In my younger days, I was an avid runner, although I do not have the body type for it. I continued to run regularly until I severely injured my knee a few months before my 20th birthday.

After surgery, recovery, more surgery, more recovery, etc (a total of 4 or 5 surgeries/arthroscopes) I came to the realization that to continue running would mean, essentially being crippled.

Not a pleasant prospect.
So, here I am, 47, with a knee that is usually sore, sometimes excruciatingly so, but facing the old "middle-age spread", when my doc orders me to lose 20-40 lbs. Now, I'm 6 feet tall, and when weighed, fully clothed, in his office in March, I tipped the scales at 246 lbs. I've always been big boned, but even I felt that this was a bit high.
So I made a point of cutting out as many simple sugars from my diet as I could, and really watching what I ate. I also extended my nightly walk with the dog, much to his pleasure, and kept snacking to a minimum. The result was that, seven weeks later, when I went back for a follow-up visit, my weight was down 7 lbs.

My Doc was happy, and said to keep it up. I had to drill new holes in my belt to keep my pants up, and I've actually had compliments from my co-workers about my apparent slimming down.
I can't say that it has been difficult. It took a long time to get to this point, and it will take a while to drop off another 10-15 lbs. Again, I don't expect to get below 200lbs; I haven't since I was 16, but I can be a bit fitter, and, who knows, I may even go out and buy more pants,
before the ones I now have are worn out!