It's still really early for people to be discovering Lemmy and Kbin communities. It should get better!
LoseIt: Lose the Fat
https://www.reddit.com/r/loseit/
A community for weight-loss, primarily by means of inducing a caloric deficit.
Yeah. On Mastodon it took like 3-4 rounds of Twitter insanity to bring it into a state where you could use it if you weren't just discussing Open Source software.
For Lemmy we are currently in wave 2 of Reddit insanity, but this is the first time that Lemmy is in a usable state and has available instances. So I kind of hope we have a small, moderately active community running and in the next round of Reddit insanity people who look into lemmy can actually find this community.
I'm sure it'll happen! I've been browsing all for about a week and yesterday is the first time I saw this one. My experience will probably be similar for others (perhaps!)