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Diet+Resistance Training+Protein=X

Posted on May 6th, 2009 by Matt Schoeneberger

Let’s talk research.

One of the studies we reviewed for S.P.E.E.D.’s exercise chapter compared the effects on body composition and strength gain of a calorie-restricted diet with or without resistance training, differing levels of protein intake and different types of protein supplementation over 12 weeks.  Participants were randomized into three groups:

-Diet alone

-Resistance exercise +whey protein

-Resistance exercise + casein protein

The results of the study showed support for the benefits of protein intake (25% of total calorie intake vs. 16% in diet alone group) and resistance training on body composition, since both groups showed increased fat loss and increased muscle gain compared to the diet only group.  Additionally, the casein group showed significant increases in both measure when compared to the whey group.  The same goes for strength gain – the casein group comes out on top.

There are some issues with the design of the study we’d like to discuss.  This will give you a window into what we are doing as authors when writing the book, so you can understand what goes into well-supported advice.

First, when discussing the grouping of participants, the authors mention that the diet only group was assured they could follow the full program after the 12 week research period.  Well, isn’t that a bit de-motivating, knowing that you’re not getting the full program?  This is where blinding of research comes into play.  The diet group shouldn’t have known that there was even an alternative to their treatment, that there were two other groups who got to perform resistance training programs.  This could greatly affect the diet-only group’s ability or willingness to comply with the program.

Second, speaking of resistance training programs, the authors of this study do not specify the resistance training programs that were followed by the two protein+exercise groups.  We find out that they performed 4 exercise sessions per week, working one of four large muscle group each session, and the session took 30-35 minutes.  There is no mention of whether or not the exercise sessions were the same for each group outside of these parameters.  What if one group performed 1 set of 10 reps while the other group performed 4 sets of 10 reps?  Would we not expect a difference between groups?  A researcher cannot be too specific.

The differences between the two protein+exercise groups in body composition changes and strength changes is remarkable.  The casein group took their bodyfat % from about 26 to about 18.  The whey group changed theirs from 27 to 23.  The casein group increased total strength by 59% while the whey group increased by 28%.  These are staggering differences over a 12-week period!

One thing we noticed while looking over the study was the mention of the sources of protein supplements.  The whey supplement by one manufacturer and the casein supplement by another.  There is no mention of any conflicts of interest of the authors or any mention of sponsorship by any corporation.  We can only hope that the researchers did not skew the results of the study, knowingly or unknowingly, toward one product being used.  This could be a case of conformation bias – what happens when a researcher has an ideal conclusion in mind and so steers the research toward that conclusion or outcome.

Blinding a study, which refers to the act of making sure the researchers and/or participants are completely unaware to which group they belong, can greatly reduce this phenomenon, but is not mentioned in this study.  For example, if the researcher who takes the body composition measurements does not know which participants belong to which group, the researcher has no reason to skew results.  However, if this information is known by the researcher performing the measurements, skewing the results, both consciously or unconsciously, is  a possibility and cannot be ruled out.

In conclusion, since a practitioner should never base their methods of practice off of one single source of research, this study needs to be combined with many others to decide whether or not resistance training, caloric restriction, and protein supplementation are beneficial when making body composition changes.  Wouldn’t it be nice if  someone was working on compiling all that information right now and putting it in an easy-to-read, easy-to-follow plan?  Hmmm…. what a good idea :)   Check out our weight loss ebook as soon as it’s available!

Demling RH, DeSanti L. Effect of a hypocaloric diet, increased protein intake and resistance training on lean mass gains and fat mass loss in overweight police officers. Ann Nutr Metab. 2000;44(1):21-29.

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