, or 20-grams of whey protein before your workout can let you delay your post-workout meal for another 2-3 hours. When you do eat, it’s probably best to shoot for the upper end of the protein recommendations — 0.5 grams per kilogram of lean body mass or slightly more.
It doesn’t matter when you eat carbs for muscle growth as long as you eat enough by the end of the day.
The Post-Workout “Anabolic Window” is Much Wider Than You Might Think
If you want to gain muscle, you need to eat after exercise. How soon you eat is not usually as important.
Over the long-term, most studies have shown that you don’t need to eat immediately after exercise to optimize muscle growth. There are certain situations where it may be more important, but there are still a few shortcuts to make your eating schedule more flexible.
As long as you hit your total calorie and macronutrient goals by the end of the day, post-workout nutrition is not usually crucial for muscle growth.
In later articles we’ll explore nutrient timing for endurance sports. Click here to subscribe by email to have these articles delivered to your inbox.
A special thanks for Alan Aragon and Brad Schoenfeld for their excellent review on this topic that was the primary inspiration for this article. Alan was also kind enough to review and approve this article before it was published.
Disclosures: None.
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