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Rethinking Optimal Protein Intake

Protein has always been the hot topic in sport nutrition. It seems to be the cornerstone upon which bodybuilders build the other macronutrients. Bodybuilders want to know how much to take, when to take it, the best sources to take, and much more. I have heard so many times the recommendation that bodybuilders should consume 1g of protein per pound of body weight. Do you ever wonder where this number originated? I think it is time to readdress the age-old question of how much protein should we consume per day.

What I want to tackle here is how much protein we need to optimize body composition for bodybuilding. “Optimize" is the key word, which can be misconstrued with what is needed. A “need” might be considered a minimalist approach. We are not trying to just take in what is needed to get the minimum response; we want what will maximize body composition to the fullest. I think it would be pertinent to mention that protein is considered the “adaptive nutrient.” It’s the nutrient that can cause an adaptive response to build muscle and change the physique. This is why we should discuss protein needs more often in terms of what is optimal.

Current Recommendations

Most research in protein clearly shows there is an increased need for the bodybuilder. The 2017 ISSN Position Stand on protein recommends 1.4-2.0g/kg for building and maintaining muscle mass.1 They also add that if an athlete is in a hypocaloric state the intake should increase to 2.3-3.1g/kg per day. Several of the studies in the ISSN review paper conclude that around 2.0g/kg will maximize protein synthesis—converted to pounds and rounded up, that number falls pretty closely to the commonly recommended 1g/lb of body weight for protein. A more recent systematic review by Morton et al. addressed the question of protein intake in resistance training. The researchers reviewed 49 studies and found that intakes of 1.62g/kg resulted in no further fat free mass gains.2 This is also looking at the amount of protein that maxes out protein synthesis. No studies investigated going over 3g/kg of protein, a common practice by bodybuilders. Now, you really have to understand what is being measured and looked at in these studies. Some studies are looking at nitrogen balance, amino acid uptake, and muscle protein synthesis.

Not only are there inherent limitations to these methods, but looking at an individual piece of skeletal muscle physiology is a narrow view of how protein works in a system. As bodybuilders we want to know what will improve body composition, not what will only influence one metabolic pathway. Protein is used by organs, the immune system, connective tissue, and other pathways that we have not have yet identified. We can also look more critically at what really affects protein needs. Were subjects untrained or trained? A trained subject is potentially more adapted to utilizing protein and wouldn’t require as much. Was resistance training in the program periodized? If the program is suboptimal, a higher protein intake might not be needed. Age can affect protein intake as increasing age diminishes the response to protein. How long was the duration of the study? Most studies are less than 16 weeks to accommodate school semesters.

Lockwood et al. set out to compare the effect of different whey protein forms (hydrolysate and concentrate) vs. placebo on body composition and strength.3 They split 68 males into three groups and resistance trained them for 8 weeks. The whey hydrolysate, whey concentrate, and placebo group had total daily protein intakes of 1.9, 1.91, and 1.58 g/kg respectively. Lo and behold, there was no change in muscle mass or strength between groups. Well there you go—we are back at the 1.6g/kg not giving you more muscle mass. What was interesting was the whey hydrolysate group lost more body fat, but experienced the same muscle building. Now we are talking about body composition and not just a single muscle physiological pathway. Let’s look at some research that goes way beyond the 1g/lb of protein recommendation.

Enter the High Protein Zone

In most of the studies above, it is rare to see protein levels compared over 3g/kg for protein. 1.6-2.0g/kg has been recommended for maximizing fat free mass and muscle building ability, but looking at body composition changes above this protein range is rare. Antonio et al. conducted several studies with protein levels as high as 2g/lb of bodyweight. In 2014, an 8 week study was conducted with well-trained subjects.4 Subjects were divided into two groups: 1.8g/kg vs. 4.4g/kg protein. The study resulted in no change in training volume, body weight, fat mass, fat free mass, or percent body fat between groups. Interestingly, the 4.4g/kg group consumed on average an extra 800 calories per day for the 8 weeks yet maintained the same body composition as the group with lower calories. This really makes you wonder if a calorie truly isn’t a calorie.

This led Antonio on to his next study in 2015 that compared 2.3g/kg vs. 3.4g/kg in 48 well trained subjects.5 The protein was lowered from 4.4g/kg in the previous study as there were complaints about the sheer volume the subjects had to eat. The subjects were put on a periodized split routine for the 8-week period. The 3.4g/kg group lost an average of 1.6kg of body fat mass (2.4% body fat) vs. the 2.3g/kg group losing 0.3kg (0.6% body fat) body fat mass. The high protein group also consumed more calories than the low protein group (2614 vs. 2119 calories respectively). Fat free mass gain was the same between groups. A diet higher in protein and calories led to the same fat free mass gains but a reduction in body fat. Although 1.6-2.0g/kg protein amount will maximize muscle protein synthesis, there is evidence that going even higher to 3.4g/kg or even 4.4g/kg could allow high calorie intake and decrease in fat mass. How is this even possible? We don’t have research to explain the mechanisms behind the fat reduction, but Antonio et al. hypothesized that the higher thermic effect of food might have been at work. Protein just takes more calories to digest. There was possibly an increase in Non-Exercise Activity Thermogenesis (NEAT) due to the subjects being more active.

Now let’s look at the misconception that high protein is bad for our kidneys and bones. Antonio et al. conducted a case study for 2 years on 5 well trained male bodybuilders and monitored liver and kidney function.6 Protein intakes on average were 3.2g/kg in the first year and 3.5g/kg in the second year of the study. They found no abnormal liver or kidney function. Antonio et al. investigated bone health in women and followed two groups of women for 6 months.7 There was no change in bone mineral density or bone mass between the group that consumed 1.5g/kg vs. the group that consumed 2.8g/kg. Protein amounts at around the 3g/kg mark are safe on kidneys and bones in healthy subjects.

Conclusion

We don’t know how much protein is needed to optimize all the physiological pathways affected by protein. We have studies that show up to 3.4g/kg of body weight is not harmful but has potential benefits in improving body fat levels and will maximize muscle protein synthesis as well. If maximizing body composition is your goal as a bodybuilder, I see no reason why we can’t set the minimal optimal level at 3.4g/kg (1.5g/lb) of body weight. The only caveat I would make on this is if this amount of protein reduces the amount of carbohydrates and fats enough to impede performance. Further research is needed to investigate high levels of protein intake and mechanisms for fat loss.

References

1. Jager R et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017 Jun 20;14:20.
2. Morton RW et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018 Mar;52(6):376-384.
3. Lockwood et al. Effects of Hydrolyzed Whey versus Other Whey Protein Supplements on the Physiological Response to 8 weeks of Resistance Exercise in College-Aged Males. J Amer College Nutri. 2016 Oct; 36(1):1-12.
4. Antonio et al. The effects of consuming a high protein diet 4.4g/kg/d on body composition in resistance-trained individuals. J int Soc Sports Nutr. 2014; 11:19.
5. Antonio et al. A high protein diet (3.4g/kg/d) combined with heavy resistance training program improves body composition in healthy trained men and women- a follow up investigation. J Int Soc Sports Nutri. 2015; 12:39.
6. Antonio et al. Case Reports on Well-Trained Bodybuilders: Two Years on a High Protein Diet. J Exer Phys Online. 2018 Jan; 21(1):14-24
7. Antonio, J., et al., High protein consumption in trained women: bad to the bone? Journal of the International Society of Sports Nutrition, 2018. 15(1):6.

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