For years, I have searched the literature and the food practices around the world for information that would help explain disparate (but rising almost everywhere) obesity rates. Repeatedly, the information pointed at fermented and cultured foods in traditional diets as being extremely important in maintaining a healthy weight, but when I attempted to apply that information to my own diet, the results were inconsistent and disappointing.
During the last two years, I did obtain good results using some kombu seaweed and an obscure brand of brewer's yeast that I only bought once--both items are remarkable for their high glutamic acid content. I was not able to obtain and use the exact same items again, though. Kombu that I have bought more recently doesn't even taste the same, and a more famous brand name of brewer's yeast doesn't give the same rapid weight-loss result as I experienced from the first brand.
I was surprised to read in our enormous old dictionary last week--it's a third edition Merriam-Webster dictionary that outweighs some toddlers--that glutamic acid has three optically isomeric forms. According to every online resource I have read, amino acids have up to 2 optical isomers. That failure to acknowledge a third optical isomer in modern resources appears to be intentionally deceptive and goes far to explain why it has been so difficult to solve the global weight crisis. Glutamic acid is formed during fermentation, and with chlorination, irradiation, and preprepared bacteria/yeast packets pervading modern food manufacturing, it is likely that we have allowed the means of producing a crucial isomer of glutamic acid to be nearly completely excluded from our food supply.
Why is glutamic acid so crucial to weight loss? It can be changed by transaminase enyzmes to alpha-ketoglutaric acid and alanine (which, according to my dictionary, also has three optical isomers). Whether this transformation takes place can be affected by which of the three optical isomers of glutamic acid interacts with the transaminase enzymes.
Alpha-ketoglutarate has been shown to increase beige fat (the good kind of fat cells, which unfortunately we tend to make less of as we age) and alleviate obesity caused by a high fat diet in mice (see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6974731/). Giving obese rats alpha-ketoglutarate reduces "the weights of white adipose tissues, thereby improving metabolic profiles and whole-body insulin sensitivity (indicated by oral glucose tolerance test) in diet-induced obese rats" (see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6775570/).
There are many studies in rats and mice that don't carry over to humans, so why should I think alpha-ketoglutarate is important to human weight loss? The intriguing characteristics of intestinal absorption of alpha-ketoglutarate--significantly better absorbed in the proximal sections of the small intestine, with higher absorption where there is low pH, Fe(2+) and/or SO ions (see https://pubmed.ncbi.nlm.nih.gov/16401194/)--immediately call to mind the physical effects of roux-en-y gastric bypass surgery. Roux-en-y bypass causes food to entirely skip going through the first part of the small intestine, and it increases the pH of the small intestine ("Median pH was high in patients with RYGB during the first hour of the oro-cecal segment (6.45 ± 0.4 vs 3.65 ± 1.55 pH units for healthy controls; P < 0.001), as well as during the entire oro-cecal segment (6.97 ± 0.4 vs 5.51 ± 1.1 pH units; P < 0.001)." https://link.springer.com/article/10.1007/s11695-021-05308-x) It appears plausible that roux-en-y bypass surgery is more effective than other kinds of gastric bypass and a wide variety of calorie restriction efforts precisely because it prevents absorption of alpha-ketoglutarate in the duodenum and upper small intestine.
