BCAA supplementation not beneficial for lean mass preservation, insulin sensitivity in obese adults – Singapore RCT

The researchers conducted a 16-week RCT comparing 1) a standard protein low calorie diet with BCAAs supplementation Vs 2) one with placebo and 3) a high protein diet with placebo.

The aimed to find out if BCAA supplementation could improve lean mass preservation, including muscle mass, bones, and bodily fluid, except body fat, and insulin sensitivity in obese subjects undergoing weight loss. 

This is based on the existing understanding that BCAAs, such as leucine, isoleucine, and valine, could improve insulin sensitivity and develop muscle mass/prevent protein loss in conditions characterised by muscle protein wasting. 

Writing  in The Journal of Nutrition, ​however, the researchers from the National University of Singapore, A*STAR, and several local hospitals, found that a high protein diet was more effective than a standard protein diet with BCAA supplementation in lean mass preservation.

Nonetheless, a standard protein diet with BCAA supplementation still performed better in this area as compared to one without BCAA supplementation.  

“This suggests that while BCAAs may aid in lean mass preservation, they are not comparable to higher absolute amounts of protein, which may have the enrichment of other nutrients like calcium, bioactive peptides, B vitamins, zinc, and fatty acids that can possibly benefit lean mass retention,” ​the researchers said.

The MRI results also showed that BCAA supplementation could increase calf muscle volume.

“The significant increase in calf muscle volume with BCAA-supplemented standard-protein diet is interesting and novel but the practical significance of this increase in calf muscle volume may be negligible.”​

A total of 132 men and women took part in the study.

More than half had body mass index (BMI) between 25 and 30, while the others were between 30 and 35.  

They were randomised to receive either 1) a standard-protein hypocaloric diet with BCAA or 2) a standard-protein hypocaloric diet with placebo or 3) a high protein hypocaloric diet with placebo.

The standard-protein diet provided protein at 14 percent of the total energy, while the high-protein diet provided protein at 27 percent of the total energy.

The BCAA supplement, a tablet, contains 325mg of L-leucine, 162.5mg of L-isoleucine, and 162.5mg of L-valine.

After the 16 weeks were over, they underwent an eight-week weight maintenance phase where the BCAA supplement or control is given, but without the protein diet.

Insulin sensitivity  ​

All three groups showed an improvement in insulin sensitivity after the 16-week dietary intervention. However, there was no significant difference between the three groups.

Moreover, blood glucose, insulin, and insulin sensitivity returned to baseline levels after the eight-week weight maintenance phase.

This suggests that a hypocaloric diet and weight loss may be the main factor in regulating glucose homeostasis and insulin sensitivity, the researchers said.

This is in contrast to some of the existing studies which showed that BCAA supplementation could reduce insulin resistance.

Carb Vs protein ​

Another finding is that a high protein intake may not lead to greater body weight loss, as reducing carbohydrate intake alone would be sufficient.

Similar weight loss was observed in all three groups and the common factor between them was a hypocaloric diet.

“Our study demonstrated that hypocaloric diets with standard or high protein content, in combination with either BCAA or placebo supplementation, were equally effective in reducing body weight, body fat mass, and waist circumference after 16 week of weight loss intervention.”​

This means that “reducing the amount of energy intake alone through hypocaloric diet is sufficient to induce weight loss and an additional increase of protein intake may not induce a greater loss in body weight,” ​the researchers said.

In addition, there was an improvement in the lipid profile for all three groups after the 16-week dietary intervention, but this was not the case after the eight-week weight maintenance phase.

This shows that a hypocaloric diet induced weight loss was sufficient in causing a change in the lipid profile.

“In conclusion, a supervised hypocaloric diet is effective in short-term weight loss, with evidence of weight maintenance. ​

“BCAA supplementation to a hypocaloric standard-protein diet caused higher distal muscle volume preservation but did not have a significant effect on the magnitude of weight loss or maintenance of weight loss, lean mass preservation, and changes to insulin sensitivity and metabolic profile.​

“In summary, it may be more advantageous to consumer a high protein diet instead of taking a BCAA supplement when on a hypocaloric weight loss diet,”​ the researchers concluded.  

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Source: The Journal of Nutrition ​

Branched-Chain Amino Acid Supplementation Does Not Preserve Lean Mass or Affect Metabolic Profile in Adults with Overweight or Obesity in a Randomized Controlled Weight Loss Intervention​

https://doi.org/10.1093/jn/nxaa414​

Authors: Mary F F Chong and et al​