This reminds of cellulose in mouse studies. In a study from a few years back, called something like 'A ketogenic diet causes a unique metabolic state in mice' had to be restarted somewhere around the six month mark because the animals were dying suspiciously early. It turned out the animals weren't doing well with the cellulose fiber used in the diet, so they switched them to wheat middlings for the fiber source. Another study looked at 25 different macronutrient ratios and longevity--it also looked at calorie density. Across all macro ratios, the lowest calorie density resulted in the shortest lifespan--the seven shortest lifespans, all in a row, had the lowest calorie density. Calorie density was manipulated by adding what was thought to be harmless--cellulose fiber.

I don't for one moment think that adding cellulose in equal amounts as celery or kale would have been as damaging. I think natural cellulose, as long as you don't try to eat a tree or something, is probably usually pretty harmless. Once you dessicate it, grind it up into fine particles, cook it into chow, apparently something changes.

I did a search for 'feces' in the silicon particle study. Nothing about the calories contained in the feces. If food efficiency is being reduced, where is stuff going, instead of being used to make a bigger mouse? Unclear to what degree digestion of fat versus protein versus carb is being interfered with.

Their hypothesis is that the particles interfere with enzyme activity, no speculation about which enzymes. I'm sure the hope is that it's ones for dealing with fat.