Interview with Dr. Bill Campbell on Meal Frequency and Nutrient Timing

Train Loco Nation! How we doing? Today we have a fantastic interview with Dr. Bill Campbell. We had the great privilege of meeting Dr. Campbell and discussing training and nutrition at the 2014 NSCA Conference in Vegas. We have a great deal of respect for Dr. Campbell and his lab as they are doing a great amount of research on bridging the gap between science and application in the physique development industry.  His lab focuses on improving performance and physique through resistance training and targeted supplementation and/or diet. So some really awesome things are being done at the University of South Florida lab.  Without further ado, lets get to know Dr. Campbell and talk meal frequency and nutrient timing!

– Chris and Eric



Bill: Before I begin my interview, I want to express how blessed I am that I now know the two of you.  I believe the two of you introduced yourselves to me at the 2014 NSCA National Conference in Las Vegas.  From that moment, I could tell that both of you live your passion – there is not a minute that goes by in the day where each of you are trying to improve your knowledge base so that you can be more effective coaches and professionals.  The way that each of you approach your profession is very inspiring to me and others that want to be the best at what they do.  I hope to get to know each of you better over time and to learn from you.


DDT: Thanks for the intro Dr. Campbell, it was an honor meeting you, discussing training and nutrition, and we look forward to furthering our knowledge through great mentors like yourself. With that said, let’s get this party started 😉 Could you give us a little background info on who Dr. Bill Campbell is?

Bill: I am an Associate Professor of Exercise Science at the University of South Florida.  I also am the Director of the Performance and Physique Enhancement Laboratory at USF. I received my PhD in Exercise, Nutrition, and Preventive Health at Baylor University in 2007.

I am extremely blessed to have the career that I have, I love to learn about exercise nutrition, research exercise and nutrition, and teach others about exercise and nutrition.

On a personal level, I am a follower of Jesus Christ and attempt to live my life in a way that glorifies Him.  I am married to a great woman and we have two daughters (7 and 4) whose macros are not counted every day.


DDT: What got you inspired and into the fitness-health-physique development industry? 

Bill: Bodybuilding.  When I was in my early 20’s, I was a natural bodybuilder and wanted to do something that would allow me to pursue my passion for bodybuilding while also earn enough money to one day support a family.  More specifically, I loved the synergy of resistance training and sports supplements and how each of these areas could enhance the body’s adaptations to training alone.

DDT: You are an Assistant Professor in the Exercise Science Program at the University of South Florida. Can you tell our readers a little bit about what your lab focuses on with research?

Bill: My laboratory – the Performance and Physique Enhancement Laboratory – focuses on improving performance and physique through resistance training and targeted supplementation and/or diet.  Specifically, we investigate different training programs and dietary supplements and their effects on improving performance variable such as maximal strength, power production, and muscular endurance.  Relative to physique enhancement, we investigate changes in lean body mass, body fat percentage, metabolism, and overall physique.


DDT: Can you give our readers a short description on the different types of studies (single blind, double blind, RCT, systematic reviews, etc) that are conducted in labs and what to look for when reading a peer-reviewed paper?

Bill: Relative to sports nutrition, the highest quality research designs are randomized, double-blinded, and placebo controlled.  Randomized means that the subjects are placed into either the treatment group or supplement group randomly, not based on any characteristic or performance measure that the subject may have.  A violation of randomization during the allocation of treatments is one area that can have tremendous impacts on the results of a study.  Double blinded means the participant does not know what they are ingesting (either the dietary supplement or the placebo) nor does the research staff know what the participants are ingesting (either the dietary supplement or the placebo).  Placebo controlled is basically giving a treatment (pill, tablet, beverage, etc.) that looks exactly the same as the real supplement, except that it does not contain any active ingredients.  The idea is to make every participant in a study believe that they are taking the ‘real thing’ so that they continue to train as hard as possible and are as motivated as possible.  As most of us are aware, there is something known as the ‘placebo effect’, which means that if someone takes a treatment (pill, tablet, beverage, etc.) that they think is the real treatment, even if it is a placebo in reality, the individual will experience similar outcomes as if they were taking the real treatment. That is why it is important to have a placebo in any well-designed sports nutrition supplement study.

When reading a sports nutrition research paper, the things that you want to look for are the population studied.  Ask yourself, is it a sedentary population?  A trained population? The population studied is very important in relation to the context of the applications that can be made from a particular study.  Even though a sedentary subject pool and a resistance trained subject pool are both human, the applications that can be drawn from these two populations are vastly different.  For example, one training program may prove to be very beneficial in a sedentary population, but may be ineffective in a trained population.  In summary, population matters and it is incumbent upon the reader to recognize the population being studied and to be cognizant of the applications that the authors are making.  A lot of people in our field tend to want to apply findings from a sedentary population to a trained population (or vice versa) – and this should be avoided.

Other things that I teach my students to look for when critically evaluating sports nutrition research papers is to notice the following:

Sample size – is it a small, medium, or large sample size?  If the sample size is small (generally speaking, less than 10 subjects per group), the study is biased to find no differences between the treatment and the placebo group.  If the sample size is moderate to large (generally speaking, more than 15 subjects per group), the study has appropriate power to detect actual differences between the treatment and the placebo, if one exists.  One of the biggest problems in our field is that many researchers and journals will publish studies with small sample sizes – this is a disservice to the profession and worse may lead many people to believe that a particular training program or dietary supplement may not be effective when in fact it may be, but the sample size was too small to detect such changes.

Setting.  Was the setting of the research study a ‘real world’ setting or a ‘laboratory’ setting.  Both settings have advantages and disadvantages, but it is essential that the reader be aware of the setting as they interpret the findings of published scientific articles.

Amount/Dosage.  This one is specific to sports nutrition studies.  It is important to notice the dosage used, how often, and whether the dosages were based on absolute amounts or were given relative to the subject’s bodyweight.  One of the unfortunate things in the sports nutrition industry is that some manufacturers will claim their products contain active ingredients of ‘supplement X’ or ‘supplement Y’, but the amounts of those supplements contained in the products is far less than what was shown to be effective in the scientific studies.


DDT: We heard your interview with Layne Norton and you discussed some research being conducted for physique competition with Dr. Smith-Ryan’s lab. Can you give us some insights on what that research is looking like and how it can help the physique competition industry?

Bill: The research in which I am assisting Dr. Smith-Ryan and her graduate student Eric Trexler is related to obtaining data at the time period of a bodybuilding/physique/bikini show.  For the past year, I had been collecting body composition and metabolic rate data on several competitive physique athletes, but Dr. Smith-Ryan’s study was the first study that I am aware of that is collecting this data in the context of a research study.  Specifically, what we are assessing is body composition, resting metabolic rate, specific salivary hormones (testosterone, ghrelin, leptin, insulin, and cortisol), and some questionnaires.  We are collecting this data in the few days prior to a competition, within several days following the competition, and then again about 6-weeks after the competition.  What we are specifically investigating is the extent to which fat mass is gained within 6-weeks following a competition, the extent to which resting metabolic rate is elevated after a competition, and any changes in the psychological and hormonal variables.  This will be one of the first studies in which this type of data is collected on a population of physique athletes at the actual time of their competitions.  I and my graduate students, Laurin Conlin and Nick Joy, are very happy to be a part of Dr. Smith-Ryan’s and Eric Trexler’s research team for this landmark study in physique athletes.

DDT: We’re going to switch gears here for a bit and talk about meal frequency and nutrient timing. We love the ISSN’s position stand on meal frequency. For those that haven’t read it, can you tell us your thoughts on what the data says about meal frequency?

Bill: Basically, the data that exists on meal frequency (the number of meals ingested per day) is not all that important in the sedentary population.  For example, there have been several studies in which 14 meals was compared against 3 meals per day, 6 meals vs. 3 meals, 3 meals vs. 1 meal, and 4 meals vs. 3 meals.  In each of these studies, in an untrained population, it was reported that there was no advantage to ingesting more meals as compared to fewer meals in relation to elevating metabolic rate or in maximizing fat loss.  This data is counter to what many of us believe – it was counter to what I believed and taught for many years – but the this data exists and it is very consistent.

There is an important point that we need to consider with this data, however.  None of the studies utilized resistance trained or exercising individuals in their populations.  So, to make the statement that meal frequency does not matter for those of us that are intensely training, that would be an incorrect extrapolation of the data.  What is more important, in my opinion, is the concept of protein timing in intensely training individuals. Unfortunately, this research has yet to be conducted, but if I were to hypothesize I think that ingesting high quality protein approximately 4 times per day will maximize training adaptations and lean body mass in a trained population.

Back to the data that we do have, if you are a sedentary individual or if you are a fitness professional one of your clients is a sedentary individual, we can safely say that it does not matter how many times this type of individual eats over a 24-hour period relative to fat loss and metabolic rate.  This allows a sedentary individual to eat as many meals as they feel comfortable eating, meaning that we do not need to alter their normal meal frequency intake or suggest that one meal frequency pattern is superior to another – the data simply does not support such a conclusion.


DDT: If we have 2 different subjects: Subject A is a high level bodybuilder/figure/bikini competitor and subject B is an average Joe just looking to look good naked. What would your suggestions be as far as meal frequency for each of these subjects? How would it differ?

Bill: My recommendations would be the same for both Subject A and Subject B – my focus would be on protein intake frequency (rather than meal frequency) and I would suggest about 4-5 “meals” of high quality protein per day (containing approximately 20 to 45 mg of leucine/kg body mass per meal).  The reasoning behind my recommendation is to maximize the muscle protein synthetic response at each meal.  It is also important to consider that protein ingestion influences more than muscle protein synthesis, it also elevates metabolic rate and enhances recovery from prior exercise.


DDT: Brad Schoenfeld, Alan Aragon, and James Krieger have a great meta-analysis on Protein Timing in the JISSN. Can you tell us your thoughts on what the data says about protein timing and overall nutrient timing?

Bill: I have noticed a trend in the scientific literature for many years that indicated that protein intake was not as important as I and others once thought relative to maximizing muscular strength.  Basically, maximizing muscular strength likely has more to do with neuromuscular attributes and less to do with increasing the size of the myosin heavy chain pool. This is not to say that muscle hypertrophy is not associated with increasing strength, but it is clearly secondary to improving neuromuscular efficiency in my opinion.  I do feel that total daily protein intake, including the timing of the protein, does influence the hypertrophic response to resistance exercise over a period of time.  I have read the meta-analysis by Schoenfeld, Aragon, and Kreiger, and I respect their work in this area very much, but I am not ready to embrace their findings as reported in their meta-analysis without reservation.  My opinion has been shaped by the fact that I am aware of only 2 studies that have used nutrient/protein timing as the actual intervention, and one of these studies reported that the timing of the nutrients was responsible for gains in lean body mass and the other study reported that the timing of the protein/nutrients had no impact on muscle hypertrophy. I think that there needs to be more work in this area, particularly with protein timing as the primary dependent variable before I state that protein timing is essential for enhancing lean body mass or come to the conclusion that it has no effect on lean body mass.


DDT: A common issue in the industry is protein intake. Can you tell us what an optimal intake of protein is and what the data says on daily protein intake?

Bill: I used to focus on the amount of daily protein intake, but the more I research this topic the more I believe the focus should be on the amount of protein ingested on a per meal basis.  Based on the research that I was able to find in humans, I believe the optimal amount of protein should provide about 20 to 45 mg of leucine/kg body mass per meal.  This recommendation comes from the research of Pasiakos et al. (2011) and Moore et al. (2009) (1, 2).  In order to make this work you must be aware of the leucine content of the protein source that you are ingesting.  As a general guide, beef, poultry, egg, casein, and fish are approximately 8-9% leucine and whey protein isolate is about 12% leucine.


DDT: What are some supplements that you recommend taking that have valid peer-reviewed research backing them up?

Bill: Not very many.  Creatine monohydrate, high quality protein sources (such as whey or casein), and caffeine in certain circumstance.  Other supplements that are good choices are a multivitamin (however, multivitamins will not enhance exercise performance) and high quality fish oil/EPA-DHA (similarly, fish oil will likely not improve performance, but may improve long term joint health).


Fun Time!

DDT: What is your favorite lift and why?

Bill: The Squat.  It is a whole body exercise which makes any time spent doing this lift an extremely efficient lift for time.  Also, the squat is probably the most functional exercise that can be done – it mimics the ‘athletic ready position’; it has application to the elderly who need lower body strength to get out of a seated position; and it is likely the best resistance exercise for elevating metabolic rate.

DDT: What are your current goals right now as far as training, physique development, etc? 

Bill: My current goal is to be able to deadlift over 400 pounds. A few months ago I was very close to this goal, but came up a little short.  I am very blessed to have some outstanding graduate students in my Exercise Science program that can assist me in achieving this goal.  Ryan Colquhoun and Danny Bove are both exceptional in their own expertise – Ryan Colquhoun with program design and Danny Bove with deadlift technique.  A few more months of working with them will have me reaching this specific strength goal.


DDT: Your favorite controlled-indulgence meal is______? 

Bill: Chocolate chip cookies and cold milk, but only if there are no more Buffalo wings available.  And lets not forget about pizza – I love pizza more than anything.


DDT: What does Dr. Campbell like to do for fun outside of the lab?

Bill: Doing absolutely nothing but laying around, watch football, spend time with my wife, teach my children about the Bible. I also love to simply talk about fitness, training programs, and how to improve performance and physique.


DDT: Where can our readers and supporters follow you and your work? 

Bill:  I am in the process of launching my website (  My team is hoping to go live with the website in June of 2015.  The website will serve those who want updates on the latest scientific research studies, findings from my research laboratory, and regular podcasts related to improving performance and physique.  Once the site is up and running, I will be sure to reach out to you guys so you can help spread the word!


DDT: Thanks for your time and knowledge Dr. Campbell!



Dr. Campbell is an Associate Professor of Exercise Science and the Director of the Performance & Physique Enhancement Laboratory at the University of South Florida. Dr. Campbell’s research is focused on improving exercise performance and enhancing physique through the synergism of resistance exercise and nutrition.  Dr. Campbell has published three books on sports nutrition, including the NSCA’s Guide to Sport and Exercise Nutrition and Sports Nutrition: Enhancing Athletic Performance.  Lastly, Dr. Campbell is a certified strength & conditioning specialist with the NSCA and is the current president of the International Society of Sports Nutrition.





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  1. Pasiakos, S.M., H.L. McClung, J.P. McClung, L.M. Margolis, N.E. Andersen, G.J. Cloutier, M.A. Pikosky, J.C. Rood, R.A. Fielding, and A.J. Young. 2011. Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis. Am J Clin Nutr 94(3):809-18.
  2. Moore, D.R., M.J. Robinson, J.L. Fry, J.E. Tang, E.I. Glover, S.B. Wilkinson, T. Prior, M.A. Tarnopolsky, and S.M. Phillips. 2009. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am J Clin Nutr 89(1):161-8.