In beginning of the game, the McDonalds logo only appears on a garbage can and if you run into it - you die. It's a positive message for health conscious parents.
McDonalds turned out to be the easiest to get a healthy meal from at the time. They had things like salads, apple slices, and a much wider variety of items than other fast food restaurants meaning that if you were to eat there every day it was much easier to make different healthy meals than it was at the others but like an order of magnitude.
Basically just skip the soft drink and only occasionally order the fries and you'll be fine.
>McDonalds turned out to be the easiest to get a healthy meal from at the time.
The McDouble is "The greatest food in human history" <https://nypost.com/2013/07/28/the-greatest-food-in-human-his...)