5 questions with Bill Campbell, Ph.D. about strategic dieting for female physique competitors and bodybuilders


Interviewer Mike Roberts, Ph.D.: Bill, I have to first thank you because you got me into research when I was at Baylor University circa 2003.  It’s been great to see you doing high-impact research in the bodybuilding realm, especially with female athletes.

Dr. Bill Campbell
Bill Campbell, Ph.D., Director of the Performance & Physique Enhancement Laboratory at the University of South Florida.

BC: Yes, I still remember the first time we met. I remember you telling me that you walked on the Baylor Football team the past year and you were explaining your basic science courses and how much you liked exercise physiology.

If my memory serves me correctly, I told you about the lab that I was a research assistant in (Exercise and Sport Nutrition Lab) and I think at that point you came to visit the lab and loved it.  Fast forward a year and you were the grad student that all the other graduate students would reach out to with all of our toughest physiology questions!  And I have some more questions for you today!

Q1: While training is important, physique competing is a largely a sport of dieting.  Without getting too in-depth, can you give us insight in terms of how athletes structure their diets to gain muscle mass and then trim up for the stage?

BC: For a natural physique athlete, they basically live in two different body composition goals: gaining muscle and losing fat. A long time of their non-dieting phase (called the off-season) is devoted to accumulating as much muscle as possible (the gaining muscle phase). This is done with CONSISTENT resistance training and relatively higher calories, making sure that protein intake is adequate (no less than 1.6 grams/kg body weight).

Generally, cardiovascular exercise is either not conducted during this time or if it is done minimally. Once a physique athlete identifies a show they want to compete in, they spend the next ~16 to 32 weeks dieting down to lose fat (but also doing everything they can to maintain all of the muscle that they spent so much time trying to accumulate over the past several months or years). 

During this fat loss phase (referred to as contest dieting), two main things happen: 1) Calories are decreased and 2) physical activity is increased. This is where many physique athletes will start doing some type of cardiovascular exercise.  In terms of diet, the consistent theme that I see is that carbohydrates are lowered more than fat, and protein intake is either maintained or even increased during this time.

Q2: Dietary protein needs for physique competitors is always a hot topic. Your laboratory recently published data on the effects of a lower versus higher protein diet in aspiring female physique athletes. Can you provide the high points of that study?

BC: We took aspiring female physique athletes (the majority of whom planned to do a physique competition in the next year) and randomly assigned them to ingest a lot of protein (2.5g/kg) or a limited amount of protein (0.9g/kg) while they resistance trained for 8 weeks in my Performance and Physique Enhancement Laboratory).

We instructed them to not change anything about their carbohydrate and fat intakes, the only thing we wanted them to change was the amount of protein they were consuming for 8 weeks.  We trained every subject on how to track their macros, each subject was provided a personal nutrition coach, and because of this investment we were able have each subject track every gram of food that entered their mouth every day for 8 weeks.

At the end of the study, the high protein group gained significantly more lean muscle mass than the low protein group (2.1 vs. 0.6 kg of muscle).  Another very interesting finding that we observed was that the high protein group actually lost a significant amount of fat mass (-1.1 kg) despite increasing their total caloric intake by 250 calories per day (all excess calories were from protein)! 

While this may sound like a crazy outcome, this is now the fourth study that has reported similar outcomes.  Perhaps you and your students are aware of the most recent study that also reported that an increase in protein intake resulted in a significant loss of body fat (without reducing caloric intake) that was conducted by you and others at Auburn University: Effect of Whey Protein Supplementation on Physical Performance and Body Composition in Army Initial Entry Training Soldiers.

Q3: I recently saw a graduate student who worked with your group give a nice presentation on the “re-feed” option during dieting. Can you explain the mechanics of the “re-feed” strategy, and how physique competitors could implement it into their pre-competition cutting phase?

The idea with a re-feed strategy is to protect against adaptive thermogenesis that occurs with dieting. Adaptive thermogenesis is a term that describes how your body responds to calorie restriction. The body’s natural tendency is to slow down metabolic rate, which makes it harder and harder to continue to lose weight/fat without further reducing caloric intake. 

What we did with our re-feed strategy was to have resistance-training males and females diet for 5 straight days but then disrupt this dieting by increasing calories for 2 straight days. This cycle was repeated for 7 straight weeks and the re-feed group was compared against another dieting group that did not incorporate weekly re-feeds (they just dieted every day for 7 straight weeks).  At the end of the 7-week study, we observed that the re-feed group was better able to maintain metabolic rate and muscle mass as compared to the group that did not periodically increase caloric intake.

Q4: A lot of recent attention has centered around the negative consequences of yo-yo dieting or crash-and-burn dieting. So, what are possible ways for female or male competitors to avoid this pitfall after competitions?

The best way to avoid this pitfall is to have a somewhat controlled post-competition weight re-gain strategy.  There are currently two popular approaches to doing this: a reverse diet strategy and a recovery diet strategy.

A reverse diet strategy is a very slow re-introduction of calories back into the diet after a competition. A recovery diet strategy more rapidly introduces calories back into the diet after a show, but it is still controlled and monitored.

One of my master’s students, Jaymes Longstrom, is investigating these post-competition dietary strategies right now in a case-study series approach.  He is monitoring about 10 physique athletes as they follow either a reverse diet or a recovery diet for up to 8-weeks post competition.

Q5: What are some future research areas that you’re exploring?

My graduate student, Madelin Siedler, will be coordinating a study on diet breaks in resistance trained females next year. This study will compare several weeks of continuous dieting vs. intermittent dieting (3 weeks of dieting and then a week of maintenance calories). This is going to be a nice follow up to our diet re-feed study that we completed this past year. 

Another graduate student of mine, Megan Humphries, is coordinating a study that will compare the recovery abilities of males vs. females following a resistance exercise bout. It has always been my observation in my own workouts (when I do squats with my wife she is ready to do her next set in a minute or two and I am literally sprawled out on the gym floor gasping for breath) that I do not recover from set to set like my wife does. 

I have also noticed this general trend in females—they recover faster than males. For this study, Megan will be investigating the time course of recovery (4 hours, 24 hours, or 48 hours) from upper body and lower body exercises as well as the intra-workout (set to set) recovery.

Very interesting! Thanks so much for your time today, Dr. Campbell.

BC: While I have the ‘microphone’, I would like to share a few thoughts with your current or future students at Auburn.  I don’t know if your current students appreciate this or not, but what you and your colleagues have accomplished the past few years at Auburn is incredible.

Your students are literally in one of the best (if not the top) kinesiology programs in the nation for learning opportunities. They can engage in applied science (similar to what I do) such as investigating and learning about the effects of protein supplementation on body composition or performance; or they can direct their learning opportunities at the cellular level and learn about the muscle transcriptome; and finally, they can even forego the human species and choose to investigate animal and cell culture models.

I trust that your students are appreciative of this fact because it is so rare to have opportunities like these that are applied towards the fun things that we all like (getting in better shape, losing fat, lifting more weight, being more powerful, etc.).

And in closing, I would like to make a shout out to Carl Fox (a former master’s student of mine and current doctoral student in your program).  Carl is one of the hardest working, most dependable, and holds the all-time record for having a positive attitude for the most days in a row (even on the rare day when the Auburn football team lost a game). I hope to be able to have more of my best master’s students follow the footsteps of Carl and have the opportunity to continue their education in the School of Kinesiology at Auburn University. 

Dr. Bill Campbell is an Associate Professor of Exercise Science and the Director of the Performance & Physique Enhancement Laboratory at the University of South Florida.  

To find out more about Dr. Campbell’s research, check out:

Website: Performance & Physique Enhancement Lab

 Instagram: @billcampbellphd

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