Helping a hen gain weight? (Recently Broody)

[Ravynscroft]

6 years after this was written im wondering if this is still conventional knowledge because I don't see how protein will put weight on

Excessive weight loss is due to muscle mass decreasing once any fat stores are depleted... healthy weight gain is accomplished by increasing protein since muscle is made of protein...

Feeding high calorie or fatty foods doesn't give them healthy weight gain, just fat gain...