Does your significant other...

[Crankin]

I am with my DH almost all of the time... we do almost everything together, including cycling. Yea, I know some think this is weird or even bad, but we don't have any issues. Even though he is faster than me, he does his fast rides on his commutes;it's been many years since he went out and rode with groups, besides the ones we lead.
That said, I do a lot more of a variety of physical things.... while DH and I also x country ski and snow shoe together, with a little hiking, he does not run or do any lifting, core work. For years, I went to the gym and he played tennis. But other than that, he was a slug.
I am one of those people who "could never be with a______." Fill in the blank. I need to be around people who have similar interests and values, not just DH.

[Becky]

You do have to manage expectations, some people will get peeved off with the amount of time cycling eats up, especially if you are training for an event. Either the other person is participating too or that they have something they like to do while the other is cycling- otherwise resentment sets in.

This is true, regardless of the activity and regardless of whether it's shared or solo. DH and I have gone through stages where one person's hobby takes up more time than the other thinks it should. Sometimes it's him, sometimes it's me, but the net effect is that feelings are hurt.

Right now, I think we're doing alright with balancing everything. Communicating about plans and expectations has been key. I can't be mad at him for not meeting my expectations if I never told him what they were.

[Susan]

Some years ago, I tried to convince DH that we would need to do some kind of sport. I couldn't get him off the couch, so some day, I started to go running on my own. (The truth is, I would have wanted someone who pushes me because it was hard to push myself. But finally I realized that I had to do this for me and could not expect someone else to do it.)

After a few month, he joined in. I think in the end it wasn't very funny to sit on the couch alone, and it isn't that easy to watch someone else being active and convince yourself that being lazy is all that great. In the end it was him who convinced me to buy a bike after a little while.

I'm really happy that he did. Being active has become a big part of our life and we spend a lot of our time cycling or running. I don't know how this would work out if he still wouldn't want to join me, because there wouldn't be much time left for doing something together and there would be a lot of happy moments that I couldn't share with him.

[Cataboo]

I tend to spend almost all my free time biking or kayaking or skiing or hiking or... Dating or being involved with someone who doesn't do those activities wouldn't make a lot of sense, basically because I'd never see them. If it's a rainy evening, I do tend to call friends who don't bike or kayak to see if they want to get together for dinner..

I'm perfectly fine doing all those activities on my own, but it's nice having someone to do it with

[Biciclista]

Reread your original question though. It seems your problem isn't how supportive/unsupportive your BF is of your individual interests, but what few interests you share together. I would agree that lots of things change during a long relationship, but the biggest predictor of the future is the present. If it bothers you that your BF isn't active, seems isolated and down, and is generally not particularly energetic, I think you need to face those facts. It just sounds like you're trying to explain away some valid feelings that you're having. And it doesn't matter how others deal with/accept/adapt to this issue. What matters is how YOU feel about it.
I'm not trying to make a mountain out of a molehill, but to me, this would be a significant issue worth sorting out in some fashion, because if you think it's draining now, just wait
until you have a house or kids or ailing parents or illness to deal with.
.

exactly what INdysteel said, and further, he discourages you from joining him in the kitchen?
If I were you, I would feel very lonely in a relationship like this one.

[emily_in_nc]

My DH is an even more avid cyclist than me; in fact, he got me my first bike early in our marriage. This year, he had ridden 18 days straight until yesterday (b/c we're traveling). He's faster/stronger than me and has done ~4K miles this year already. I've "only" done around 870 miles this year and am quite a bit slower. But we do market rides together (he carries more panniers and groceries), and easy/recovery rides for him. Or I'll join him when he's part way through with his ride and do half the miles he's doing. So, we do a nice mix of solo and "together" rides.

We also take a lot of walks together, and in the past have done kayaking, hiking, and so forth together. We also enjoy cooking both together and separately (he cooks more than me since he's retired). I think we have a good mix of solo and together activities.