Chocolate bars for weight loss. But only if there is collagen too

You know those chocolate-covered protein bars that could replace a meal but are often used with great guilt as a hunger-busting snack? Well, at the congress underway in Malaga of the European Society of Obesity Eco 2025, it was discovered that lightly sweetened dark chocolate bars, provided they are supplemented with collagen, in this case bovine, can also make you lose weight. In fact, those who ate them - reveals a Spanish study published in Nutrients - lost twice as much weight as those who didn't, moreover with better results in terms of not only satisfaction but also reduction of blood pressure and waist circumference and with an improvement in liver parameters. Not to mention the increase in muscle mass and reduction of body fat.

The role of collagen (bovine)

The credit, however, would not go to chocolate, as many of us hoped, but to collagen, a protein found in connective tissue, in this case of bovine origin, and which, treated in a certain way, is able to increase in volume in the stomach up to 20 times more than the initial volume, causing an understandable sense of satiety and therefore pushing you to eat less. Collagen is also cheap, easy to find, digestible and safe and could be used as a tool to lose a little excess weight.

It gives a sense of fullness

“Many weight-loss drugs are expensive,” explains Paola Mogna-Peláez , from the University of Navarra in Spain, “and our interest in collagen is also due to the fact that there are no known side effects associated with its intake.” As to why collagen would make you lose weight, the answer is clear: “The structure of collagen can be modified to make it absorb more water, which allows it to increase in size and give that feeling of fullness when it swells in the stomach, which reduces appetite and leads to weight loss.”

Mediterranean diet and two bars a day

Mogna-Peláez and colleagues conducted a 12-week randomized study with 64 people between the ages of 20 and 65, overweight or obese: half were women, average weight 83.9 kg, average BMI 29.65. All participants were given instructions on the diet to follow – the Mediterranean one – but half were given two commercially available chocolate protein bars with collagen (10 g of collagen per bar), to eat every day with a large glass of water before lunch and dinner. The collagen had been treated to absorb more water, so it would increase in volume.

The results

And now for the results: the participants were followed (and measured) with specific tests periodically. At the end of the 12 weeks, those who had eaten the bars had lost more weight than the control group (3 kg versus 1.5 kg), and this despite having consumed the same number of calories. In addition, systolic blood pressure had dropped by at least 8 mm Hg in the collagen group while in the other group it had increased slightly (0.4 mm Hg). Waist circumference had dropped by 2.8 cm in the bar group and by 2.5 cm in the control group, BMI had dropped by 1.2 (versus 0.78). The collagen bar group also felt less hungry, levels of leptin, a hormone that induces a sense of satiety, were lower in both groups but at the end of the study they were higher in the collagen group. Levels of ghrelin, a hormone that simulates appetite, had also dropped. None of the participants complained of side effects and in the bar group, the taste of the lightly sweetened dark chocolate that coated the bar was deemed excellent (with a score of 8.8 out of 10).

Did collagen “build” muscle?

As for non-fat tissues including muscle, they increased in the collagen group, suggesting that there may have been “building” of muscles. A sign that the weight loss had not translated into loss of muscle but of fat, explain the researchers, some of whom however have a conflict of interest since they work for the company that produces the supplement and protein bars.

“Participants felt less hungry, which could have led them to eat less and therefore lose weight,” Mogna-Peláez explained. “In addition, collagen could have helped build muscle, which we know burns more calories than fat. And it is also possible that collagen can change the composition of the microbiome in the stomach, which could help control appetite and therefore weight loss.” And new studies to investigate any effects on the composition of the microbiome are about to be launched.