Common bodybuilding wisdom holds that you should eat a massive meal right after a training session if you want to maximize muscle growth. Since many people find it hard to eat a big meal right after exercising, a whole sub-industry of post-workout protein supplements has sprung up to fill this “need.”
Like much common exercise physiology wisdom, it holds a grain of truth, but misunderstands important aspects of human biology (in this case, digestion and anabolic signaling).
As you’ll see, post-workout nutrition does matter, but less than many people (and the supplement industry) want you to think. Instead, you might benefit from listening to your body when it tells you that it’s not hungry until a few hours after your gym session.
The Importance of Nutrient Timing Depends on the Nutrient
It’s important to remember that that your body is capable of storing nutrients for later, but how long it can store them for depends on the nutrient.
You have, of course, enough stored fat to last you for weeks. However, stored fat can only be burned for energy, so you still need to eat some fat to meet your body’s structural and hormonal needs. Overall, fat is not very timing-dependent at all.
Carbohydrates are stored as glycogen in your liver and muscles. You store roughly an 18-48 hour supply, depending on your activity level. Unlike fat, carbs are somewhat timing-dependent.
Protein stands out here in that you don’t really have a “storage tank” for it. Your body keeps maybe 50 grams of amino acids floating around in the bloodstream, plus you have protein (hopefully) digesting at any given time. But beyond that, your muscle tissue is your body’s way of storing protein and amino acids, so if you go too long without eating protein, your muscles can start to be cannibalized for raw material, as it were. Still, you have at least a few hours of leeway here.
Vitamins and minerals mostly fall into two distinct categories: fat-soluble and water-soluble. Fat-soluble micronutrients like vitamin D are stored in your fatty tissue, so you store several weeks’ supply of them, just like fat itself. Water-soluble vitamins and minerals like vitamin A, on the other hand, are not stored long-term. Like protein, you need to consume them at least once a day — if not with every meal — to maintain stable levels.
Finally, some minerals like calcium are stored in bone tissue, where they’re used for structural purposes but can be leeched out if needed. You should also be consuming these minerals regularly to avoid this, but you have more leeway in timing than with water-soluble minerals.
How Pre- and Peri-Workout Nutrition Factors In
After eating, food takes about 6-8 hours to pass through the stomach and small intestine (where most digestion takes place), and another 24-30 hours to pass through the colon for the final stage of digestion.
Right from the start, this should illustrate something vital about post-workout nutrition: Much of it actually starts pre-workout. In order to have the needed nutrients hitting your bloodstream post-workout, you need to have eaten a healthy meal or high-protein snack in the 2-3 hours before your workout, and another healthy meal 3-6 hours before that.
Likewise, it means that peri-workout nutrition — the fuel you consume during a workout — isn’t crucial if you handled your pre-workout nutrition. You don’t need to consume a protein shake in the middle of your gym session. Studies show that peri-workout protein doesn’t make a difference as long as total daily protein intake is kept constant and sufficiently high.
You might need to consume water and/or a sports drink during longer endurance activities however, as hydration and electrolytes do deplete and digest quickly enough to make a noticeable difference.
Your Post-Workout Meal Is Crucial Sometimes. Here's Why.
Research shows that timing nutrient intake (protein in particular) around your workouts is far less important than ensuring adequate overall intake.
How much is adequate? You need to eat at least 0.4 grams of protein per kilogram of body weight per meal, and your total protein intake should exceed 1.6 grams per kilogram of body weight per day.
Furthermore, these should be spaced evenly enough that there’s always some protein digesting. Since this mostly happens in the small intestine and food takes 6-8 hours to make it through the stomach and small intestine, that means that meals should be spaced no more than 6 hours apart during the day.
But What About the Anabolic Window?
Now with all of that said, it is true that it helps to feed your body extra nutrients — particularly protein and some carbohydrates — during the post-workout anabolic window. It’s not just a matter of your body needing the nutrients. An energy surplus also increases anabolic signaling mechanisms such as mTOR, although research is divided on how big the effect is.
However, that window is longer than people think, particularly if you’re not at an advanced level yet. And contrary to popular assumption, the strength of the anabolic stimulus is actually higher near the middle of that window — 12-24 hours post-workout — than it is during the first few hours after a workout.
All of that is to say three things.
First, because the time scales involved here are in the range of 6-8 hours for individual meals and 12-48 hours for post-workout anabolic windows, timing overall doesn’t require that much precision.
Second, because the anabolic window is so long, post-workout nutrition should be thought of in terms of your next two or three meals after a workout, rather than your next single meal.
And finally, because the anabolic window grows before it shrinks, you don’t need a big meal right after a workout. In fact, you may be better off making the next meal after a workout close to normal-sized, and the meal after that one more notably large.
All of this depends on when you train, of course. If you train in the evenings and only have time for one meal before you sleep (meaning your next meal would be 12-14 hours post-workout), then that pre-bed meal needs to be big. But if you train in the mornings, your post-workout nutrition can easily be spread out over the rest of the day.
All in all, you should calorie cycle a bit — eating more during that post-workout window and less outside of it — but you need to be flexible about timing it with your lifestyle. Thankfully, the nature of both muscle hypertrophy and food digestion allows you to be flexible.