My family carries the genetic propensity for high cholesterol and weight retention. All three of us girls would diet, but not be able to sustain long time.
The second sister is shorter than I am, but we pretty much share a weight. :-(
Over a year ago now, she went on a diet that required NO EXERCISE to be successful. Instead, it uses strict dietary constraints to change your body's "set point" -- what it automatically seeks to reach weight-wise. Nearly all starches and all sugar are removed, Avoiding salt is also recommended. A 750 calorie/day is used for sedentary people. If you get a lot of exercise normally, the protein is increased a bit until you're okay.
She's always hopping on some fad, so I didn't pay much attention. Now, she's dropped 50 pounds, which are staying off. The second sister got on it, and in four months, went down 35 pounds (and two dress sizes)...
I went to the doctor, reported their results, gave him the web site URL, and asked what he thought. "It's hard to argue with those kinds of results."
So, I'm heading for it.