The invention concerns a formulation having the property of fixing fats (so as to eliminate from digestion part of the fats ingested during a meal), based on cladodes of cactaceae of the edible type and at least partly non-available. The invention is characterised in that the cactaceae is in the form of powder particles whereof at least 70 wt. % have a size less than 100 νm (sieve-controlled particle size distribution). Advantageously, the inventive particles of cactaceae cladodes are in the form of granules coated with an acid-resistant film soluble in the intestine and/or with prolonged release. The invention also concerns a method for obtaining such a formulation.