My dd has always been a fairly good eater (never huge portions though) but for last week or so, eating little of her main and just wanting a yogurt or fruit (although wouldn't turn down a sweet snack).
I don't know whether to remove the sweet stuff and try and encourage the main or whether that will be making more of an issue of it and I really want to avoid food battles!
It is pretty normal, once they get a taste of sweet stuff, to want that all the time.
I believe that it is important at this stage to make it clear that the sweet stuff is only offerred once the main meal is eaten. If they know that they can refuse the main meal and still get the sweet bit then they will do it.
My dd did this at 18 months and I cut out yoghurt and fruit. It was fine and much less stressful than I thought it would be! I didn't talk to her about it or tell her she wasn't having a pudding if she didn't eat her dinner. I just got her down from the table when she had eaten her meal and moved on to doing something else.