I'd never heard of this Helen Gaunt before, but since this is the first post of hers I came across she has not endeared herself to me to say the least.
I can't comment on her eating habits and whether her physique is so called natural or not because I have no idea about her day to day habits. I would question whether one can naturally be smaller than Eilish McColgan though. When you are running the kind of mileage she seems to who can truly say what her physique would be at a more moderate level of activity. Sadly, Sarah does follow her and like her posts, providing even more justification to starve herself and overtrain. Weight can be a component of an ED, but ultimately it's more about mindset, compulsion and anxiety. It's also entirely possible to undereat unintentionally/without it being a psychological disorder.
Regardless of why she looks this way, this woman really needs to pick her words more carefully. Skinny is not a good term to use. To me it means weak, undernourished and ill. That is not a natural state of being, and should never be used as almost synonymous with athleticism. For somone who works as a PT, she should be ashamed, not of her appearance, but her lack of care and thought for the level of influence she has as a fast and naturally gifted runner.
I also feel a bit bitter at posts like that, as if we're supposed to break out the violins for someone who is lean and runs at a speed most of us can only dream of, no matter how hard we work. She won the genetic lottery, yet she's acting as if
skinny people face the same level of shame as those who are overweight, for example. I'm sorry but 'skinny shaming' is just not a thing, because the power balance is such that being thin is still ultimately viewed as positive by the vast majority of society. It's punching up, not down.
I'm not sure if a healthy pregnancy or two is a good way to measure health per se though? There are women in wartorn countries who give birth to reasonably healthy children despite being in a state of semi-starvation themselves, aren't there? I can't pretend to know for sure, admittedly. I'm pretty much clueless when it comes to that. So sorry, so childfree