There is a fun study that took a bunch of toddlers and let them eat from a well-stocked and balanced buffet for several days. While each meal or snack would cause many of today's parents to fret over the food pyramid (one meal might only be bread, another only fruit for example) the kids uniformly ate a balanced diet when looked at over a period of days. The kids intuitively knew they needed balance, and they got it!
In terms of portions...
Toddlers do not eat predictable portions. Their intake is erratic, which can be scary for parents, particularly if a child is small or has a history of illness. It is normal for most toddlers to eat very little at some meals, and then make up for it with a very large meal or snack. Once parents recognize this as normal, the worry can ease, as well as the pressure a parent might feel to get a child to eat a certain amount, but no more.
Most children under five routinely eat what they need and no more in terms of calories. (When served a large portion, these kids ate only what they were hungry for.) Parents must learn to foster and nurture this gift, not undermine it. (Many parents might push "one more bite," or limit a hungry toddler to an arbitrary portion, or feel pressured to feed fruits and vegetables at every sitting. This pressure often backfires– with kids eating fewer fruits and veggies, or gobbling more than we think they should after being restricted.)
I watched this unfold with my daughter and its pretty amazing. I initially worried if she ate only carbs and protein one meal, but then the next snack would be a clementine, a pear and some milk, or cherry tomatoes and bread. Over a few days, the variety in the diet can be really astounding.
How to foster the child's inner voice
1) Maintain the division of responsibility in feeding. You put a variety of food on the table . Your child chooses from the foods and decides how much and whether to eat.
2) Model listening to your body. "My tummy is full, I'm going to stop eating."
(This sends a better message than, "I've put on some weight, I really want more potatoes, but I should stop now or I'll get fat.)
3) You might ask "Is your tummy still hungry for more apples?"
4) Help kids distinguish emotions from hunger. One friend told me about a time when her almost 3 year old asked for a cookie. He seemed sad, and she sat him down and asked if he felt hungry, or just sad and if he might need a hug. A long cuddle followed and he forgot about the cookie. His needs were met.
Its this notion that what and how much we eat largely should be determined by our bodies and our hunger- not by our brains. Eating becomes too much about control, "shoulds" and deprivation which fundamentally distorts our ability to listen to our bodies. We eat until we're uncomfortably full, we skip breakfast to save calories and our hormones go crazy and we're ravenously hungry by noon. Or we've gotten stuck on the diet roller-coaster where we deprive and reward with food. I will be training in November to help adults learn to tune into their bodies again. It is harder for adults to relearn than it is for kids to maintain or relearn. So for now my mission is to reach as many parents as I can to protect and nurture the child's inner voice.