"Not sure how to do fasting with exercise."

You should try it. I predict you will be very surprised.

Not only am I able to complete a power lifting regimen (1.5 hours, squats, deadlifts, basic stuff) in a 16+ hour fasted state but I sometimes find myself having more energy to do the lifts than in a non-fasted state.[1]

In two years I have never needed to stop short a resistance workout due to lack of energy (or whatever I used to worry about before I tried it).

Yes, you will need to more carefully budget those 4500 calories over the non-fasted blocks of time - you'll still need those calorie inputs. I suggest nut butters and avocados but whatever works ...

YMMV.[2]

[1] This is also true for my aerobic running workouts, but to be fair, I cannot do my full blown wrestling workout (60 mins of training followed by 4-6 5min rounds) in a fasted state.

[2] Something I found very surprising as I aged into my forties is that I used to think my exercise regimen(s) were the significant factor in my metabolism and calorie usage. In reality, if you add up how many calories you use lifting weights for 1.5 hours or running 5 miles, etc., it's quite modest ... the major contributor to my very high metabolic rate was just background metabolism. I mention this anecdotally because if you have difficulty without meals it's instructive to really consider how much of that is due to the workouts (which burn a (relatively) small amount of calories) vs. your actual background metabolism. It also suggests that if you have a negative response to IF now, it's worth trying again in five years as your background rate will naturally drop - even if you maintain the same (or higher) athletic output.

I am in my early 30s. I am wondering if you've been able to do this while making a push for higher weights? I'm currently training to move from 1300 total to a 1500 total. Regarding burning calories I agree, I've felt in myself the calories are more to repair/heal after your workouts.

What benefits are there beside increased energy? I don't have a problem with my energy levels on my current regiment, I could do more exercise to burn more off.

"I am in my early 30s. I am wondering if you've been able to do this while making a push for higher weights?"

I'll bet it's not optimal for significant strength gains.

I think it's possible, however, and it's really just a calorie math problem: if you require X calories per day to acquire whatever strength or weight gains you just need to be sure to hit that within 8 or 6 hours.

Which might be challenging, from a digestive standpoint.

I think I use about 3000 calories per day and can get that in two meals (implying a 16 hour fast) without any trouble, but when I do a 24 hour fast (implying one meal) I need to be careful and selective about that one meal ... and I probably go into a net calorie deficit over a 48 hour period as a result...

> I'm currently training to move from 1300 total to a 1500 total

I'm not sure how heavy you are but those are already advanced (elite?) level lifts assuming you mean a 1300lb B/S/DL total. Since you must have been training for a number of years now you're probably going to struggle to get stronger if you're not on a caloric surplus. I'm not an expert though.

Yeah, I'm not sure if people who recommend IF ever tried to exercise while hungry.

My lifting weights go down by at least 10-15% if I haven't eaten anything that day. Tried lifting in the morning before breakfast - didn't go too well either, just put me in a bad mood because I felt too weak.

You have to allow time for adaptation to the different kind of training... One session on an empty stomach from a fasting newb is not the same as someone who is metabolically adept at fasting training.

Lots of people are exercising while fasted. Body builders, power lifters, and athletes across the strength/endurance spectrum. For things like camping or distance jogging, being able to start at 6:00 and go until 16:00 without food is a game changer.

And, no: people who are training fasted aren't training hungry... Their hunger chemicals dissipate after 20-30 min because they're fasted ;)

I do a powerlifting routine and sometimes work out while fasted (16+ hours). Doesn't make a difference to me to be honest but I haven't tried a 24hr or multi day fast. However, my lifts are quite sensitive to sleep patterns and if I'm not well rested my lifts can suffer 5% or so (15% seems pretty large? That's a 45lb difference on a 300lb squat!).

I am not super strict with when I eat, make sure I get enough. But I agree that my lifts suffer more if I haven't given myself enough rest or time between workouts - that's a bigger detriment to lifting.

Well, I never even came close to a 300lb squat, so 10-15% isn't that much for me.

Also, I wasn't really proper fasting, just hungry because of skipping 1 meal.

Workout after IF isn't an issue for me anymore. But I definitely felt some nausea when I first started while doing some of heavier lifts like squats and deadlifts. I think it's just about giving your body time to adapt.

I can't speak to that same level of energy needs, however while fasting you generally have a constant level of energy supply from fat reserves - and in fact it can feel like you have more energy because your body isn't using energy to digest.