Anti-Obesity Effects of a Collagen with Low Digestibility and High Swelling Capacity: A Human Randomized Control Trial

Abstract

Background/objectives: Collagen is a protein formed by very long amino acid chains. When conveniently treated, it can incorporate water into the net, thus increasing its volume and mass. The present work aimed to evaluate the potential anti-obesity effects of bovine collagen that has been technologically treated to increase its water retention capacity in an acid pH medium, with the objective of inducing satiation.

Methods: Collagen's digestibility was tested with a pepsin digestion test. Its swelling capacity was tested in an acid pH medium simulating gastric conditions. Postprandial levels of ghrelin in response to collagen supplementation were tested in rats. In a randomized control trial, 64 subjects with overweight/obesity were allocated in two groups: supplemented daily with two protein bars enriched with collagen (20 g per day) for 12 weeks, or control group. Anthropometric and biochemical measurements were assessed in all the participants.

Results: This collagen showed a low digestibility (<60%) and high swelling capacity (>1900%) in vitro. In humans with overweight and obesity, this collagen significantly reduced body weight, body mass index (BMI), systolic blood pressure (SBP), and fatty liver index (FLI) and increased fat-free mass when compared with the control group. A significant reduction in the sarcopenic index; total, troncular, and visceral fat (measured by DEXA); and serum leptin levels were observed in the collagen group at the end of the intervention, with no differences with respect to controls. Collagen reduced the sensation of hunger and increased fullness and satisfaction. In male Wistar rats, collagen decreased postprandial blood ghrelin levels.

Conclusions: Collagen supplementation (20 g per day for 12 weeks) reduced body weight, BMI, waist circumference, fat mass, FLI, and SBP in humans with overweight and obesity, which might be related to the increased sensation of fullness and satisfaction reported by the volunteers after the intake.

Keywords: blood pressure; fatty liver; ghrelin; obesity; sarcopenic index; satiation.

Figure 1

Flowchart showing the volunteers who started the intervention trial, those who dropped in each visit, and those who finished the study in each group.

Figure 2

Effects of the supplementation with collagen on weight and BMI reduction in overweight/obese humans in Visit 2 (V2) and Visit 3 (V3). Weight loss (A) and BMI loss (B) of the control and collagen-supplemented groups. Data are represented as the mean ± SEM. Control group is in white; Collagen group is in grey. p = p-value when comparing both groups at each time.

Figure 3

Effects of the supplementation with collagen on body weight, BMI, systolic and diastolic blood pressure, fatty liver index (FLI), and waist circumference at baseline (V0), Visit 2 (V2), and Visit 3 (V3). Data are represented as predictive margins of the mean ± confidence intervals of the linear mixed models. Adjusting variables used in the linear mixed models are shown in brackets. ie = p value of Interaction effect between Control and Collagen groups when comparing V0 vs. V3. *, **, and *** p-value < 0.05, <0.01, and <0.001, respectively, within V0; † p-value < 0.05 within V2; and ‡ and ‡‡ p-value < 0.05 and <0.01, respectively, between Control and Collagen groups.

Figure 4

Main results obtained with the questionnaire of subjective appetite (QSA) when analyzed just before lunch (45 min after taking the collagen). Data from hunger (Q1), fullness (Q2), satisfaction (Q3), and thirst (Q4) are represented. Data are represented as predictive margins of the mean ± 95% confidence intervals of the linear mixed models. ie = p-value of Interaction effect between Control and Collagen groups when comparing V0 vs. V3. **, and *** p-value < 0.05, <0.01, and <0.001, respectively, within V0. ‡, ‡‡, and ‡‡‡ p-value < 0.05, <0.01, and <0.001, respectively, between Control and Collagen groups.

Figure 5

Serum levels of ghrelin in fasting rats and after the ingestion of the experimental food supplemented with either collagen or casein (2 h and 5 h). The values are expressed as a rate of change with respect to the initial value in fasting rats. ** p ˂ 0.01 vs. Casein (Student’s t-test).