The principles of nutrient timing are based on the physiology of the human body. Known scientific facts govern the application of these principles as the body is better able to assimilate protein and deliver these nutrients, along with other important micronutrients, macronutrients and energy substrates to muscles at specific times of the day.
This means that by knowing when to ingest a precise dose of nutrients you can optimise your muscle-building efforts and improve recovery, while also minimising muscle damage. The key to understanding the science of when to eat centres around the hormonal changes in the body that happen due to a number of factors.
Factors like glucose tolerance and insulin sensitivity are constantly altered during the course of a day, which means that the body goes through various catabolic (breaking down) and anabolic (building up) states. Exercise also stimulates the release of a number of catabolic and anabolic hormones.
The resultant hormone-driven catabolism is actually an important part of the anabolic process as we need to “disassemble” nutrients for energy production and the repair of cells, especially muscle cells. The main exercise-induced catabolic hormones are epinephrine, norepinephrine, cortisol and glucagon.
During exercise epinephrine and norepinephrine levels become elevated to assist with energy production from fat and glycogen. These hormones also increase heart rate, blood pressure, heart contractility, blood redistribution to muscle and respiration rate to meet the physiological demands that exercise places on your body.
Cortisol is also responsible for the breakdown of carbohydrates and fat for energy during exercise. Cortisol production is activated by low blood glucose levels, which generally results from intense exercise. If you are in a glycogen-depleted state (from insufficient carbohydrate intake), cortisol will convert protein (from food or muscle) into amino acids, which are then sent to the liver to make glucose in process known as gluconeogeneses. This makes cortisol one of the most powerful catabolic hormones in the body and we therefore need to counteract its ability to destroy muscle if we wish to continue developing the physiques we are after. Glucagon also stimulates fat breakdown and helps to raise blood glucose levels by increasing the release of glucose. It can also increase the rate of gluconeogeneses.
Anabolic hormones such as insulin, testosterone, IGF-I and growth hormone support muscle growth, tissue repair, control inflammation and also facilitate the regulation of carbohydrate, fat and protein metabolism.
Insulin causes cells in the liver, skeletal muscles and fat tissue to absorb glucose from the blood. Insulin sensitivity increases during and directly after exercise, which enhances glucose uptake and accelerates the transport of amino acids into muscle cells.
Another important anabolic hormone that is released following intense exercise is testosterone, which plays a pivotal role in both protein synthesis and muscle hypertrophy. Growth hormone is responsible for stimulating IGF-I, a hormone that plays an important role in the development of mature muscle fibers from immature muscle cells, and also promotes protein synthesis.
During times when anabolism is highest, which generally occurs first thing in the morning, after a workout or at night while sleeping, the body is primed for muscle gain.
It is therefore important to ensure that we feed the body with the right type and amount of nutrients at these crucial times (meal composition and portions are both important factors, but are beyond the scope of this article).
It is also important to note that because the body swings from one state to the next during the course of the day, some foods are not optimal during certain times of the day, but may become beneficial during other times.
The ingestion of the appropriate amount and type of fat, carbohydrates and protein at the right times will therefore enhance glycogen synthesis, replenish glycogen stores, decrease muscle inflammation, increase protein synthesis, maintain continued muscle cell insulin sensitivity, enhance muscle development, encourage faster muscle recovery and boost energy levels.
With so much to gain from proper nutrient timing and so much to lose from the wrong approach, it pays to be clinical in your approach to meal and supplement timing-
The energy, anabolic and growth phases
In the book, Nutrient Timing: The Future of Sports Nutrition the authors, Dr. John Ivy and Dr. Robert Portman refer to three critical times of the day when nutrient timing is of utmost importance. These phases are the energy, anabolic and growth phases.
THE ENERGY PHASE
Occurs during the workout when energy demands are highest. These demands are met by either ingested nutrients and/or stored nutrients. Numerous studies have shown that ingestion of a whey or protein blend supplement that contains some form of carbohydrate like glucose and/or maltodextrin is the ideal form of nutrition to begin the anabolic process without causing digestive or intestinal discomfort during training.
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. This results in increased muscle cell membrane permeability, which means that it is vitally important to the anabolic process that you ingest highly bioavailable protein and a source of carbohydrates to ensure glycogen and amino acids can be shuttled into muscle cells for growth, repair and recovery This is best achieved by drinking a whey protein shake with a source of high glycaemic carbohydrates. The other anabolic hormones also begin working during this period to repair the muscle and decrease inflammation. However, this phase can also add to the catabolic effects of exercise if no nutrients or the incorrect nutrient ratios are consumed during this vital phase. It is only through adequate nutrition and supplementation that the body can recover and grow, bigger and stronger than before, following exercise.
THE GROWTH PHASE
Considered to be the 18-20 hours post-exercise when muscle repair, growth and strength occur. The aim during this phase is to prolong and promote additional anabolism through your diet. Consuming a protein and carbohydrate meal within three hours of your training session will stimulate further protein synthesis.
The other important period during the growth phase is sleep. Adequate sleep of 8-9 hours a night is essential to the recovery and repair process as the body releases a cascade of anabolic hormones during this time, most far in excess of the quantities released during the day. It is therefore essential that we supply the body with a rich source of nutrients to promote further anabolism and assist the repair process during sleep. It is for this reason that slow digesting protein supplements, in the form of a casein-based shake, have gained such popularity. Consumed in combination with a rich source of healthy fats, which will limit the rate of gastric emptying, these supplements can supply a steady trickle of amino acids to growing muscles throughout the night.