Carbohydrate back-loading, anabolic window, intermittent fasting, carbohydrate front-loading, fasted cardio and meal spacing, all of these terms fall under the nutrient timing umbrella.
Nutrient timing is simply a term used to describe the consumption of meals or different food types at different times of day, for example in the morning, before bed or pre- and post-workout. Many sports nutrition companies sell their products based on nutrient timing, and many fad diets revolve around eating at restricted times of the day or avoiding certain macronutrients at various times.
Despite a lot written about the subject, the question remains, does nutrient timing actually matter? How important is it for those with specific body composition or exercise goals?
Back in the 2000s, the effect of protein feedings spaced equally throughout the day (four meals containing 20g of protein each) on muscle protein synthesis was investigated. This was compared with eight smaller meals, containing 10g of protein each and two larger meals, containing 40g of protein each, after resistance exercise (Areta et al., 2013).
There was indeed a greater protein synthesis response after four meals compared to the other meal patterns. This suggests that four meals, or 80g of protein total, might be optimal for maintenance or attainment of peak muscle mass.
We now know that consuming meals of 0.4g protein/kg bodyweight of protein, three to four times per day, reaching a minimum of 1.6g/kg bodyweight/day is optimal for muscle building (Schoenfeld & Aragon, 2018). So daily spacing of protein meals, at least in terms of muscle building, is important and effective.
The Post-Workout Anabolic Window
The anabolic window, also known as the metabolic window, is the period after exercise when consuming protein and carbohydrates can shift the body from a catabolic to an anabolic state. It’s estimated that this window lasts around 30 minutes, though this is dependent on the individual and the type of exercise being performed.
What happens if a person doesn’t take supplements or consume food during this window, are they at risk of undoing their hard work or not reaping the full benefit of exercise?
In short, no, and research is conflicting as to whether protein straight after exercise is actually beneficial for muscle mass. Provided you consume a meal containing 0.4g/kg body weight of protein before training, the ‘window’ for consumption after training may be up to a few hours.
However, resistance exercise stimulates muscle protein synthesis rates and without protein ingestion, protein balance will remain negative. If this happens then protein breakdown occurs which is obviously detrimental to muscle growth. Therefore, post-exercise protein ingestion is widely accepted as a potential method to maximise the potential for muscle recovery and growth. This is more important when you head straight to training without prior meal consumption.
Protein before bed might also be important for muscle gain because this presents a prolonged window of fasting for most of us. Indeed, some research has identified an improvement in muscle mass and strength in response to 27g protein at night time as opposed to spreading over the rest of the day (Snijders et al., 2015). Further, up to 40g protein pre-bed may improve muscle protein synthesis (Res et al., 2012).
The problem with much of this research is that they have lacked a comparison with groups given the same amount of total protein. Nonetheless, protein ingestion at night is a potentially good method to ensure that you reach your target protein intake for the day.
So at least in terms of protein, spacing meals appropriately might be important. A good suggestion would be four meals with 0.4g/kg bodyweight protein, plus a pre-sleep meal of 0.6g/kg body mass for your last meal. If consuming one of these meals soon after training isn’t feasible then having a protein supplement after training won’t do any harm.
Whether it be avoiding carbohydrates at breakfast to ‘optimise fat burning’, or timing carbs only around training, to avoiding all carbs until the evening, post-training, many of us will have tried some carbohydrate timing in the pursuit of exercise goals. Simply put, however, eating carbohydrates at any time of day has the same effect. There is no need to stop eating carbs at a given time of day, or even start eating them at a given time of day.
However, timing your carbs around training may be important if you are in a state of calorie deficit. Carbs give us energy and when the weights start to feel heavier or the legs tired, having a bowl of warm oats before a training session might give you the boost that you need to fuel you to train harder than you would otherwise.
Carbohydrates and Sports performance
There’s a clear distinction between timing your carbohydrates for fat loss or muscle growth verses timing them for performance, specifically endurance performance (marathons, triathlons, intermittent sports etc).
If you are looking to improve athletic performance with nutrient timing, either for yourself or clients, then follow these guidelines:
1. Ensure that daily carbohydrate intake overall is sufficient to fuel performance. If the goal isn’t to lose body fat then roughly 5-10g per kg bodyweight/day should be consumed.
2. 36-48 hours before a competitive event lasting more than 90 minutes, consume roughly 10-12g carbohydrates/kg bodyweight per day
3. 60-90 minutes before your training or event, consume 1-4g/kg body mass of carbohydrates
4. Timing carbohydrates after completing your event isn’t crucial unless there’s another even on the same day
5. There may also be some benefit to training before eating. Fasted training can support molecular adaptions that may improve endurance performance
1. Know your goal – If it is fat loss or muscle gain, nutrient timing may not be a huge consideration. Total daily intake is of far greater importance. If the goal is performance, especially endurance, then the focus should be specifically on carbohydrate timing alongside other macronutrient intakes
2. Energy balance – If you want to lose fat, you will need to be in an energy deficit (taking in less than you expend). If you want to gain muscle, it will really help you to be in an energy surplus. This and your total daily macronutrient intakes matter far more than any nutrient timing
3. Do what you prefer – Remember that adherence comes first. Work from the general recommendations for your daily intakes and go from there. Nutrition is fun, so don’t ruin that by overthinking and over-restricting based on some metaphorical rulebook that doesn’t actually have any underpinning evidence
Areta, J.L., Burke, L.M., Ross, M.L., Camera, D.M., West, D.W., Broad, E.M., Jeacocke, N.A., Moore, D.R., Stellingwerff, T., Phillips, S.M. and Hawley, J.A., 2013. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. The Journal of physiology, 591(9), pp.2319-2331.
Res, P.T.; Groen, B.; Pennings, B.; Beelen, M.; Wallis, G.A.; Gijsen, A.P.; Senden, J.M.G.; van Loon, L.J.C. Protein ingestion before sleep improves postexercise overnight recovery. Med. Sci. Sports Exerc. 2012, 44, 1560–1569.
Schoenfeld, B.J. and Aragon, A.A., 2018. How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition, 15(1), p.10.
Snijders, T.; Res, P.T.; Smeets, J.S.J.; van Vliet, S.; van Kranenburg, J.; Maase, K.; Kies, A.K.; Verdijk, L.B.; van Loon, L.J.C. Protein ingestion before sleep increases muscle mass and strength gains during prolonged resistance-type exercise training in healthy young men. J. Nutr. 2015, 145, 1178–1184