Fat Burning Silk Peptides From Korean Labs: You Don't Even Have to Eat Worms to Gear Your Personal Energy-In-VS-Energy-Out Equation Towards Weight & Fat Loss

It does resemble a birds nest but what you see here are silk proteins not swallow eggs and birds poop.
Let's first get two things out of the way: Yes this is yet again a rodent study and no, it has not been sponsored by BPI, who are trying to tell you that you should buy their silk protein based supplement instead of any other amino acid product if you want to get bigger, leaner, faster and... well, they don't say that, but obviously also poorer.

Now that we have got the sarcastic introduction out of the way, let's get back to the facts the study at hand is not the first to describe beneficial effects that may be brought about by the consumption of silk peptides.

Silk the traditional protein base fat burner from the far East?

What may sound gross to some of you, does in fact have a longstanding tradition in the Asian countries and has already been shown to suppress adipogenesis in preadipocytes of rodents on high fat diets by Lee et al. in 2012.
The mashes that are used to cover up hernias could soon be made of silk, as well.
Silk as tissue substitute: To be honest, the effects silk proteins could have on your belly, are actually not the really exciting stuff about silk. While it is not the silk of the common silkworm, but the stronger silk variety of spiders, the latter may in fact soon replace conventional materials that are currently used to manufacture "implants" like the meshes that are used to fix hernias (Schäfer-Nolte. 2013). They are more stable than most of the conventional materials and, more importantly, are not identified as a "foreign" object and thus not attacked by our own immune system.

Scientists from the Tufts University and other renowned research facilities are also developing new silk-based delivery devices for drugs (Pritchard. 2010).
The results of the most recent study from Korea (Kim. 2013), on the other hand, render a supplement that has hitherto been investigated mainly as an anti-diabesity interesting for physique athletes and gymrats, as well. The researchers from the Konkuk University used an open-circuit calorimetry system to measure the energy expenditure of mice that received either 800mg/kg of silk peptides of placebo or 2 weeks and had to exercise on a treadmill for 50 minutes five times a week (20m/min in week 1, 25m/ming in week 2).
Figure 1: Fat oxidation in control and silk peptide group at the end of the study period (Kim. 2013)
As you can see in figure 1, the mice in the active arm of the study had a higher total oxygen consumptions, a higher fat oxidation and correspondingly lower respirator exchange ratios (indicating a higher contribution of fat to the energy expenditure).
Figure 2: The 66% reduction in food efficiency does basically mean the rodents hat to eat 3x more to gain the same amount of body weight, the high isoleucine content in the silk peptides should remind you of a previous SuppVersity article on the beneficial effects of isoleucine containing peptides in whey hydrolysates (read more)
The combination of exercise and silk protein also led to a statistically significantly lower body weight gain and a 66% reduction in feed efficacy. In other words: Despite eating much more, the mice with the silk protein in their diets gained significantly less body weight.

Read my past elaborations on silk proteins, when BPI first announced their new "BLOX" silk protein supplement (read the whole article)
Bottom line: As a standalone study the latest results from Korea are interesting, but not impressive. In conjunction with the results from previous studies, where Shin et al. (2010) observed direct ergogenic effects in an exhaustive exercise scenario, the anti-diabetic effects of respective hydrolysates (Do. 2012) , its ability to increase GLUT-4 activity and thus facilitate glucose uptake (Lee. 2011), it would be impressive, if we had (a) human data to prove that you me and every of our non-hairy cousins would see similar results; and (b) if silk protein would stand the test against another source of small peptides... which one? Well what about plain hydro-whey (WPH)? You've read about WPH's ability to improve blood glucose management, as well as its antioxidant effects before. So until this data is available, it may be worth to keep silk on the radar, but would be an N=1 experiment with an undetermined chance of success if you bought it.

Speaking of whey hydrolysates: If your goal is to build mass and lose body fat the similarity of silk proteins to whey hydrolysates may, in fact be another reason not to literally buy into the hype (which has by the way already abated ;-) Why?  Well you must have missed Tuesday's post "Is hydrolized Whey, the New Way to Go? 12 Week Human Study Suggests: Yes, If Your Goal is to Ward Off Oxidative Damage. No, If You Want to Build Muscle & Lose Fat" (read more) otherwise you wouldn't be asking.

  • Do SG, Park JH, Nam H, Kim JB, Lee JY, Oh YS, Suh JG. Silk fibroin hydrolysate exerts an anti-diabetic effect by increasing pancreatic β cell mass in C57BL/KsJ-db/db mice. J Vet Sci. 2012 Dec;13(4):339-44.
  • Kim J, Hwang H, Yun HY, Kim B, Lee CH, Suh H, Lim K. Silk Peptide intake increases fat oxidation at rest in exercised mice. J Nutr Sci Vitaminol (Tokyo). 2013;59(3):250-5.
  • Lee HS, Lee HJ, Suh HJ. Silk protein hydrolysate increases glucose uptake through up-regulation of GLUT 4 and reduces the expression of leptin in 3T3-L1 fibroblast. Nutr Res. 2011 Dec;31(12):937-43. 
  • Lee SH, Park D, Yang G, Bae DK, Yang YH, Kim TK, Kim D, Kyung J, Yeon S, Koo KC, Lee JY, Hwang SY, Joo SS, Kim YB. Silk and silkworm pupa peptides suppress adipogenesis in preadipocytes and fat accumulation in rats fed a high-fat diet. Eur J Nutr. 2012 Dec;51(8):1011-9.
  • Pritchard EM, Valentin T, Boison D, Kaplan DL. Incorporation of proteinase inhibitors into silk-based delivery devices for enhanced control of degradation and drug release. Biomaterials. 2011 Jan;32(3):909-18. 
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