Does Protein Timing Matter? — Interview with Dr. Bill Campbell

For decades, the idea that you have to eat protein immediately before/during/after a workout has been hotly contested.

Shiva Best
Aug 21, 2018 · 6 min read
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Is the smoothie lifting weights? Is the dumbbell sipping a drink? Not sure what’s going on here.

Proponents will say you can’t make gains without it, while critics argue it doesn’t matter one bit. To get the real answer, we spoke to one of the best researchers in the world of protein supplementation: Dr. Bill Campbell.

Q: What is “protein timing” and what’s it supposed to do?

A: Protein timing is consuming protein around the time of your workout. It could be right before, during, or right after your workout.

In theory, ingesting protein right before or right after your workout makes amino acids (leucine in particular) available to your muscles when they need it most. Some people believe that there is a “window of opportunity” when muscles are more receptive to taking those available amino acids and incorporating them into newly formed skeletal muscle proteins (i.e., myosin) and improving recovery. So, if you incorporate protein timing, you’re providing your muscles with amino acids at a time when they will be directed towards the adaptive processes of building muscle and aiding in recovery.

Q: Is there a real benefit to eating protein immediately before/after a workout?

A: I believe there is. I’m basing my opinion on the available research which I will summarize here. There have only been 5 studies in healthy individuals that have investigated this topic (the purpose of the studies was to investigate the timing of protein intake in conjunction with resistance exercise). Of these 5 studies, 3 showed a positive effect for protein timing and 2 reported no benefit for protein timing on muscle mass gains.

The two best studies conducted on this topic reported conflicting outcomes. Dr. Jay Hoffman (1) provided a protein supplement to resistance training football players either right before and right after their training or in the morning and evening (hours away from the resistance training session). At the end of the 10-week study, there were no differences in muscle mass gains between the two groups. In contrast, an Australian study (2) reported that when a protein/creatine/glucose supplement was ingested before and after resistance exercise as opposed to in the morning and evening (hours away from the resistance training stimulus), there were positive outcomes. Specifically, lean muscle mass was significantly greater in the group that ingested their protein-containing supplement around the time of their workouts.

In another study, untrained elderly men took a protein supplement immediately after resistance training or 2 hours after training during a 12-week training program. At the end of the study, it was reported that those subjects ingesting the protein supplement immediately after the workout significantly increased their quadriceps muscle cross-sectional area (CSA) by 7%, while the group that waited two hours to ingest the protein supplement didn’t see any gains in muscle.

In a younger population (4), untrained males took a protein supplement immediately before their late morning workouts or waited until the evening to consume their protein supplement. In this study, the subjects that waited until evening to take their protein supplement increased their lean body mass by 1.8% as compared to 1% in the group that ingested their protein immediately before their workout. There was no significant difference between the two protein timing treatment groups in relation to lean body mass gains.

The final study investigated the effects of consuming a protein supplement snack prior to a resistance exercise workout and compared this to ingesting nothing prior to working out. At the end of the 5-week training period, it was reported that the protein timing group significantly increased their lean body mass (2%) and muscle cross-sectional area (2.8%) of the forearm flexors.

As I said, I’m basing my opinion on all the studies specifically designed to look at the effects of protein timing on muscle mass. Of these 5 studies, 3 reported favorable results with protein timing and 2 reported no benefit. I side with the science!

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Q: What about taking casein protein before bed?

A: While I think it’s a good practice to take protein (casein, whey protein, or any other high-quality source) before bed, there’s no scientific evidence to support that casein ingestion before bed is beneficial for inducing gains in lean body mass.

There are two studies on this. One study (6) reported that casein protein ingested prior to sleep significantly increased quadriceps muscle cross-sectional area. However, a closer inspection of this study revealed that those who ingested the nighttime casein protein also increased their total daily protein intake from 1.3 to 1.9 g/kg/day. So, were the gains in lean muscle mass due to the nighttime casein intake or were they due to the increase in total daily protein? Unfortunately, we can’t know for sure. The other study that looked at nighttime casein intake reported no benefit in terms of lean body mass gains when compared to morning casein intake (7). However, in this study total daily protein intakes were equal between the protein treatments.

Q: Does it matter if you get protein from powders (like whey) or whole foods (like chicken)?

A: In terms of lean body mass adaptations, the answer is no. However, if you’re dieting, I believe there’s a benefit to getting protein from whole food sources (like chicken breast) because this could keep you fuller.

Q: What do you think everyone should know about supplementing with protein?

A: I think the most important consideration for protein intake is the total daily amount of protein consumed each day. This is where everyone should start — find out how much protein you need to consume each day. Once you have this amount, I think it makes sense to divide this total protein into 3–5 protein meals throughout the day (whatever works best for your lifestyle) and to plan on making one of these protein ‘meals’ a liquid supplement that you take right after your workout. Part of my justification for this strategy is that if you need to ingest protein anyway, why not plan to have one of these protein meals around the timing of your workout? A majority of the research looking into this topic supports this practice.

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Q: Is there a downside to taking protein at certain times, such as around your workout?

A: No, there’s no downside. I’m not aware of any studies in which protein ingestion around your workout will negatively affect muscle mass, health, or exercise performance.


There you have it! While it doesn’t sound like we know for sure that it will build extra muscle, taking protein right after your workout is still a good idea backed by science and experts. It can help you hit your daily protein and might just boost your gains! Isn’t that a good enough reason to try it?

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About Dr. Campbell

Dr. Bill Campbell is a professor of Exercise Science at the University of South Florida. He has been researching protein supplementation and resistance training for 15 years, and his recent projects include optimal protein intakes for female physique athletes, the effects of diet re-feeds in resistance training individuals, and the importance of training frequency on maximal strength adaptations. You can follow Dr. Campbell’s research on Instagram: @billcampbellphd


  1. Hoffman JR, et al. Effect of protein-supplement timing on strength, power, and body-composition changes in resistance-trained men. Int J Sport Nutr Exerc Metab. 2009 Apr;19(2):172–85.
  2. Cribb PJ, Hayes A. Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy. Med Sci Sports Exerc. 2006 Nov;38(11):1918–25.
  3. Esmarck B, et al. Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans. J Physiol. 2001 Aug 15;535(Pt 1):301–11.
  4. Burk A, et al. Time-divided ingestion pattern of casein-based protein supplement stimulates an increase in fat-free body mass during resistance training in young untrained men. Nutr Res. 2009 Jun;29(6):405–13.
  5. Kato Y, et al. Chronic effect of light resistance exercise after ingestion of a high-protein snack on increase of skeletal muscle mass and strength in young adults. J Nutr Sci Vitaminol (Tokyo). 2011;57(3):233–8.
  6. Snijders T, et al. Protein Ingestion before Sleep Increases Muscle Mass and Strength Gains during Prolonged Resistance-Type Exercise Training in Healthy Young Men. J Nutr. 2015 Jun;145(6):1178–84.
  7. Antonio J, Casein Protein Supplementation in Trained Men and Women: Morning versus Evening. Int J Exerc Sci. 2017 May 1;10(3):479–486.

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