The main objective was to observe how different doses of whey protein and casein protein supplementation before sleep may effect resting metabolic rate, the rate at which your body burns energy when it is at complete rest, and the ability to perform resistance exercise the next morning.
“Previous concerns about pre-sleep feeding have been related to the belief that eating late at night leads to weight gain,” which is understandable as the rate is lower overnight, the researchers wrote.
“[But] recent pre-sleep feeding studies have shown that next morning RMR was increased or unhindered after consumption of low energy (~600 kJ; 150 kcals), protein dense foods prior to sleep,” they added, citing multiple studies on the subject that have been published in the past few years, including two published in the British Journal of Nutrition in 2014 and 2016.
However, though supplementation of 48 g of casein in this present study was linked to “favorable changes in morning resting metabolic rate” and some changes in resistance exercise performance, not all other doses did not show clear effects.
This small study of nine participants, conducted by researchers of Elon University in North Carolina, was published earlier this month in the journal Nutrients.
Supplements used in the study
Nine physically active young women participated in the study. This criterion meant that participants should have had regularly resistance trained two or more days per week for 12 months.
The study was a randomized, double-blinded crossover trial, which means each participants was randomly assigned using a computer generated randomization program to consume one of five supplements the night prior to each experimental trial repeatedly until they’ve supplemented with all doses and supplements.
These five were 24 g of whey protein, 48 g of whey protein, 24 g of casein protein, and 48 g of casein protein and a placebo called Propel Zero, a zero calorie electrolyte replacement drink by Gatorade. All protein powders came from the Glanbia Performance Nutrition owned Optimum Nutrition and was flavored vanilla.
Because the placebo differed in texture and flavor, it was the only supplement that was single-blinded to researchers but not to the participants.
‘A study sample size of nine seems a bit low’
“To date, only one other study has investigated the effect of pre-sleep nutrition on performance during a next morning exercise bout, and our study is the first to examine the impact of pre-sleep nutrient intake on next morning resistance exercise performance,” the researchers argued.
For the positive effect seen after supplementing 48 g of casein, the researchers proposed that “it is plausible that this dose was adequately digested and absorbed overnight, thus potentially having an impact on overnight recovery leading to the possibly trivial response in RE performance in the present study.”
Dr. Jose Antonio is CEO and co-founder of the International Society of Sports Nutrition and an Associate Professor and the Director of the Exercise and Sports Science program at Nova Southeastern University in South Florida.
Commenting independently on the study, he said that results should be taken with a grain of salt.
“A sample size of nine seems a bit low to garner really anything applicable to individuals that were not part of the study,” he said. “Heck, for me...measuring nine individuals is an okay day of data collection... But not for an entire study (even if it was a crossover design).”
However, he did not that the increase in resting metabolic rate is interesting. “It may explain in part the way high protein intakes promote fat loss.”
Published online, doi:10.3390/nu10091273
“Pre-Sleep Consumption of Casein and Whey Protein: Effects on Morning Metabolism and Resistance Exercise Performance in Active Women”
Authors: Takudzwa A. Madzima, Jared T. Melanson, Jonas R. Black, and Svetlana Nepocatych