Longer fasting periods in IF are usually for the purpose of limiting time to not get as many calories as one would usually get. The idea being more of a controlled weight loss strategy that utilized the benefits of fasting more acutely but not having the long term damage on internal organs and such that being chronically fasted can have.

Gaining muscle requires having a calorie surplus. You may gain some muscle being at a slight deficit and consuming the proper amounts of protein (which others have said is recommended at that .6-1 gram/kg body weight) and being new to weight training but the longer you do weight training and have those muscle mass increases the more difficult it is to add more muscle without that surplus.

This leads to the problem, the purpose of intermittent fasting conflicts with the protocol of adding serious muscle. One is designed to limit calories and one requires more.

Something I’ve heard that I liked goes to the effect of ‘losing weight comes down to number of calories, but the composition of the body comes down to quality of food consumed.’ I believe both quality and quantity of the food we eat is important.

IF has shown to be a good way to go about making positive changes for one health in terms of being able to be implemented and stuck with. I guess I would say just look at your goal, adjust what needs to be done for that main goal, and if IF helps you stay true to what you’re trying to do then adjust it to what you’re trying to do in terms of that goal.

I hope this helped some and wasn’t too wordy. I have my bachelors in exercise science and I’m working on getting my masters in exercise physiology. I’ve taken a lot of nutritions and sport nutritions, etc. classes and read a lot of textbooks with recent findings.