You didn't look 18st when I brought the, er, Fatboy round. I'm amazed. You are quite tall though Dave, you hide it well.Congrats on the weight loss.
I don't have any plans at the moment for a diet. I'm hoping that the starting to exercise will be enough.
I'm not overly concerned about my weight, I just want to lose the wobbly bits and get back into some of my old clothes.
For the record though, I'm currently:
49.5" round the belly
47" where my waist used to be
47.5 hip/butt area
I have found myself in a similar situation with breathing and heart rate, mostly due to overwork. I have lost a stone just by swapping FROM porridge, toast, cereal TO bacon, eggs and mushrooms. I've reduced my sugar and carbs, but upped the protein. No existing on one lettuce leaf, that's not sustainable. I'm not into diets and didn't go full keto but just reduced my carbs and sugar a bit, increased fruit, protein etc as well as upping my exercise as much as I can whilst working too long.
Swimming is supposed to be good too, low impact and all round, as you know if you were smashing out half a km in your lunch break! Good luck with your mission.