First and foremost you need to tell him Everything you need and want to, doesn't matter if he wants to hear it or not, you NEED to tell him how you feel, stick with I statements. I feel this way when this. I feel this way when that. Keep them pointed at you, so he doesn't feel attacked and shut down before you can even get started.
Do not be afraid to tell him that he's going to end up pushing you away.
You said he's overweight too, odds are he's jealous of your progress, how you are (I'm sure) feeling MUCH better, more energy, more attention from others. He's more than likely upset that he feels he's being left behind. But all of that is on him not you.
You are not and will never be responsible for anyone other than your own reactions. If he's upset, that's for him to figure out why, is he upset that you are losing weight? If so... that's not your problem or fault or responsibility to fix for him.
My wife and I have been married for almost 22 years now.
I've known my wife was bi for 23+ years.
It wasn't until a good 5 years into our marriage that she finally "saw" it as well.
I got fat... almost 400 ish (sitting at 190ish now)
I knew that I wasn't providing her the things she needed to feel "complete" or "fulfilled" sexually.
I handled the Male side of things ok, but I got a lot of "not now, I don't feel good" etc, I constantly felt like I was being pushed away. When we started opening our relationship up, we talked.... a lot. Who wanted what, why, what were the rules, boundaries, etc. We had long, very embarrassing discussions. But in the end, we both knew where we were and what was needed to keep each of us "happy" together.
The idea wasn't to replace, it was to fill in.
I could never be a woman, even with things being hidden by fat and having breasts... I'm not woman and never will be, so, in my mind, how can I be mad at her for wanting what I can't provide. So rules in hand we started to go out and meet people, together.
I pushed her to go dance and be playful and to have fun. At first she was afraid I would be left out, and I knew I would be. And I was. But she had her time, I got some time too with a few but for the most part, it was all for her.
Then I lost the weight.
The wife was never really THAT big, she did hit 170-190 ish at one point, but that was because the whole house was eating like crap.
I lost weight and so did she.
We started working out together.
We started getting more attention from others as well.
My big issue is that, she reacts to me the way I would react when I was big. I was unhappy with myself, super self conscious, hated myself and lashed out a lot. She was reacting to the old me, not the new me. That spun some new deep convos, one we still work on.
We met our current girlfriend back in October. At first she was really into the wife, but also interested in me, but as she was more gay than bi, it was the wife she was found of, but that slowly changed, our GF had some issues with past trauma from other GFs, so I because this shelter, and the roles that my wife and I dealth with for years, reversed. Now she's the one that feels left out or pushed aside, not that she is, just that, that's how she feels. So more and more long awkward open convos and things are so much better.
I think the take away is, open up and talk. Drop your most uncomfortable information right in his lap and let him deal with it.
Most men were brought up not to express ANY emotion or weakness. I've worked hard to push past that, I know that if I"m upset, I'm allowed to be upset. I cry, I get emotional, I get sad and pissed. I get needy and want to feel loved or want to feel desired. I know that a lot of my control issues come from lack of control and other things from my past, but, the 3 of us talk often. We sit down and discuss things. We have gotten to the point where one of us can request "private time" with the other and no one gets upset about it.
It's been very VERY hard. All the body issues I face, control issues I face, jealousy, envy, etc.
All gets sorted when talk.
Not to say that you'll talk and it'll end up great for the 2 of you, but as some have pointed out above, sometimes we change and no longer fit with our spouse. And there really isn't anything wrong with that. Humans grown, change and evolve. You've made a drastic evolution. Why is he upset? Only he knows for sure.
Good luck and congrats on the loss! You look like you feel MUCH better!