Nutrition Timing Window

 August 23, 2017|  Lauren

Does the Post Workout Window Exist?

Nutrient timing comes from a long-standing belief that eating at specific times of the day can result in better muscle building outcomes. By manipulating macros – carbs and proteins during the post-workout periods it was thought an athlete could trigger an anabolic response, stimulating greater protein synthesis and glycogen up-take by the muscles than eating at some other time. This timeframe even got a special name – ‘the anabolic window’ or ‘window of opportunity’ but does the research actually support this theory or are you simply wasting your efforts trying to cram all that food in at one time?

The Post Workout Nutrition Theory

When you exercise, the body goes into energy wasting mode, expending ATP and breaking down glycogen into its most useable form glucose to make more ATP. When glycogen gets used up, the body will then turn to other energy sources to keep going including nitrates – aminos that are used to make muscle, and of course triglycerides or fat. Essentially if you have wasted all your glycogen the body will go into catabolic mode, breaking down your muscle, while ceasing protein synthesis or muscle building pathways from occurring. By providing your body with specific ratios of protein and carbs during the post-workout period you could essential stop catabolism, and stimulate anabolism by increasing insulin release.

Manipulating the Anabolic Hormone – Insulin

Insulin is the anabolic hormone responsible for shuttling glucose and other essential nutrients through the bloodstream to your muscles where they can halt catabolic processes and optimize muscle growth, repair and glycogen re-synthesis in preparation for your next big workout. By consuming a high ratio of carbohydrates to protein in a 2:1 ratio, low glycogen and amino levels could be restored. A positive insulin response could therefore increase muscle glycogen replenishment and increase protein and amino uptake into the muscle to trigger protein synthesis. Although this might seem pretty simple and rational, in actuality, most individuals who train never get to a point where they would truly be in a catabolic state, or completely depleted of glycogen!

Bro-Science? What Does the Research Actually Say?

Most studies that showed the positive effects of an anabolic window were completed on athletes that were in a fasted or semi-fasted state. Fasted means they abstained from eating for a pro-longed period of time before performing the test, which means providing any kind of food no matter carbs or proteins, would have a substantial insulinogenic effect! In fact, eating prior to your workout can do enough of spiking insulin to prevent catabolism for not just an hour but for many. What’s more, carbohydrates are not the only nutrient that can elicit an anabolic response. In fact, protein can also spike insulin release. One study showed that when supplementing with 6 g of essential amino acids immediately before exercise, muscle amino levels were elevated by 130% and remained elevated for two hours post-workout.
Further research showed pre-exercise consumption of 20 g of whey elevated muscular uptake of aminos 4.4 times pre-exercise resting levels during exercise and didn’t return to baseline levels until three hours post-exercise. These studies show that consuming a small pre-workout meal of protein can help sustain amino acid delivery to muscles post-workout, eliminating the need for a huge spike in blood sugar from a source of simple carbohydrates.

Is Glycogen Even Needed for Muscle Building?

When glycogen is low this can trigger a cascade of events that may block activation of major protein synthesis pathways that are regulated by insulin, and thus trigger catabolic processes including protein degradation or muscle breakdown. But, pathways of protein synthesis are mediated by more than just insulin. In fact, activation of muscle protein synthesis can be stimulated by the presence of aminos and even just the act of performing exercise. One study showed that high intensity resistance training with low muscle glycogen levels did not impair anabolic signaling or muscle protein synthesis during the 4 hours post workout recovery period. Another study showed that after a full body workout, adding carbs with protein didn’t increase whole body protein balance during a 6-hour post exercise recovery period to a greater extent than just protein only.

Real Life Application and Nutrient Timing

Bottom line, consistently providing the body with sufficient nutrients throughout the day will help to remain in an anabolic state and keep you there, even if you train with all out intensity! Exercise itself enhances insulin to take up and move glucose and nutrients in the body to where they need to be. Going longer than 3 hours between meals may result in nutrient depletion and thus reduce anabolic processes. However, true depletion of glycogen and aminos from your muscles is completely dependent on the individual.
The amount of calories and macronutrients you need post workout will be determined by the time of your last meal, intensity of your training, amount of available energy and even your gender. Women tend to reserve their glycogen and switch to fat as fuel over carbs. There is no one-fits-all method.

Realistically, replenishment to pre-training glycogen levels should not be a concern immediately post-workout. One study compared immediate post exercise ingestion of high glycemic carbs with a 2-hour wait before beginning recovery feedings and found no significant difference between the groups in their glycogen levels at 8 hours and 24 hours post workout. That means your total calorie and macronutrient intake for the entire day is far more important than eating immediately after your workout.
If your goal is to achieve a muscular, fit body, you will need to make sure your daily calorie and macronutrient ratios are appropriate for your goals. While nutrient timing can help you maximize muscle building and recovery, it’s not something you need to live your life by! Pay attention to how your body feels and responds to what you feed it and when you feed it. Make adjustments based on your own unique requirements and needs.


Aragon A, Schoenfeld BJ. Nutrient timing revisted: is there a post-exercise anabolic window. JISSN. 2013. 10: 5.
Burke, LM, et al. Carbohydrates and fat for training and recovery. J Sports Sci. 2004. 22:15-30.
Gibala, MJ. Nutritional supplementation and resistance exercise: what is the evidence for enhanced skeletal muscle hypertrophy. 2001. Can J Appl Physiol. 2000. 25(6): 524-535.
Levenhagen, DK, et al. Postexercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis. Am J Physiol Endo Metab. 2001. 280: 982-993.
Volek, JS. Influence of Nutrition on Response to Resistance Training. Med Sci Sports Exerc. 2004. 36(4): 689-696.
Volek, JS, et al. Nutritional aspects of women strength athletes. Brit J Sports Med. 2006. 40: 742-748.

 August 23, 2017 | Lauren

About the Author

Lauren Jacobsen is the Director of Nutrition for Kcal Brands and the Head of Fuel Up. Lauren has over 15 years of experience in nutrition and supplementation focused on physique athlete development. Lauren is also a former IFBB competitive figure athlete, and long time contributor to fitness magazines worldwide.

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