I can recount my own experience, from some 20+ years ago, I have no scientific evidence, just the experience:
I never reached 25 stone, but, at 13 stone ( a good 2 stone over my "acceptable weight), when, at age 49, I suffered a heart attack.
On discharge from hospital, I was given advice from a Nurse, my GP, and, a dietician.
The dieticians advice was to reduce sugar intake wherever possible, and, she pointed out some "hidden" sources, in food which I thought of as "healthy". So, for example, avoid "fruit" yoghurts, instead, by plain yoghurt, and, add (frozen) fruit.
The technique I adopted to. was to read the labels when shopping, I then avoided anything with more than 10% fat, or, with high sugar levels (can't remember what constituted high, too long ago). In practice, this did not mean an unacceptable diet, although, I did have to do without Chocolate!, and, I did treat myself to some alcohol (I switched from beer to red wine).
The Nurse, and GP's advice was to be more active, but, to incorporate it into my life style, rather than "impose" it.
At the time, I was still a wage slave, so, time limited, I worked some physical activity into my daily commute (eg walk to/from metro station), and, into my daily routine (eg lunch time walk from the office).
I joined a cycling group, using a mountain bike. They rode on a picture of roads and trails. I went with them twice per week, typically doing 15 miles per outing. I found I really enjoyed this, not just the cycling, but, the commitment of meeting up with the group. The latter helped to motivate me to "get out there" on this cold, and/or wet days, when sofa and TV beckon.
Within six months, I had shed 2 stone.
Since that time, over the following 20+ years, I have kept up the walking and cycling, I am retired now, so, have more time.
I have to admit, my diet has "slipped", I do not follow a diet, although, I do tend to. eat reasonably healthily, alcohol consumption has increased, and, I do indulge in chocolate occasionally.
The net result has been a slight weight gain, but, I have "levelled off" at 11st 8oz, blood pressure is within acceptable limits, and,, at 73, I feel reasonably fit, certainly unto. cycling 50+ miles per week, with some walking inbetween.
I now ride a hybrid (Giant Escape Disc), and, tend to ride mostly on quiet roads.
Good luck.