Minimal Amounts of Fish Peptide Hydrolysate Double Fat Loss Compared to Whey Isolate on Energy Restricted Diet

I certainly recommend eating fish. Whether I will be recommending fish hydrolysate supplements in the future, however, will have to be determined when additional studies with different baseline diets will have been published.
You may remember that I've written about fish protein hydrolysates / peptides before. Unlike today's article, however, previous articles dealt with the effects of fish protein in rodents. Intrigued by in vitro and animal studies showing that fish-derived peptides demonstrated antihypertensive (Hatanaka. 2009; Kim. 2012; Li. 2012; Ngo. 2011), antioxidant (Nazeer. 2012; Najafian. 2012), immunomodulating effects (Duarte. 2006), reparative properties in the intestine (Fitzgerald. 2005; Marchbank. 2008), and effects in reducing plasma cholesterol and triglycerides levels (Möller. 2008), a group of Italian researchers decided to investigated the effect of Slimpro(R), a supplement containing commercially available fish protein hydrolysate from blue whiting (Micromesistius poutassou), on body composition and on stimulating cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) secretion in 120, overweight, non-obese (25 kg/m² < BMI < 30 kg/m²), male (25%) and female (75%) subjects aged 18 - 55 year.
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Unlike the product that was used may suggest, the study was not sponsored by the supplement company. The authors received neither funding nor other external support and they also declare that they don't have a conflict of interest that may be related to patents or direct involvements in the industry. I guess it's important to point that out, even though fact that the scientists chose whey, i.e. an actually relevant control, instead of carbohydrates or just plain water, may have given away the lack of sponsorship, anyways.

Two weeks before the study started, subjects were asked to fill in an alimentary diary reporting their food preferences. A mild hypocaloric ( 300 kcal/day) diet was elaborated for each subject by a dietitian based on subject’s food preferences and habits as reported in the alimentary diary.
Figure 1: The low protein content of the diet is - as highlighted in the annotations to this graphical illustration of the macronutrient composition of the test diets - problematic, to say the least.
Approximately, 55% of energy intake was from carbohydrates, 25% from lipids, and the remaining 20% from proteins. Part of these 20% of protein were either 1.4g and 2.8g of fish protein or 1.4g of whey protein isolate as a control (I just assume that the dosage was 1.4g, because there was only one whey group), which were consumed in form of a flavored shake according to the following protocol:
"Both the active (one dose treatment arm) and the placebo products were taken as follows: ‘dilute the content of one sachet in a large glass of cool water (200 ml). Shake or stir with a spoon. Consume within 10 30 min before the main meal’. In the case of two-dose treatment arm, one sachet of the active product was taken 30 min before lunch and one sachet 30 min before dinner" (Nobile. 2016).
To be able to tell what could be responsible for advantages or disadvantages of the two treatments, the scientists assessed more than just body weight, fat mass (DXA scans), and safety of use as well as the secondary efficacy endpoints, extracellular water, and the circumference of waist, hips, and thighs. They also checked the CCK and GLP-1 levels in their subjects' blood. This is relevant, because this is how the fish hydrolysate is advertised on the manufacturers website:
"Taken daily before meals, Slimpro® increases the production of CCK and GLP-1 in the body, thus amplifying messages associated with a decrease of food intake. Promising results were reported from in vivo et in vitro trials of these molecules that may control food intake. Scientists have described this ingredient as a direct action on the hunger process" (Nobile. 2015).
As it is usually the case in studies like this, some patients were "lost". In this case, we're talking about a total count of eleven subjects who did not reappear for the follow-up check (One subject in the one-dose treatment arm, four subjects in the twodose treatment arm, and six subjects in the placebo treatment arm discontinued intervention because they were no longer interested to participate in the study). The results of the other subjects are plotted in Figure 2:
Figure 2: Changes in body composition after 45 and 90 days of dieting w/ the specific supplements (Nobile. 2016).
As you can see, double-dosing had astonishingly little effect on the subjects' ability to lose body fat. That's in contrast to switching from fish protein hydrolysate to whey protein isolate, which produced measurably, but not statistically reduced rates of fat loss and waist reductions.
Figure 3: Blood biomarker levels. (a) CCK blood levels and (b) GLP-1 blood levels. Intragroup (vs. D0) statistical analysis is reported upon the bars of the histogram. The lines report the intergroup (vs. placebo) statistical analysis. Statistical analysis is reported as follows: *p < 0.05, **p < 0.01, and ***p < 0.001. Data are mean +/- SE (Nobile. 2016).
And guess what: Even though the bars don't look like it, the asterisks over the bars tell you that these differences may be caused by the same differential expression of the satiety hormones CCK and GLP-1 in the fish hydrolysate vs. whey protein group that has been observed with other control protein in previous studies and is boldly advertised on the producer's website.
Great! Let's eat more fish... It stands out of question that the former is actually a very good idea (assuming you make the right fish choices). I have to warn you, though: Firstly, the fish protein consumed in the study at hand came from fish, but just like whey protein and milk, fish and fish protein hydrolysates will also have different effects.

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What is probably way more important, however, is the relative protein deficiency of the subjects. With only 20% of the diet being protein, the study participants hovered around at the meager level of the RDA. Since the effects of 1.4g of fish protein hydrolysate you throw on top of a low protein diet are probably very different from those of the same amount of fish protein consumed alongside 2g/kg of dietary and supplemental protein, I wouldn't guarantee and in fact even doubt that you would see a similar almost 100% increase in fat loss while dieting - and still,  the CCK and GLP-1 boosting effects of fish protein hydrolysates are intriguing | Comment on Facebook!
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