People who eat very little but seem healthy?

[BlackMolasses]

Usually the people I met who ate very little had obvious signs of hypothyroidism and poor health.
But there is also a category of people who eat excessively little but seem very healthy.
I have a friend in her 20s who needs to eat 1000 to 1500 calories a day, mostly from very low nutrient sources like pasta or white rice, she is very skinny but she has a good amount of energy (+ big pupils), is very creative, has no sleeping problems, no mood problems, perfect skin etc.

How does she do it? She may have stress hormones and a very low loss of energy but it's still very little macro and micro-nutrients, is she at risk of collapsing in a few years?

 

[LeeLemonoil]

Usually the people I met who ate very little had obvious signs of hypothyroidism and poor health.
But there is also a category of people who eat excessively little but seem very healthy.
I have a friend in her 20s who needs to eat 1000 to 1500 calories a day, mostly from very low nutrient sources like pasta or white rice, she is very skinny but she has a good amount of energy (+ big pupils), is very creative, has no sleeping problems, no mood problems, perfect skin etc.

How does she do it? She may have stress hormones and a very low loss of energy but it's still very little macro and micro-nutrients, is she at risk of collapsing in a few years?

That’s the Beauty of Evolution.
While Homo sapiens has a common system with a corridor of requirements that must be met to maintain healthy homeostasis - this corridor has extremes and variables so that individuals of Homo Sapiens are fit to survive a multitude of environments.

Your example might have „good genes“ meaning that she has a good capacity to synthesize needed substances to uphold her system in a good state from very little input. Add to that her cellular abs biochemical setup is very well adjusted, efficient.

But every ultra-complex system has its weaknesses.

 

[TheSir]

One's state of health is inversely proportional to the amount of nutrition they require. Whether or not your friend's way of eating is sustainable is difficult to predict without getting to examine her mineral balance. That being said, rice and pasta will definitely deplete her body over time in absence of other nutrition.