The size of the child's stomach and the hunger

 

It is not possible to speak of a single stomach size neither by age nor by size of the individual. The size will depend on several factors. When we are born our stomach is very small. In reality it is tiny: barely the contents of a tablespoon. For this reason, the baby needs many feedings of breast milk or artificial milk since he is not able to process all the energy he needs in a single intake. As the child grows, the size of the stomach grows and therefore the feeds can be spaced out.

The stomach is a bag-shaped organ that continually renews and adapts. Remember that hydrochloric acid is generated within it to help coagulate proteins. Hydrochloric acid is extremely corrosive, so we can assume that the internal walls of the stomach are under great chemical pressure. Were it not for the renewal of the cells that form the wall, the stomach would consume itself. 

The feeling of satiety appears when this "bag" fills up. If we get used to eating abundantly, the stomach will get bigger and the feeling of satiety will appear later and later. Therefore we will eat more.

Children, and even more so babies, act instinctively when it comes to food. If I may use the simile, they act exactly like animals: they eat when they are hungry and instinctively know which foods are most suitable for them. We, as adults, act in front of food in an instinctive way but also in a cultural way. We can eat foods that we do not like to please the person who has prepared it for us, or out of commitment or because we think about the consequences it will have on our health or because we simply want a binge.

So we have a child whose stomach will be proportionally much smaller than that of an adult, but how much? If an adult weighs 80 kg and your 5-year-old son weighs 19 kg, it is practically certain that his stomach will be at least 4 times smaller than that of the adult. We could say that the adult has a capacity of 2 liters, so that the child's is half a liter. But we probably don't know. But we can guess. 

Now we are going to study the adult. He is 171 cm tall and weighs 80 Kg. Suppose his ideal weight is 72 Kg. That is, he is 8 Kg overweight. From this it follows, in a very general way, that his rations are probably greater than necessary. So if we divide the adult's ration by four and still subtract a little, we will have the optimal child's ration. Does it seems too small ration? In the eyes of this adult, of course. But there is still more.

When we diet we must take great care of the contribution of micronutrients (vitamins and minerals) as well as macronutrients (proteins). If we eat a lot, our portions contain enough nutrients to cover the needs of our body, but when we diet we begin to suffer from deficiencies that often have to be covered with the intake of vitamin and mineral supplements. Or eating better. Much more better indeed.  The same thing happens in children. They eat less because their stomach is smaller, but their feeding must be much more efficient. Foods that do not provide enough minerals and vitamins are harmful for them as well as those that do not provide the necessary calories. For example, we make a carrot puree and give it to the child. There are certain chances that he will reject it. Parents often think that it is a problem of taste, but it happens that a ration suitable for the child's stomach made up only of vegetables does not provide enough calories: it satisfies him but does not nourish him. So he gobbles down the plate of vegetables, his stomach fills up and he is unable to eat the second plate of chicken, for example, which would nourish him 100%. For sure would have been better to mix a bit of chicken with the carrot mash. 

And there is still more. The adult often thinks that the child needs a lot of calories to grow and develop. It is relatively true. In fact, children develop a great deal of activity but they have a small body and the spectacular growth that the child had up to two years of age slow down  after that age. Growth is a consequence of age, it has a genetic component (tall parents, tall children, you know...) and there are rarely cases of poor growth in the first world due to feeding failures.

With this we already have a physiological perspective to place the possible loss of appetite in a "logical" place. Sometimes what you think is a loss of appetite is just because you think the hunger of your kid should be same as yours and that, simply from the point of view of the stomach size of the children, it's impossible.