Excess protein dehydrates me and lightens my wallet more than replacing that excess protein with a bit more fat (if I am hungry).

Back when I was following Protein Power and getting my (81g/day) adequate protein, Mike Eades blogged about a Scandinavian study where women ate 100g/day. I tried it and I did, but what I was losing was water weight. I was always thirsty and even my eyeballs felt parched despite drinking an extra liter or two of water each day.

For me, adequate protein is enough to keep my nails and hair strong. During my decades of RDA and vegetarian eating (46g/day protein) I had very flexible nails that easily chipped or split into layers. They got strong when I conscientiously increased to 80g. A few months back I tried lowering protein following Rosedale's recommendation to 50g, which was primarily animal protein, not vegetable as in my vegetarian days. But my nails got weaker quickly. So I upped it and my nails and hair are strong again on 60g/day. Since I IF, I aim for at least 45g on fasting days and eat more on non-fasting days, so that over a week, my protein averages out to 60-70g/day and I feel good and rarely parched.