I would challenge the idea that you are “overeating” during 1.5-2:00 VO2/Threshold sessions. It’s almost impossible to consume enough food during such work to be “over eating.” Do the extra work if you think you can absorb it, but not because you need to burn calories from your intervals. Also, take it slow adding that much additional volume on top of a HV plan. Big jump from 10hrs/week to 15-18 hrs even if it’s zone 2. Good luck! Maybe add an hour a week and see how that goes.
I’m pretty sure that overeating during these sessions is a thing. I tend to put a lot of food near my bike and eat it even during cooldown “as a reward”.
Last 4 weeks, my weight jumps from 73kg to 75kg while it was stable/decreasing during previous weeks. I’m probably eating around 4500 kcal / day while my training is around 1100-1400 kcal and normal expenditure around 2500 kcal.
I’m not tracking it with absolute precision but my nutrition was on point some weeks ago ; I’ve just added extra food so pretty easy to have an intuitive insight about extra calories.
It’s just some extra calories but it added up for 4 weeks.
I wouldn’t just shove an extra 7.5hrs into a HV plan because it’s z2 and because more is better.
You need to be ready for your next planned workout.
You need to benefit from the extra volume.
You need to fuel your rides and sort out your diet, regardless
I would look at adding an extra ride on Tuesday this week, if that goes well, add another to Thursday next week. Then look at whether you need that rest day. And so on.
Monitor your sleep, mood, aches and pains and any other health markers you already monitor as you go.
I would not add 7 hours a week of training to address perceived overeating during the existing 6 days a week of training. I think you need to step back and reevaluate what you’re doing before you crater your training. You say you’ve added extra food and seen weight gain. Maybe look at that balance before increasing training. Reconsider how you are treating fuel as a reward.
Extra volume is good but I would stagger the jump up to 7-8hrs additional training over a few weeks to get used to the increase and ensure you can handle load and not put your key workouts at risk.
Ref weight, if you are planning to do additional rides then you are going to need to fuel these to some extent, especially if you need to do your key workouts later in the day otherwise you run the risk of being under fuelled for them and in turn may over eat more during/ after those workouts or fail them.
All subject to actually trying this for a week but as others have noted take a step back at review all contributing factors.
Diet off the bike, don’t pick the highest volume plan and add more hoping to negate calories.
I’d recommend speaking to a sports nutritionist with experience dealing with endurance athletes.
I find over eating on the bike during threshold and VO2 work manifests as GI distress and or stomach pain.
If you have extra time in the morning to add on Z2 volume, but don’t have time to extend your other workouts, do the extra Z2 when you can, I found even adding in a 30m brisk walk/jog every lunchtime gave me extra on the bike fitness.