With all the information out these about the best diets for muscle growth, fat loss and general health, you’ll likely hear a lot about the importance and relevance of nutrient timing.
This dietary principle is based on the biology and physiology of the human body. The theory suggests that the body goes through natural cycles or phases of tissue building (anabolism) and tissue breakdown (catabolism) throughout the day.
Body building
During anabolic phases, the body is supposedly primed to break down and absorb ingested protein and deliver amino acids, along with other important micronutrients, macronutrients and energy to muscles than at other times during the day.
Generally, the times when anabolism is highest are:
- First thing in the morning upon waking.
- Within 60-90 minutes after a workout.
- At night while you sleep during the first phase of your sleep cycle.
A phased approach
This theory was popularised by respected scientists Dr. John Ivy and Dr. Robert Portman, who authored the book Nutrient Timing: The Future of Sports Nutrition in the early 2000s.
This became the reference guide to most sports nutritionists for the past decade. In the book, Ivy and Portman outline three critical times of the day when nutrient timing is most importance. These phases are the:
- Energy phase
- Anabolic phase
- Growth phase
The energy phase occurs during the workout when energy demands are highest. These demands are met by either ingested nutrients and/or stored nutrients.
The anabolic phase occurs immediately after a workout and lasts for up to two hours. This phase is generally termed the “anabolic window” or “window of opportunity” because muscle cells are most receptive to ingested nutrients during this time due to heightened insulin sensitivity and the resultant increase in cell membrane permeability.
This is why it is advised that you ingest a highly bioavailable protein source along with a source of carbohydrates to ensure glycogen and amino acids can be shuttled into muscle cells for growth, repair and recovery.
The growth phase is considered to be the 18-20 hours post-exercise, including sleep, when muscle repair and growth occur. The aim during this phase is to prolong and promote additional anabolism through your diet by continuing to ingest sufficient protein.
However, it is generally advised that you eat more fat and fewer carbs during this period as immediate energy demands are lower.
The hormone factor
The key to understanding the science of when and what to eat centres around the hormonal changes in the body that happen due to numerous factors.
For instance, glucose tolerance and insulin sensitivity vary during the course of a day due to a various factors, including meal timing and meal composition. Exercise also stimulates the release of numerous hormones.
There are many athletes who follow this approach and have had success with it. However, it now seems that there are differing opinions on the importance of such specific meal and nutrient timing strategies.
However, most of criticism of this approach is based on the fact that the studies used to justify this approach were short-term studies. Also, many studies used elite athletes as subjects, making the results largely irrelevant to the average person who trains for just an hour a day.
There is also new science showing that meeting your total protein intake over the course of a day is sufficient to ensure optimal muscle protein synthesis.
Individualised approach best
That’s not to say a specific approach is wrong, but rather that there are different schools of thought now and that the principle of individual difference dictates that an approach that works for one person may not work as well for someone else.
So don’t get bogged down in the detail and don’t become too neurotic about nutrient timing – or at least how quickly you can chug down a protein shake after a workout.
While some form of carb manipulation is generally beneficial as insulin is a powerful hormone, both in terms of anabolism and fat storage, overall, as long as you are hitting your macronutrient ratios and total recommended intakes, you should make progress in terms of your physique.
Author: Pedro van Gaalen
When he’s not writing about sport or health and fitness, Pedro is probably out training for his next marathon or ultra-marathon. He’s worked as a fitness professional and as a marketing and comms expert. He now combines his passions in his role as managing editor at Fitness magazine.
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