Well, I guess it's because I eat too much and don't move enough. Quite simple, really.
Of course, there are lots of more complex reasons too. Mental health is definitely a factor in my case, but I don't want to use that as an excuse. Learned behaviour is also an issue - I learned at an early age to self-soothe with food. And my poor coordination skills (and possible dyspraxia) meant that I found PE humiliating, and didn't really learn to appreciate the benefits of exercise until quite recently. Deep down, I suspect I'm also quite lazy. And I feel overwhelmed by how much weight I have to lose, so it's easier to just keep comfort eating in order to take my mind off it.
I have wanted to lose weight for ages, but Covid-19 has certainly helped to focus my mind with regard to this issue. I feel like I've stupidly put myself at increased risk, and it has made me fearful. Of course, I know that there are many other risks that are also associated with being obese. It isn't just this virus, but it has been a good kick up the backside.
I've been exercising every day since mid March, and I'm trying to watch what I eat, but I'm not crash dieting because I want the change to be sustainable. I'm limiting portion sizes and trying to eat more fruit and veg, less junk. I've lost a few kilos so far, and my overall fitness has definitely improved, but I still have a long way to go.