Don’t make it a diet to lose weight, just eat as healthily as possible and enjoy the riding.
I started riding a bit further to work about 5 years ago, straight away nearly 10kgs melted off in 1-2 months, no problem. I stayed at that weight, put a bit on last summer (only 1-2kgs) after breaking a wrist, decided to cut out the pack of sugary snacks at work, I’ve now lost a further 3-4kg (and it plateaued quite quickly this time too). I allow myself to stuff my face after a big ride with whatever is about, and puddings are also allowed, but no grazing on sugary foods.
At times it is quite challenging (when tired and demotivated in the shops at lunch on a work day) The main thing that keeps me going is that I feel good and I’m riding and climbing better than ever, and I feel I’m setting a good example to my kids with my weight/body shape (and hopefully will get to spend a couple of extra years with them due to this too!). I’m not walking about constantly feeling hungry, either – when I’ve tried just cutting down on how much I eat, I do feel hungry constantly and seem to get ill very easily.
On the good side for you, you’re not putting weight on, which I assume you were before. You’ll be getting fitter too. I do a lot of exercise (about 160 miles a week (30-60 of those on the mountain bike) plus a session at the climbing wall in a normal week – holidays I just do what I feel like though). I couldn’t manage anything like this if I’d not started somewhere.