Question: Our little boy is 2 years old, and we are still giving him a large amount of formula milk at bed time.

He is not a good eater, and we don't want him to get hungry in the night.

Is it recommended to give extra milk (he often has at least 15 fl oz), or to let him go hungry so he is forced to eat his food?

Answer: 
I saw one of my sisters-in-law go through a similar situation with both of her girls (one is five; the other is four), and it looks like I'm gearing up to go through the same thing with my daughter (18 months).

Her girls (and mine) were/are big drinkers and drank/drink A LOT of milk. They ate (and still eat) very little. One can make the argument that because they drink a lot, they aren't super hungry at dinner time which is probably a somewhat valid argument. Unfortunately, when you have a child whose weight and height consistently fall in the 5th percentile and below, you get into the habit of doing whatever you can just to get calories into their bodies. My daughter and my SIL's youngest still wake up in the middle of the night and want milk. My SIL's oldest no longer does this.

As long as there is no evidence to suggest that your child is having trouble with his oral development (he can chew different textures, he talks, and does all those things that he should do at his age), then I'd say it's probably ok. Not ideal, but ok. He's probably not going to go to college with this same strange quirk. Maybe you could try weaning him--giving him less and less milk at bedtime until he gets none. If he's still getting whole milk, you could try switching him to 2% and the reduction in fat might encourage him to eat more solids.

Regardless of what you choose to do, it's been my experience that they more or less grow out of it eventually. My niece did, my daughter is starting to outgrow it, and I'm willing to bet your son will, too.
If he is old enough to verbally communicate that he wants bobo at bedtime, then he's old enough to understand you telling him to eat his dinner.

You're not going to initiate direct change of this habit without a significant amount of stress. what you can do tho is change it indirectly.

Since the goal is better timing for getting full, you might load up at dinner on foods he likes (meal foods, not fun, snacky (read: processed) foods) and completely change brands of formula. you would then, *indirectly* entice him to change his habit. it would probably result in shifting his sleep habits and diaper changes as well. 

However...

My opinion is that I don't think you should force the issue. I'm generally not a fan of attempts to line-up a baby, in some way, with parental sensibilities. Kids this age are driven as much by what their body is telling them as they are by habit. They age (mentally) quick at this age (a baby's brain is more active at ~2-2.5 yrs than at any other time in life) and my opinion is that you should be patient. I'll bet that if you gave it some time (unless this has already been going on for weeks or a couple months) that the routine will change soon enough anyway... when their body is ready... like the next growth spurt.