It sounds as if he hasn't turned one just yet - until he does, keep him on the formula. The day he turns one, though, go ahead and make the switch to whole cow's milk. Don't wean him - just switch. Period. Toss all the formula out or give it away, whatever, but don't give it to him anymore. Some toddlers don't eat very much. Look at it this way: your stomach is only about as big as your clenched fist. That's true for babies as well (although with how much they drink, it doesn't seem accurate, I'll admit). Your son might be a light eater, and that's fine, you shouldn't ram food down his throat if he's not hungry. As long as what you DO give him is balanced and nutritious, don't worry about him not getting all the things he needs. One piece of advice is to think in weekly terms, not daily: has he gotten his fruit/veg/meat/dairy for the WEEK, not for the day? This will help you from going mad on the days when all he wants is bread or bananas or (if you're lucky) broccoli. If you're worried that he's drinking more and eating less, try easing him off the liquids. Don't give him so many liquids in between meals, and when it is mealtime, give him his food first, and the liquid later, after he's eaten some. He'll be less likely to fill up on milk or water or juice that way. (I don't know how much juice you give him, but juice tends to be very filling - if you can cut juice out for a few days, that will help.) Good luck!