I could have written your post 16 months ago, apart from the giving up smoking and steroid inhaler bit! Those two things are not going to help.
I do sympathise. It's so, so hard to break the cycle.
In March 2015 I weighted 111kg, at 172cm tall. Which is about 17st 6lb at 5' 7" I think. I was a solid size 18 - but pushing a 20 on top. I got down to 76kg at my lightest, still battling with it and am aiming for 70kg (which is about 11st 4lb). Am currently 80kg.
The ONLY thing that has worked for me was lots and lots and lots of walking. And - you're not going to like this - calorie counting.
In March last year I bought a FitBit. I realised that I was doing around 3,000 steps a day or less, when the recommended amount is 10,000 steps just to be healthy. for weight loss you need to try to achieve 15,000 a day. It meant a complete radical change to my lifestyle - making time for walks in the evening after work and at weekends (I don't have kids so easier for me, I guess).
I combined this with using My Fitness Pal to try to get to grips with what I was eating and how many calories I was taking on board. I lost over a stone in the first month - some of which was probably water weight.
You need to burn roughly 3,500 more calories than you consume to lose 1lb. So if you want to lose 16lb in 8 weeks - which is very achievable - you need to have a calorie deficit of 7,000 per week.
Work out your basal metabolic rate - the amount of calories you burn just by existing. There are loads of online tools to check.
Set yourself an exercise goal, monitor your food intake. Eat loads of salad, fruit, lean protein. Don't "diet" as such, change your diet.
I'm currently walking around 16,500 steps a day and aiming for between 1000 and 1300kcal a day. Weight is coming off at around 1kg/ 2lb a week (only been back on this for 3 weeks, holiday to Greece looming in September)
I'm typing this in a hurry as I am at work but hope some of that was useful. Good luck x