Another day, and yet another scientific study breakdown.
Today I (briefly) bring you yet another study looking at the effects of higher protein intakes on body composition. And by higher intakes, I mean consuming protein at levels >3g/kg of bodyweight (1.3g/lb for those not metrically inclined). By most nutrition recommendations this FAR surpasses the requirements of virtually all individuals, be they sedentary (0.8g/kg) or highly trained (~1.7g/kg on average).
Today’s article is a follow up study to Antonio et al.’s 2014 paper  that looked at the effect of high protein intakes (~4.4g/kg), in conjunction with the subject’s normal resistance training routine (RT), on changes in body composition (i.e. fat mass [FM] and fat free mass [FFM]). What they found was that there were virtually no changes in either FM or FFM when consuming a high protein diet (4.4g/kg) for up to 8 weeks, again supporting the contention that excess protein is not converted to fat and stored as such in the human body. However, what Antonio and colleagues failed to do was prescribe an appropriate RT protocol that was standardized and assigned to each participant that ensured progressive overload; in other words constantly increasing the weight lifted and volume performed over the course of the 8-week study-period.
Enter today’s study: Antonio et al. 2014; A high protein diet (3.4g/kg) combined with a heavy resistance training program improves body composition in healthy trained men and women – a follow up investigation .
First the pros of this most recent paper:
- It addresses the dearth of research on high protein diets (>3g/kg or 1.36g/lb) in conjunction with a standardized, periodized resistance training program
- It uses already resistance-trained subjects (males and females), which eliminates any unusual gains that are typically seen in those who have never or rarely exercised before
- Randomization of subjects (ensures both groups are identical [in theory] from the start)
- BodPod for body composition (Siri equation; appropriate for study pop.)
- Again, training protocol (5 days/week for 8weeks)
– Adequate volume, intensity and frequency of movements (each body part 1-2x per week)
– Periodized (progressively increased weight lifted and volume performed)
Like all research there are methodological drawbacks:
- Tenuous control of dietary intakes (MyFitnessPal) that brings into question actual amounts of overall protein and calories consumed
- 34% dropout rate (very high)
- Average years spent training (5 years in HP group vs. 2.5 years in NP)
- No control for hydration status during BodPod measurements; however, hydration status less influential for BodPod measurements than DEXA
- Both groups gained 1.5kg FFM (on average; some wide variations between individuals).
- HP lost more BF (1.6 vs. 0.3kg) despite eating more kcals overall (~400kcals) than NP and being slightly leaner at the beginning of the study
– could potentially be explained by increases in NEAT and TEF in HP
– could be due to lack of accurate dietary recall/recordings
– better compliance of HP with RT protocol than NP group
- Both groups gained strength with progressive overload
- Blood work was normal for both groups, no adverse effects (for more on the safety of high protein diets see an article I’ve written here)
Protein intakes well above (i.e. 2-4x) RDA (0.8g/kg), in conjunction with periodized RT program that provides systematic progressive overload, can produce significant improvements in body composition (i.e. increase FFM, decrease FM and increase strength/performance). Moreover, and to the point of this article series, extra protein does not get stored as body fat. This is just another study refuting the idea that extra protein over the supposed RDA is converted to fat. While the pathways to convert amino acids to fatty acids DO EXIST, they are virtually irrelevant even in the face of excessively high protein intakes (like the ones seen in this study), especially when combined with a well-designed RT program meant to increase strength and muscle mass. Finally, it could be argued that protein intakes as high as, or even greater than, 3g/kg will not confer any additional benefits over ~2g/kg, as this was the intake seen in the NP group that saw near identical increases in FFM and strength. Thus, high protein diets ~2g/kg or higher can be a safe and valuable part of a structured RT program meant to increase muscle size and strength.
This article was contributed by Dylan Klein, the owner and Author of Calories in Context.
- Antonio J, Peacock CA, Ellerbroek A, Fromhoff B, Silver T: The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals. J Int Soc Sports Nutr 2014, 11:19.
- Antonio J, Ellerbroek A, Silver T, Orris S, Scheiner M, Gonzalez A, Peacock C: A high protein diet (3.4g/kg/d) combined with a heavy resistance training program improves body composition in healthy trained men and women – a follow-up investigation. Journal of the International Society of Sports Nutrition2015, 12:39.