They sort of tried this in the '90s — not in the form of suppressing the required enzymes for nutrient absorption, but rather in the form of diet foods that contained inherently non-absorbable nutrients. The downsides were basically the same — the non-absorbed nutrients had to come out. People didn't generally respond well to these products. See e.g. https://web.archive.org/web/20060113084223/http://www.zug.co...