"wingmark" > ha scritto nel messaggio
>
> Normally, "junk food" like foods from fast food restaurants or chips and
> sweets are known to be bad because they make you fat. Now, I also heard
> that this type of food is also bad for a thin person trying to gain
> weight. How is that? And what's the main difference between junk food
> and healthy food?

One person's junk food is another's ethnic comfort food. There's a lot of
argument about this.
To me junk food is food which provides a lot of calories without much
nutritional value. Spongy, sweetish bread, french fries, desserts of most
kinds, compilations of fatty, underflavored things in sandwiches...
You don't want to eat much of this because it will make fat inside your
blood vessels and your organs as well as where you think you want it. If
you need to gain weight, you need to get bulkier in muscle and strong bones
as well as have some subcutaneous fat.
I'm not against the idea of earing junky stuff once in a while. It needs
not to be the mainstay of your diet. Weight that isn't fat is your friend.
Google Charles Atlas.