Weight loss solutions are a dime a dozen. Some swear by dieting, others by intense exercise. But for those who struggle with feelings of satiety, a new solution may be on the horizon.

In a new study out of Spain, scientists developed a collagen-based protein bar that swells up to 19 times its size once it hits stomach acid. The result? People who consumed it lost twice as much weight as those who didn’t, all without following a calorie-restricted diet.

Participants consumed collagen-enriched protein bars (10 grams of the special collagen, twice daily) before lunch and dinner. After 12 weeks, they lost an average of 6.6 pounds compared to just 3.3 pounds in the control group. But the benefits went beyond a number on the scale.

Those who took the supplement also saw drops in waist size, blood pressure and a marker for fatty liver disease. Muscle mass stayed intact. They also reported feeling less ravenous and more satisfied before meals — not because of willpower, but because they simply weren’t as hungry.

So how does it work? Researchers took standard cow collagen and altered its structure to act more like a sponge than a typical protein. In the acidic, watery environment of the stomach, it expands dramatically and resists digestion, which is crucial in helping you feel full, longer.

In short: This new collagen and protein bar is engineered to slow digestion and physically fill space, leading to natural appetite reduction. Like most newfangled dietary supplements, it might be a minute before this not-so-average snack is available in your local supplement aisle. Ultimately, it could take the guesswork out of dieting … and add a pleasantly full stomach instead.