David says in one of his books that it is very much an individual thing - you can't generalize about people's experiences.
He also suggests that for unexpected weight gain or, presumably, slower than expected weight loss, you go low-card for a while. You'll find plenty of ways of doing that on the web, or in your local library.
Christine Cronau's book
The Fat Revolution [
http://christinecronau.com/] is worth reading. She places quite a bit of emphasis on carbohydrates in general in addition to fructose in particular. Any carb you ingest, except fructose & fibre, ends up as glucose. If your pancreas isn't doing its job properly, you could get a build-up of glucose in your blood. Any which is unneeded for energy gets converted to fat.
If you haven't already done so, I suggest you keep a food-diary for two weeks. Record EVERYTHING you eat and calculate the amount of fructose you are taking in using the tables in Sweet Poison Quit Plan. You may get a surprise, especially if you are eating much processed food, margarine, seed oils, fast food, extra fruit and so on.
Let me know how you get on.
JohnN.