Intermittent Fasting

Intermittent fasting is a bit of an umbrella term.

A few years ago 5:2 was pretty popular and I would argue it's potentially one of the best forms of IF for weight reduction, but it's quite challenging unless you've got a fairly disciplined personality. For 2 days of the week you're significantly reducing your calorie intake, maybe to 600-800 calories, which can be challenging.

Based on the OP's reference to 16 hours fasting, I take it you're thinking of doing 16:8, with 16 hours of fasting and 8 hours of feeding window. For what it's worth, this is what I do, and it's a very do-able form of intermittent fasting, since what it amounts to is holding off from eating your breakfast. I take nothing until 12pm or 1pm and then it's an eight hour window until I fast again. The toughest part of it is if you're actually trying to lose weight, and are in a calorie deficit. But a calorie deficit sucks with any diet, to be quite honest!

In crude terms there are two potential strands of benefit associated with 16:8 intermittent fasting.

1. To an extent you may enjoy the somewhat unsubstantiated health benefits of multiple 16 hour fasts. There are ample books and articles out there. I personally suspect a lot more research needs to be done and for real autophagy to occur, if it does, I wonder if a longer fasting period isn't almost certainly required. What I would say is that my digestive system feels great on 16:8. Rarely if ever any sense of bloating or having overeaten, and prior to breaking the fast generally a sense of great clarity and 'feeling good'.

2. There is an argument that having that 8 hour feeding window lends itself somewhat to weight loss for various reasons, but to be honest at the end of the day it still depends on your calorie intake. You could eat every hour of the day in a calorie deficit and lose weight too. There's no point in eating 16:8 and then in your 8 hour feeding window you're eating 3000 calories a day... You've still got to get a sense of what your BMR is, and identify a calorie goal (Say BMR - 20%) and then figure out what that looks like in terms of food intake. But yes, I think for some temperaments IF suits this goal.

For mass gain 16:8 is still do-able, you can have your calorie surplus in that 8 hour feeding phase, but you probably want to consider making sure a greater portion of your macros are from carbs on training days, and try to train around the time you're breaking your fast, or else in the evening during the feeding phase.

Worth remembering:-

As you're not getting water via food intake during your fast period watch your water intake.

Alcohol counts towards your calories.

Black coffee and water help with any hunger pangs.