Regardless of salt and fat - anything with preservatives, emulsifiers, sweeteners, and most stabilisers are toxic to your gut bacteria.
Pretty much every day new research is published which connects the state of our gut bacteria/microbiome with illnesses which, on the surface, have nothing to do with your gut.
For example, it's increasingly clear that what we eat has a direct impact on our mental health - particularly anxiety and depression. It's also looking likely that eating highly processed food like instant noodles causes changes in our brain which make us crave more highly processed food, with an inevitable impact on the likelihood that we will be obese, and all the health outcomes associated with that.
As someone said upthread - almost everything we've been taught about 'bad' food is wrong. Eat anything you like that is not processed - for eg. potatoes are great. The most important thing, the thing we should all burn into our brains and have tattooed on our hands is not to eat food that's been fucked with.
It's a nightmare massive shock to the system at first - even those of us that think we cook from scratch aren't really avoiding processed food, because most stock cubes, sauces and flavourings, even 'posh' ones, have got shit in them. Likewise other stuff - 'artisan' wraps for eg still have the same shit in as the cheapest own brand ones. It's all marketing, and it's cynical as fuck.
At first it made cooking insanely time consuming - but once I'd worked out which products I could use and sort of started a system in terms of what I could bulk cook and prep ahead, it's not so bad. I still feel a bit Amish, but it's not as bad as feeling like your fucking with your children's mental and physical health every time you give them something to eat.