Dietary fat intake and hormonal downregulation question : AdvancedFitness


Context and Question (decently long read)

I was / am helping a person diet to goal of “as lean as possible without getting quite stage lean” He is 6ft 180 now, started at 220.

Things had been going smoothly and normally, and we were nearing the end of the cut, or at least where I felt we should stop because we were getting low on food, guy looked awesome, and with no competitive goal it was unnecessary to get leaner and open the door to any more consequences of pushing further.

He expressed his desire to hold at that bodyweight for about a month and half so he could look peak for a few life events, and then we would feed up.

In anticipation of this holding pattern, and the end of the shredded state, and unbeknownst to me, he decided to drop his fat considerably for a final push. He basically took himself from 50g daily down to trace in one swoop. based on his food logs he is probably getting 5-8 grams a day max.

He finally confessed to me he had done this and had been eating this extremely low amount of fat for the entire 2 ish month period. I was shocked to say the least, but also surprisingly, he basically lost no additional weight, and if he did tighten up at all, it was nowhere near what would be commensurate with an extra 450 cal deficit he created by dropping the fats.

I have never had someone take their fats this low before so I am not sure both what to do.

So my question(s) are. Could there have been / be some metabolic downregulation, possibly thyroid? form basically eating no fats. If he incurred that much of an additional deficit beyond what we were holding at, why did his body composition not change at all?

Second question, how to approach this from intake standpoint now? I mean we need to get him eating fat again ASAP, but can you just feed fat back up to get things functioning normally again or is his body going to freak out and go apeshit storage mode? I mean Id like to get him up to like 30g immediately?