Prickly Pear Cactus Fiber, also known as Opuntia ficus-indica fiber or "NeOpuntia," is promoted as a weight loss aid primarily due to its purported fat-binding properties. Some scientific studies have investigated its efficacy. The main proposed mechanism is that the fiber from the cactus is able to bind dietary fat in the digestive tract, thereby reducing fat absorption and promoting its excretion. A few small randomized controlled trials have suggested that supplementation with Prickly Pear Cactus Fiber can increase fecal fat excretion in humans. For example, a study published in Current Therapeutic Research (2011) found increased fecal fat excretion with NeOpuntia supplementation compared to placebo, although the actual amount of fat excreted was modest.

Clinical studies on weight loss outcomes are limited and generally of short duration. One small 12-week trial showed a statistically significant but clinically modest reduction in body weight among overweight participants using the supplement. However, results are not consistent across all studies, and the overall effect size is relatively small. There is also limited data on long-term safety and efficacy.

In summary, while there is some scientific evidence that Prickly Pear Cactus Fiber may aid in weight loss by modestly increasing fat excretion, the overall quality and quantity of evidence is limited. The benefit, if any, appears small, and more rigorous studies are needed to confirm its effectiveness.