A few years ago, before I got cancer, my doctor told me that an ideal weight for someone of my height and build was around 185 or 190 pounds (84 to 86 kg). Since I'd been hovering around 200 pounds for some time, I didn't worry too much about it. I was relatively healthy (despite my long-time Type 1 diabetes), eating reasonably well, cycling to and from work, and so on.
Then, of course, came the diagnosis. Over the next three and a bit years, among a hell of a lot of more alarming things, my weight fluctuated wildly—as low as 145 pounds (in mid-2007) and as high as 215 pounds (a couple of years later).
When I started on my latest chemotherapy regimen in December, at first I seemed to be losing about 5 pounds each treatment, which wasn't a good trend. I adjusted what I ate (i.e. more, when I could eat), and things stabilized. Guess where?
Yup, between 185 and 190 pounds, pretty much.
I would not advise this method to reach a weight your doctor recommends for you, however.