You should talk to a doctor about this. They need to take your bloodwork and give you an actual answer. You already know that but just a friendly reminder.
That being said, my broscience-take would be you were overtraining and not eating enough, specifically from complete protein sources. Probably not getting enough quality rest on top of that. Unless you are fat/keto adapted, doing HIIT without shit for glycogen in the tank is gonna be pretty rough. Unless you live in dietary keto, over time you’re gonna be ravenous for carbs/glycogen if your body is getting HIIT every day.
I’m just some guy on the internet though, for real go talk to a doctor. even if its just the urgent care they can give you a full blood panel and submit it to insurance as preventative.
You’re eating more than a days worth of food in your eating window.
You can try lower carb to facilitate weight loss, mentally choose to eat less during IF/OMAD, or extend your fasting to add/rolling 48
Are you male or female? I had lots of weight issues despite counting kcal and fasting and the Internet was not the solution. I found out I have a disease called lipedema and an extremely damaged metabolism because of it. Also PCOS and a bunch of other things. So you may not be metabolically healthy. Might take time to get a doctor to take you seriously but they eventually do.
Look everything can be healed and cured with fruit, if you’re mentally strong enough for fasting go on an all grape mono diet. Try 5 days if you can go longer I’ve done a month. You’ll feel fantastic, your body will change. Reference I’m 6’1 225lbs weightlifter with 20+ years experience. and fast regularly, and go on fruit diets to cure water retention, muscle soreness, or head issues (stress) etc… fruits are very powerful. Lemons are extremely good healers as well, 3-5 times a day for a week, lemons only… juice them, you’re going to feel so many positive changes in your life. Melons, berries, hydrating fruits. Use herbs like dandelion root, pine pollen etc… don’t waste your time with a Dr. the medical system is only setup to profit off of us.