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Nutrient timing involves eating foods at strategic times in order to achieve certain outcomes.

It’s supposedly very important for muscle growth, sports performance and fat loss.

If you’ve ever rushed for a meal or protein shake after a workout, this is nutrient timing.

However, despite its popularity, the research on nutrient timing is far from convincing (1).

Here is everything you need to know about nutrient timing.

If you’ve ever rushed for a meal or protein shake after a workout, this is nutrient timing. Photo credit: TeamGetFit
If you’ve ever rushed for a meal or protein shake after a workout, this is nutrient timing. Photo credit: TeamGetFit

A Brief History of Nutrient Timing

Nutrient timing has been used by professional bodybuilders and athletes for more than 50 years and many aspects of it have been studied (2, 3, 4).

One of the world’s leading researchers in carbohydrate timing, Dr. John Ivy, has published many studies showing its potential benefits. In 2004, he published a book called Nutrient Timing: The Future of Sports Nutrition.

Since then, many nutritional programs and books have promoted nutrient timing as the key method for losing fat, gaining muscle and improving performance.

However, a closer look at the research shows that these findings are far from conclusive and have two significant limitations (1, 5):

1. Short-term blood markers: Many of the studies only measure short-term blood markers, which often fail to correlate with long-term benefits (6).

2. Ultra-endurance athletes: Many of the studies follow extreme endurance athletes, which do not necessarily represent the average person.

For these reasons, the findings in much of the research that supports nutrient timing may not apply to everyone.

Bottom Line: Nutrient timing has been around for several decades. Many people believe it’s vitally important, but the research has limitations.

The Anabolic Window: Fact or Fiction?

The anabolic window is the most commonly referenced part of nutrient timing (7).

Also known as the window of opportunity, it’s based on the idea that the body is in the perfect condition for nutrient absorption within 15–60 minutes after exercise.

However, even though research on the anabolic window is far from conclusive, it is regarded as an important fact by many professionals and fitness enthusiasts.

The theory is based on two key principles:

1. Carb replenishment: After a workout, an immediate supply of carbs helps maximize glycogen stores, which can improve performance and recovery.

2. Protein intake: Working out breaks down protein, so post-workout protein helps repair and initiate growth by stimulating muscle protein synthesis (MPS).

Both of these principles are correct to some extent, but human metabolism and nutrition are not as black and white as many people like to think.

Carb Replenishment

One main aspect of the anabolic window is carb replenishment, since carbs are stored in the muscles and liver as glycogen.

Research has shown that glycogen is replenished faster within 30–60 minutes after working out, which supports the anabolic window theory (8, 9).

However, timing may only be relevant if you are training several times a day or have multiple athletic events within a day. For the average person who works out once a day, there is plenty of time to replenish glycogen at each meal (10).

Additionally, some research actually shows training with lower muscle glycogen to be beneficial, especially if your goal is fitness and fat loss (11).

New research has even shown immediate replenishment may reduce the fitness benefits you receive from that session (12).

So although immediate glycogen synthesis makes sense in theory, it does not apply to most people in most situations.

Protein Intake

The second aspect of the anabolic window is the use of protein to stimulate muscle protein synthesis, which plays a key role in recovery and growth.

However, while muscle protein synthesis and nutrient replenishment are important parts of the recovery process, research shows that you don’t need to do this right away after a workout.

Instead, focus on your total daily protein intake and make sure you eat high-quality protein at each meal (13).

A recent meta-analysis by leading researcher Dr. Brad Schoenfeld also arrived at this conclusion, summarizing that daily protein and nutrient intake is the priority (13).

In short, if you meet your total daily needs for protein, calories and other nutrients, the anabolic window is less important than most people believe.

Two exceptions are elite athletes or people who train several times per day, who may need to maximize fuel replenishment between sessions.

Bottom Line: The anabolic window is a period of time after workouts that is said to be crucial for nutrient intake. However, studies show that most people don’t need to replenish carb or protein stores right away.

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