Let's be clear here because there's a lot of jibber jabber on fasting, dieting, lifting, etc
1. Being in a calorie deficit for too long, isn't sustainable or designed for our bodies long periods of time.
2. IF/Fasting can be one tool of calorie restriction
3.IF specifically 16/8 has no adverse effects on the ability to gain lean muscle mass.
4.Exercise is a tool to build muscle, your number one ability to effectively lose weight is a calorie deficit. Exercise can aid that process but if you eat like an ass, you'll look like an ass
5. For some people, exercising in a fasted state can hurt your performance
6. Exercising fasted doesn't provide extra benefits
Please consult your doctor or dietician for your specific health and bodies needs. But put generically, let's stop over complicating this. And let's get off the high horse. If you want to fast, fast. If you want to eat all day, do it. If you want to gain muscle, you have to eat in a caloric surplus, eat .7-1g protein/lb bodyweight and lift for hypertrophy (1-3 exercises per muscle group, 2-4 HARD sets to near failure, in the rep range of 8-20, per session totalling 10-20 sets per muscle group per week). *although hypertrophy can occur from as little as 5 to as high as 30 reps.*
If you want to lose fat, you have to eat in a caloric deficit, aim to lose 1-2lbs per week, implementing strength training to sustain/gain muscle while losing weight safely to assure its mainly fat and not muscle.
This shyt is not a one trick pony or one size fits all. There's many paths to health and fitness. Choose the one that YOU enjoy and YOU can stick with. For example, you need to do cardio, but you hate running? Speedwalk, bike, skateboard. You hate lifting with a barbell? Use dumbbells and kettlebells.
But please the non-negotiables for men should be to eat at least 500g of fruits and veggies (broccoli, kale, blueberries, blackberries) per day, if you're a man eat atleast 38g of fiber (oatmeal, blueberries, chia seeds, beans) per day. Minimize sodium intake as much as possible. Drink enough water that your urine is clear or light yellow. Eat .7-1g protein per pound of bodyweight