Nutrient Timing: “It’s About Time”

Lorenzo Wimmer

September 01, 2016

growth nutrients timing

Throughout our lives, we all know that timing IS everything. It is becoming increasingly evident in endurance performance sports that this is a cornerstone of being able to “go the distance”. We are all looking to improve our muscle strength and power, our stamina and hopefully our body composition as a result of proper nutrition. A regular exercise regimen coupled with good nutrition will enable the body to achieve optimal performance. The question now is, “what to eat, when”. Today, I will give you some of the science behind nutrient timing in achieving your personal health and performance goals, and help you understand how timing is crucial in helping to repair damaged tissue, restoring proper physiological function and depleted glycogen stores, while building muscle for future events.

For years, serious athletes, and weekend warriors alike, searched for the “Holy Grail” of exercise and nutrition, to build strength, endurance and lean muscle mass. Wisdom from the 60’s and 70’s told us we need to super-saturate our muscles with carbohydrate, and “carbo-loading” was the “magic bullet” for cyclists and runners for the time. Strength building athletes found that high protein intake was the recipe for success, thus flipping the carb loading idea on it’s head.

Every new fad seemed to be missing strong scientific evidence. Until a man named Dr. John Ivy came into the picture. Dr. Ivy, the Chairman of the Department of Kinesiology and Health Education in the College of Education, University of Texas at Austin, looked at simple, healthy options for building strength, endurance and muscle mass. He found that there was one key element missing in the equation for success – timing.

“When you exercise,” says Ivy, “the muscles become very sensitive to certain hormones and nutrients, and you can initiate many highly desirable training adaptations if you make sure the correct nutrients are present.
This increased sensitivity of the muscles only lasts for a limited length of time, so the element of time becomes absolutely crucial. If you miss this window of opportunity, there’s no way you can stimulate the muscle adaptations to that extent until after the next bout of exercise.” (1)

The Phases of Nutrient of Timing

1) The “Energy Phase”, just before a workout or an event
2) The “Fueling Phase, during the event (not so much in just a workout)
3) The “Anabolic Phase”, the timing just after an event, 30-45 minutes
4) The “Growth Phase”, the time up to 18-20 hours post event/workout

Circadian Rhythms
Many of our events start early in the morning, just prior to or just after daylight. This is the optimal time to take in fuel to begin our journey.Why? It is important to consume our first meal with the onset of light, as our ”central clock” is entrained by food and sunlight for our entire day. Our hormones also are regulated by food and light, as well as energy demands from extreme exercise. Insulin, an anabolic hormone, and insulin receptors are more sensitive in the morning. Since we have been asleep, we have been “fasting”, thus hunger coupled with daylight from sunrise make it an optimal time to fuel our body.

In the last two articles, we learned about sugars, glycogen and fats, and how much we have stored for exercise for events that are long in duration. Remember that we only have stored, about 90 minutes of glycogen (stored sugar) in our muscles and liver for intense exercise. After that, the body will break down fats and protein to use as fuel.

The Energy Phase
The goals of our Energy Phase are to increase the nutrient delivery to muscles, stave off glycogen and muscle protein loss, limit the suppression of our immune system response to inflammation, and nutritionally prepare for a faster recovery (especially important in Stage Events). Depleting our energy stores (glycogen) is a major factor in acute muscle fatigue and weakness.

Consuming carbohydrates, proteins and electrolytes in 14-20 ounces of water 30 minutes prior to exercise, raises blood sugar levels, has been shown to stimulate protein synthesis after exercise and aides in muscle recovery.

But how much of each and when?

Dr. Ivy’s research finds that about 1.4 g of carbohydrate per kg of body weight will optimize glycogen storage. An initial ratio of 4:1 carbs to protein seems to be optimal for improving endurance, reducing muscle fatigue and speeding the recovery after exercise.

In one study with cyclists, Ivy discovered that drinking a fluid containing carbohydrate and protein in a 4:1 ratio improved endurance 57 percent compared with water, and 24 percent compared with a carbohydrate drink. Because muscle breakdown occurs faster during exercise, consuming a supplement that includes protein while exercising gives muscles some of the protein they need to produce extra energy. The result is less muscle damage. Similarly, maintaining blood glucose levels by ingesting carbohydrates during exercise leads to less depletion of glycogen stores and less fatigue. (1)

The Fueling Phase
Last month we talked about fats, how they are more calorie dense than sugars and proteins, and their importance in endurance exercise. The amounts and types of food that you will need to consume during your event will vary by your age, sex, body type, dietary restrictions and preferences. This would include solid foods containing proteins and fats such as peanut butter, coconut oil, or energy bars. It is important that we eat solid foods that will release nutrients slowly, rather than ingesting only liquids for our energy needs. Having a metabolic assessment to determine you hourly caloric expenditure and VO2Max would be helpful. Not over or under-eating at an aid station is as important as your timing. On my endurance cycling events in the past, I watched people consume enough food at the first aid station to choke a horse. Knowing what you’re really burning, versus what you THINK you’re burning are often very different.

I know that I burn at my low level of effort, about 575 kcal/hour, whereas Peter Fain, at full tilt, may burn more than 1,200 kcal/hour. So at this phase, your maintenance fueling phase, the timing should be about the same as your fluid intake, about every 20 minutes to stay ahead of your estimated expenditure.

The Anabolic Phase or Re-building Phase
In the 30 minutes following an event, the muscle’s potential to rebuild peaks, and it is extremely sensitive to insulin. This phase is also has a critical time limit, as the window of time for insulin sensitivity. This is your “Post Event” re-fueling phase. This window of time is only open for about 30-45 minutes post event, and should start within 15 to 30 minutes post event. When our bodies are most sensitive to insulin, we are able to replenish glycogen that we have depleted and help feed our muscles with protein that was broken down during extreme exercise.

Consider this your “Performance Zone”.(2)

Growth Phase
Once you have started refueling within that window, the body will remain sensitive up to 18 to 20 hours, as your body continues to replenish and build new tissue. This metabolic window of opportunity is very important in making you a stronger athlete for your next event, especially if competing in a staged event. I should stress the importance of sustained, low insulin spikes during this 18 to 20 hours post event/workout. Eating a combination of complex carbohydrates (such as sweet potato) and proteins (meat, chicken, fish, legumes) in a 3:1 combination every 2 to 3 hours will help rebuild muscle and replenish glycogen very effectively.(3)

One very important part of this equation that is not nutrient based is your recovery time, which goes back to your natural circadian rhythm, and that is sleep – and the timing for starting your sleep. Your body’s recovery and repair happens when you sleep, and the best amount of repair begins before midnight. The fewer hours of sleep before midnight, means less deep sleep and adequate recovery.

More on that next month when we will talk a little more about our body’s internal clock, and the use of anti-inflammatory drugs before during and after exercise.


(2) Excepts from The Performance Zone, by Dr. John Ivy
(3) Duggirala, C., M.D., Wimmer, L., CEC. Fuel, Inc.

Burke, L.M., Kiens, B., & Ivy, J.L. (2004). Carbohydrates and fat for training and recovery. Journal of Sports Sciences, 22, 15-30.

Chambers, A., Kravitz, L. (2009). Nutrient Timing: The New Frontier in fitness performance. AKWA: The Official Publication of the Aquatic Exercise Association, 22(4), 4-6

Haff, G.G., Kock, A.J., Potteiger, J.A., Kuphal, K.E., Magee, L.M., Green, S.B., & Jakicic, J.J. (2000). International Journal of Sport Nutrition and Exercise Metabolism, 10, 326-339.

Levenhagen, D.K., Gresham, J.D., Carlson, M.G., Maron, D.J., Borel, M.J., & Flakoll, P.J. (2001). Postexercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis. American Journal Physiology – Endocrinology and Metabolism, 280, 982-993.

To sleep, perchance to dream