Dietary protein quality lowers central abdominal fat

Dietary protein quality lowers central abdominal fat

The study examined the relationship between the amount of quality protein, carbohydrate and dietary fat consumed, as well as the number of time the 10g essential amino acid threshold was reached at a meal with central abdominal fat (CAF). Quality protein was defined as the proportion of protein intake comprised of essential amino acids. The 10g essential amino acid (EAA) threshold is based on previous research(2) showing that it maximally stimulates MPS while other research shows that an increase in essential amino acid provision above this threshold does not stimulate any greater muscle protein synthesis (MPS)(3).

 

The authors highlighted that consuming protein above the dietary reference intake (DRI) is associated with improved body composition(4) with proposed reasons behind this being increased muscle mass gains, increased thermogenesis due to the higher thermic effect of protein, and improved satiety among individuals consuming high protein intakes (5). Although previous research (6) showed that protein intake was inversely related to waist circumference, the quality of the protein source and its distribution through the day and correlation to CAF had not been investigated previously.

 

Methods

 

The study selected 27 subjects (12 men and 15 women) to take part in their cross sectional study. Subjects reported each week the amount of cardiovascular (174 ± 244 min) and weight training (93 ± 106 min) exercise they performed and EAA intake was determined from a 3 day food diary the subjects kept. The distribution of quality protein was determined based on the frequency with which the subjects reached the 10g EAA threshold in their meals.

A full body DXA scan was used to monitor body fat changes which give a high degree of accuracy compared to skinfold caliper tests.

 

Results

 

Mean values for dietary protein, EAAs, quality protein, and times reaching the EAA threshold have been previously reported (91g ± 45; 35.9g ± 19.5; 0.38 ± 0.02; and 1.4 ± 0.9 respectively) [7]. Mean values for carbohydrate and dietary fat intake were 235.3 ± 85.7g and 72.0 ± 28.6g respectively.

Quality protein intake consumed in the course of 24 hours was found to be inversely related to CAF while no associations were found with either carbohydrates or dietary fat consumption. The frequency with which the subjects hit the 10g EAA threshold was also found to be inversely related to CAF.

 

Conclusion

 

The study reiterated the fact that both provision of quality protein intake and the frequency of crossing the EAA threshold are inversely related to CAF. The researchers went on to say that as the majority of energy for ATP formation in muscle protein turnover comes from fat oxidation, a focus in maximising MPS by hitting the 10g EAA threshold could help increased resting energy expenditure from the oxidation of fat from increased lean mass.

 

Our Take

 

An interesting study without a doubt and one in the eye for those who think all protein is the same. This study highlights the fact that as much as protein intake is important we should look as athletes to provide the majority of our protein from sources rich in essential amino acids such as meats, fish, and dairy produce. By doing so, not only will we find it easier to hit the 10g EAA threshold associated with maximally stimulating muscle protein synthesis, but we also do so in the most efficient way possible without the need to ingest vast amounts of inferior protein to hit that threshold.

 

Previous research by Layne Norton (8) shows it is not enough to just continually provide an endless stream of EAA’s as the response of MPS to external EAA provision is estimated to last for two hours. Norton cites research which showed that even in the presence of a continuous infusion of essential amino acids for six hours, there was no further increase in MPS despite elevated plasma amino acid levels. This means that simply eating protein all day will not be an efficient strategy as there comes a point where we need to wait for the body to become sensitive to an influx of essential amino acids again. Rather than this, Norton suggests waiting 4-6 hours between meals and using an EAA or BCAA supplement to spike protein synthesis between meals.

 

Our view is that the important take home message from the research is that athletes need to place a priority on hitting the 10g EAA threshold at their meals which typically means meals of around 35-60g if eating meats and fish, with lower protein requirements of around 30g if eating dairy proteins such as whey. While there is no problem with eating more, it would be a poor meal indeed which fails to hit the 10g threshold. If your current diet means you have meals such as cereals for breakfast then you should look to either add some protein or amino acids to such meals to ensure you hit the 10g threshold for maximising MPS.

 

References

 

1. Jeremy P. Loenneke, Jacob M. Wilson, Anssi H. Manninen, Mandy E. Wray, Jeremy T. Barnes, and Thomas J. Pujol: Quality protein intake is inversely related with abdominal fat

2. Cuthbertson D, Smith K, Babraj J, Leese G, Waddell T, Atherton P, Wackerhage H, Taylor PM, Rennie MJ: Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. FASEB J 2005, 19:422-424.

3. Symons TB, Sheffield-Moore M, Wolfe RR, Paddon-Jones D: A moderate serving of high- quality protein maximally stimulates skeletal muscle protein synthesis in young and elderly subjects. J Am Diet Assoc 2009, 109:1582-1586.

4. Layman DK: Dietary Guidelines should reflect new understandings about adult protein needs. Nutr Metab (Lond) 2009, 6:12.

5. Halton TL, Hu FB: The effets of high protein diets on thermogenesis, satiety and weight loss: A critical review. J Am Coll Nutr 2004, 23:373-385.

6. Halkjaer J, Tjonneland A, Thomsen BL, Overvad K, Sorensen TI: Intake of macronutrients as predictors of 5-y changes in waist circumference. Am J Clin Nutr 2006, 84:789-797.

7. Loenneke JP, Balapur A, Thrower AD, Syler G, Timlin M, Pujol TJ: Short report: Relationship between quality protein, lean mass and bone health. Ann Nutr Metab 2010, 57:219-220.

8. Norton L: Optimal Protein Intake And Meal Frequency To Support Maximal Protein Synthesis and Muscle Mass

 

© 2012, Reggie Johal. All rights reserved.