Ds3 is not at all picky, but he's a very light eater, we'd been worried about gain a long time before he started to loose weight beginning about 9 mos ago, when my milk went back to colostrum. This got flagged as a real problem about 6 mos ago, and became a serious concern about 4 mos ago, when a possible cause other tan light eating was ruled out.
We got a lot of weaning talk from some quarters, but if I refused him milk, he'd refuse to eat anything else at all, so I went back to my gut on that one real quick.
I can't say we've really fixed it yet, but we are seeing improvements with a few of the most recent things I've tried. None of the suggestions we recieved (except here ;)) helped, and for the most part, they made it worse. The one exception is the leftovers thing described above, which we now do in a slightly differenty form.
So, we're still in the trenches, but this is what's helping for now...
This website:
http://nutritiondata.self.com/facts/pork-products/2209/2And stuff like:
http://library.thinkquest.org/11226/main/c14txt.htmWhich can be searched for by googling "digestion of _____" pretty straitforwardly.
An absolute moritoriun on ANY discussion of digestion not including nutrition. This has been known to piss off ECEs and science center digestion interpreters. I'm happy to piss people off if my child eats. If an apple leaves anything's bum as poo, I say "but did it have the peel on, 'cause if so, the Vitamin k absorbed would be MUCH higher" Trust me, it pisses people off, but it's important, because DS doesn't want to have to pee/poo any more often than is strictly necessesary.
Occaisional praise when eating well. Not every time. Just sometimes. Especially praise about him to someone else, especially if I can catch a chance when he thinks I don't know he can hear. This was hard at first, becasue it happened soooo rarely. At first it was "Hey, [name] ate half a cheese slice by choice this morning!" once a week or so. ug.
When we are out, I bring a wide variety of snacks. He gets to pick, once he's picked, he has to finish it before he can pick again. Leftovers go back in the bag, untill he finishes them. This can take all day, and does not apply to mealtime, just snacks. But since when we started he almost never ate at mealtimes, it was pretty intense. Some days it means he only eats one rasin all day. But it keeps him from just asking for things and not eating them. If he wants to *look* at an apple, he has to finish eating the rasins. If he wants to ask what part of a pig bacon comes from, he has to eat the rasins, too. I won't discuss any food other than the snack available, and I will only discuss that snack if he's actively eating it. Once he finishes, he gets to talk about anything he wants until we get to the next snack or meal time, at which point, as long as he makes a reasonable effort to eat, he still gets to ask about anything, including food.
At mealtimes, I put tiny amounts of food on his plate. 3 macaronies, for example. If he asks for something, he gets a tiny amount. He gets about 3 choices before he has to eat something he has chosen. He does not have to eat what I put there UNLESS he is eating only one item, then he gets about 3 tiny servings, and is then to eat something of my choice, just a nibble. It seems counterintuitive, but it works. I think he gets overwhelmed by larger ammounts. This was his suggestion, multiply refined. He always gets a very small plate (usually a saucer)
We cook together a lot, becasue he loves loves loves cooking. Don't believe anyone who tells you a kid will be more likely to eat it if they cook it. They may, however, be more likely to feed it to guests, little brothers, or passing squirrils.
If he wants to eat, and we are in a place where there's a rule about not playing while eating, we try to find neutral ground, so that he can play/listen to a book/talk as he prefers while eating. I bring food up to his room, we picnic on the living room floor. The food comes out to the sandbox. Whatever. If he's affraid he might loose his train of thought he'll starve himself. The reality is that knowing I'm willing to let him do this means he usually is willing to sit and talk while eating. Most of the time if sitting is enforced he eats noting, because he's worried about whatever he's been taken away from.
It sounds a bit exhausting writing it out, but I guess I wanted to think it through again, anyway. Mainly, it's just "do the oposite of everything they tell you!"
Probably none of this will work at all for you, since most kids really don't starve themselves, the ones that do are probably just as different from each other as they are from the norm 
Man I'm longwinded lately. Sorry.
-Mich
