The Path of the Crimson Furnace has developed a cycling technique that they use in conjunction with their Iron bodies to eat as many spirit-fruits and sacred elixirs and pills as possible. They gorge
themselves on sacred beast meat and sacred herbs, and then digest as quickly as possible.
Their Iron body involves stuffing yourself to bursting and then using life madra to accelerate your body, so that you digest it quickly. After about two weeks of this, combined with some pills they have developed for the purpose, your body becomes able to do it naturally. It's a great all-purpose Iron body; they are able to receive further benefits from elixirs that improve the body, and much of what they eat strengthens them and makes them tougher. The only downside is an accelerated metabolism: now they HAVE to eat all the time.
At Jade, they have a cycling technique to go along with it. It allows them to milk further benefits out of restorative pills and elixirs, and extracts aura from the things they eat, improving advancement.