My husband has always been into heavy lifting and long training sessions. When I started IF he told me how it’s not possible to do the work outs he does fasted. After seeing me do it for several months and all the weight come off and my exercise almost always in a fasted state, he kinda started doing it then fully committed when he saw the weight start to come off. He’s down 50 lbs and all muscle now. He used to lecture me about why it wouldn’t work, he’s done this for 2 decades blah blah blah and then realized everything he’s believed is wrong once he started 🤣 he’s stricter with it than I am now.
I have a peloton and do most of my rides fasted. I’ve spent 2 hours on the bike at 24 hours fasted and had more energy at the end. You’ll have to allow your body to adjust but you absolutely can do it. It’s counterintuitive but only because we’ve all been misinformed about the science behind it. We know more now about how the body works than we did a few decades ago. I’d recommend trying it for a few weeks. Ease in. Start with 14 hours. Then 16. Then 18.
From all the research I’ve done in fasted state you should be able to go Zone 2 basically forever (obviously you’d need some body fat which everyone has). If you do a harder workout that would not be the case. Saturday ride in Zone 2 should be fine fasted. If you want to do a hard group ride then I’d eat first. Only 7 days into IF myself but a lifetime of nutrition and fitness research, tons of training and highly competitive cycling.
Personally an easy zone 2 aerobic morning workout and lift session is no problem fasted. Can also do a short sprint interval session fasted but it’s short. If I were trying to get faster for racing and doing serious intervals I’d do them fed.
What it comes down to is your body runs great with fat as its primary energy source. When you are fasting and have depleted glycogen, your body runs on fat.
As you are eating 3 meals a day and 3 snacks, I suspect your body is accustomed to running on glucose. It will probably take your body a little time to adapt to using fat.
It will probably be easier to maintain your training regimen if you transition gradually. I would start by eating your last meal of the day earlier so your night time fast is longer and eliminating the snacks. You don’t need to change the amount of food you eat, but try to leave larger gaps between meals.
Over time, you can narrow your eating window. You are eating quite a bit of food, so I would aim for two meals a day about 4 hours apart as your end point.