Pre-sleep protein: Its influence on metabolism, muscle growth, and fat loss
As we know, resistance training represents a potent stimulus to increase skeletal muscle mass and strength. However, without protein, net muscle protein balance will remain negative.
Protein intake shortly following exercise prevents breakdown of muscle protein (i.e., degradation) and enhances muscle protein synthesis rate which culminates in a net positive protein balance in this crucial period following exercise.
This synergy between nutrition and exercise on the post-exercise muscle protein synthetic response forms an essential principle that enables muscle to favorable adapt in size and strength to prolonged exercise training (1).
Muscle protein synthesis response following exercise is modifiable to the type, amount, distribution, and timing of protein ingestion.
Recently, the concept of protein ingestion prior to sleep has been introduced as an additional meal moment to increase daily protein intake and increase overnight protein balance, which could further enhance the skeletal muscle adaptive response.
But does it really help, and if so, how much should you have? Or will it make you fat?
These are a few questions we’ll dig into and provide evidence-based research on these questions. The aim is to give you clear information and practical strategies you can use to enhance your training efforts.
Pre-sleep protein digestion and absorption
Food consumption prior to sleep has recently received considerable media attention. It has been assumed for quite some time that food intake should be limited in the hours close to bedtime as it would have a negative impact on body composition and overall health, increasing the risk for cardiovascular diseases, such as obesity and diabetes (2).
Many believe that this food before sleep will turn into fat and make you fatter.
This may be the case when large quantities of food are ingested at night, but recent work in this area show there are positive physiological outcomes to consuming smaller and single macronutrient (i.e., protein) foods before sleep.
In addition, the advantages of night-time supply of nutrients for overnight recovery have been suggested to support muscle reconditioning and improve physical performance in athletes.
Pre-sleep protein and overnight recovery
Evidence shows that muscle protein synthesis rates were ~22% higher during overnight sleep when protein was consumed prior to sleep compared to participants ingesting a placebo (3).
Resistance-type exercise augments the overnight skeletal muscle adaptive response.
Muscle protein synthesis rates were 37% higher when 30g of pre-sleep protein was combined with a single session of resistance type exercise in the evening compared with pre-sleep protein only (4).
In support of the important stimulus of resistance exercise; 76% more of the pre-sleep protein derived amino acids were incorporated in myofibrillar protein when individuals engaged in resistance training earlier that evening.
It’s well-defined that prior resistance training enhances the efficiency by which pre-sleep protein derived amino acids are used in new muscle protein synthesis during overnight sleep (5).
It seems that quantity of pre-sleep protein is an important variable in older adults. In a recent study, 40 g of casein was compared to 20 g of casein with additional 1.5g of leucine and showed much greater benefit in muscle protein synthesis rates with 40 g (6).
This finding is similar to studies done in daytime showing that 20 g increases protein synthesis rates by ~75% in healthy young individuals, whereas an older population requires ~40 g to allow similar rise in muscle protein synthesis after eating (6).
As mentioned above, exercise further augments the rise in protein synthesis after eating in both young and older adults. It’s clear from research that 40 g of protein ingestion prior to sleep results in a positive overnight whole body protein balance in older adults (7).
It’s important to note that overnight muscle protein synthesis rates were significantly higher when older adults performed a single exercise session earlier that evening.
The existing studies suggest pre-sleep protein consumption as an effective strategy to maintain muscle mass via an increase in protein synthesis rates while sleeping. Ingesting 40 g of protein prior to sleep may not be practical for some, especially older adults.
Therefore, combining a potent stimulus (i.e. resistance exercise) earlier that day may increase the beneficial effects when consuming smaller amounts of protein (<40 g) prior to sleep (5).
Much of the research in the past utilized a pre-specified absolute amount of protein ingestion prior sleep and no studies have looked at protein relative to bodyweight or lean body mass (8).
After collapsing data sets on previously performed overnight muscle protein synthesis studies, it’s been shown that a positive association exist between relative protein intake (g/kg body weight, or g/kg lean body mass) and overnight muscle protein synthesis rates (5).
This positive association was observed in people who did and didn’t perform prior resistance-type exercise. In addition, both young and older adults showed similar trends.
More research is needed, but the available evidence points toward the concept that pre-sleep protein requirements may be personalized based on bodyweight or lean body mass. (See figure below)
Pre-sleep protein on fat-gain and appetite
When compared to a non-caloric placebo in healthy young men; consuming a pre-sleep caloric drink (containing mixed carbohydrate/protein) was shown to increase resting calorie expenditure without inhibiting fat burning (10).
These results coupled with an overnight increase in muscle protein synthesis rates following pre sleep protein ingestion imply that there is no effect on fat metabolism the next morning.
In addition, this may be a practical option to aid overnight muscle reconditioning and provide a competitive advantage to healthy young individuals/athletes. It was also shown in young obese men that pre-sleep protein intake didn’t affect fat or glucose metabolism, resting caloric expenditure or suppress appetite the following morning (2).
In summary, it turns out that pre-sleep protein does not blunt fat metabolism and may even help improve body composition over time.
Chronic effect of pre-sleep protein ingestion
There is very little research on the effects of long-term, chronic effects of pre-sleep protein on muscle growth and recovery. One study showed an increase in skeletal muscle mass and strength in healthy young men after 12 weeks of resistance training while consuming ~30 g protein versus a placebo prior to sleep (11).
We need to remember that this study compared pre-sleep protein supplementation with a non-protein placebo, and not to protein supplementation at other time points.
Therefore, we can’t definitively state that pre-sleep protein ingestion has surplus benefits compared with protein supplemented at other time points throughout the day.
It’s been hypothesized that pre-sleep protein supplementation increases muscle mass accretion during prolonged exercise training mainly as a function of increased total protein intake and distribution rather than by its specific timing before sleep (12).
As mentioned, there is very little solid research on long term effects of pre-sleep protein intake.
There is one recent study that used well-trained men and women and demonstrated an increase in fat-free mass. Although it wasn’t statistically significant; there was a numerically greater increase when protein was consumed in evening compared with the morning (+1.2 kg vs. =0.4 kg, respectively) (13).
Summary & practical applications
It’s clear from the evidence that protein ingested prior to sleep is effectively digested and absorbed during sleep, thus increasing plasma amino acid availability and stimulating muscle protein synthesis during overnight sleep in both young and old populations.
Prior resistance exercise in the evening combined with pre-sleep protein shows a further enhancement of overnight muscle protein synthesis rates. Therefore, consuming protein prior to sleep can be applied in combination with resistance type exercise training to further augment accretion in muscle mass and strength when compared with no protein supplementation.
However, it’s not fully clear if the beneficial effect on pre-sleep protein ingestion on muscle mass and strength gain during resistance-type exercise is due to an increased protein intake rather than by its specific timing before sleep; therefore, further research is necessary.
For now, a bolus of 30-40g of protein about 30 minutes prior to sleep is recommended to take advantage of this timing and enhance the overnight recovery process. Although most of the literature suggests whey or casein proteins, recent literature suggests no difference in muscle recovery after pre-sleep consumption of dairy- or plant-based proteins (rice/pea combination), so long as enough of each is consumed.
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8.Moore, D. R., Churchward-Venne, T. A., Witard, O., Breen, L., Burd, N. A., Tipton, K. D., and Phillips, S. M. (2015) Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. J Gerontol A Biol Sci Med Sci 70, 57-62
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12.Reidy, P. T., and Rasmussen, B. B. (2016) Role of Ingested Amino Acids and Protein in the Promotion of Resistance Exercise-Induced Muscle Protein Anabolism. J Nutr 146, 155-183
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