Spanish Researchers Find Inexpensive Supplement Could Double Weight Loss Results
Could a common protein found in your body’s connective tissue be the next affordable weight management solution? New research suggests collagen supplements might offer significant benefits for those seeking to lose weight without expensive medications.
A 12-week clinical trial presented at the European Congress on Obesity (ECO 2025) and published in the journal Nutrients has revealed that participants consuming collagen-enriched protein bars lost twice as much weight as those who didn’t take the supplement, while experiencing numerous additional health improvements.
The findings come at a time when many are seeking cost-effective alternatives to expensive weight loss medications that have recently dominated headlines. Unlike these medications, collagen appears to work through a novel mechanism that creates a natural feeling of fullness.
How Collagen Creates a Feeling of Fullness
“Many weight loss drugs are very expensive,” explains researcher Dr. Paola Mogna-Peláez, of the University of Navarra, Pamplona, Spain. “We were interested in collagen because it is a protein that is cheap and easy to obtain and is not known to have any side-effects. It is also a compound that the public is familiar with.”
The secret to collagen’s effectiveness may lie in its unique structure. Dr. Mogna-Peláez notes, “Crucially, collagen’s structure can be modified to allow it to absorb extra water, which leads to it growing in size.”
This property allows the collagen to expand in the stomach after consumption, potentially creating a sensation of fullness that reduces overall appetite and food intake.
Impressive Results Beyond Weight Loss
The randomized controlled trial involved 64 individuals aged 20-65 years with overweight or obesity. All participants received healthy eating advice based on the Mediterranean diet, but half were also asked to consume a chocolate-flavored protein bar enriched with collagen (10g per bar) with water before lunch and dinner.
After 12 weeks, the results showed multiple significant improvements in the collagen group compared to the control group:
* Greater weight loss (3kg/6.6lb vs. 1.5kg/3.3lb)
* Decreased systolic blood pressure (8 mm Hg reduction vs. 0.4mm Hg increase)
* More significant reductions in waist circumference (2.8cm vs. 2.5cm)
* Larger decreases in BMI (1.2 units vs. 0.78 units)
* Improved liver health measurements
* Increased fat-free mass, suggesting potential muscle growth
Interestingly, these improvements occurred despite both groups consuming similar calorie amounts, suggesting collagen’s mechanism extends beyond simple calorie restriction.
How Does It Work?
The research team proposes several possible mechanisms for collagen’s weight loss effects.
“Our results indicate that, by swelling in the stomach, the collagen made the participants feel less hungry, which would have led to them eating less and so losing weight,” Dr. Mogna-Peláez explains.
The questionnaire results confirmed this theory, showing the collagen group reported feeling less hungry and more full throughout the study period. Laboratory analysis also showed higher levels of leptin, a hormone that induces feelings of satiety, in the collagen group.
In complementary animal experiments, the researchers found that collagen decreased levels of ghrelin, a hormone that stimulates appetite. Perhaps most impressively, the supplement swelled to almost 20 times its original size in stomach acid and demonstrated low digestibility – physical properties that likely contribute to its satiating effect.
Additional Benefits Beyond Weight Management
Beyond just weight loss, what makes these findings particularly promising is the potential muscle-preserving or even muscle-building effect of collagen supplementation.
“Collagen may also have led to the participants building muscle and we know that muscle burns more calories than fat,” notes Dr. Mogna-Peláez.
This could create a virtuous cycle where increased muscle mass leads to higher metabolic rates, potentially supporting long-term weight management beyond the initial intervention period.
The researchers also suggest that collagen may influence gut bacteria composition, which might further aid weight loss and appetite control – though this remains an area for future investigation.
Palatable, Practical, and Side-Effect Free
Unlike many dietary interventions that suffer from poor compliance due to taste or convenience issues, the collagen bars in this study received high marks for palatability. Participants rated the chocolate-coated bars an impressive 8.8 out of 10 for taste.
Perhaps most importantly, none of the participants reported any side effects throughout the 12-week trial period, supporting collagen’s reputation as a well-tolerated supplement.
The collagen-enriched protein bars used in the study are already commercially available. The research team is now conducting a larger trial to explore the mechanisms in greater detail, with particular focus on potential effects on gut microbiota.
For those struggling with weight management who find prescription medications financially out of reach, these findings suggest that collagen supplementation might offer an accessible, effective alternative worth considering.
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