Full paper: Restoration of metabolic health by decreased consumption of BCAAs (2017)
Paper Summary
This study initially fed rats 2 diets for 12 weeks: control diet (regular chow), or a Western diet (WD) - similar macronutrient ratio to a high-sugar, high-fat Western diet, which is well known to induce obesity in rats[1] . While the rats fed the control diet maintained a normal weight during the 12 weeks, the rats fed the WD became obese. In the second part of the study, that lasted 14 weeks, the control group continued eating their control diet, while the WD group was divided 5 different diets, as can be seen here. Both reduction of all protein content (WD -> ExLow AA) and reduction of only BCAAs (WD -> ExLow BCAA) have resulted in rapid weight loss, compared to the group changed from WD to the control diet. BCAA and protein restricted rats also had significant improvements in glucose tolerance and insulin sensitivity.
The more striking thing was, that in the third part of the study, it was also found BCAA restriction protects against the obesogenic (obesity-producing) effects of the WD. In this part, the obese rats still lost weight rapidly despite eating a diet that normally produces obesity.
BCAA- and protein-restricted rats also had a higher lean-to-fat mass ratio than rats fed the obesogenic WD diet, indicating greater loss of fat mass rather than lean mass during BCAA/protein restriction.
BCAA- and protein-restricted rats also had higher energy expenditure (burned more calories), due to higher FGF21 levels. FGF21, in addition to increasing energy expenditure, also increases insulin sensitivity and inhibits the mTOR & IGF-1 pathways[2][3] .
Possible Mechanisms
Cell growth is governed by many pathways, a central one being the mTOR pathway - a nutrient sensing pathway. When mTOR is activated, it signals cells to survive and grow. The mTOR pathway is mostly activated by amino acids - insulin can also activate it, but not without amino acids. Overactivation of mTOR is implicated in insulin resistance[4] and obesity[5] . The mTOR pathway mostly senses amino acids, and it specifically senses BCAAs more than all other amino acids. Therefore, a diet low in BCAAs reduces mTOR activation significantly, and this can have positive effects on markers of obesity, such as acceleration of fat loss and improvement of insulin sensitivity. However, mTOR activation is also required for muscle growth, so a low BCAA diet could slow down muscle growth significantly.
FGF21, a hormone-like signalling molecule, which is increased significantly by BCAA or protein restriction, has anti-obesity and anti-diabetic effects, due to it increasing energy expenditure. In addition, it has inhibitory action on the mTOR & IGF-1 pathways, which might further contribute to its positive metabolic effects.
Discussion
Weight loss diets in humans commonly focus on the ratio of fat to carbohydrate, without highly regarding protein ratio of the total caloric intake. Ketogenic diets are anecdotally said to improve weight loss, and this is often attributed to their low-carbohydrate content. However, ketogenic diets are also protein-restricted, since overconsuming protein activates gluconeogenesis (glucose synthesis in the liver), and thus abolishes ketosis. Therefore, it is possible that the weight loss induced by ketogenic diets is more strongly related to protein restriction, than it is to carbohydrate restriction.
One study in humans (from 2016) did show BCAA restriction (7-9% protein diet) for an average of 43 days, induces weight loss without caloric restriction in overweight and mildly obese males (n=38), but more data is needed - studies with female participants, more total participants and for longer time periods would be required for a better view of the possible short- and long-term effects of BCAA/protein restriction.
Conclusion
BCAA restriction might be a promising avenue for accelerating weight loss and improving insulin sensitivity in humans.
[link] [comments]
from loseit - Lose the Fat https://ift.tt/2Nrc9dS
No comments:
Post a Comment