It's tasteless? AND it makes me fat? Where can I buy this wonder beverage?!?
Apparently the stuff was Quinine to fight off malaria, where the active ingredients were in a syrup in non-soluble form so it was more palatable. what it had to do with making people fatter, no idea. Maybe at the time malaria fewer burned off people's fat storages.
being fat implied that you had enough wealth to have more than enough to eat. so yes, fat = health and wealth. the whole "having enough money to starve yourself thin" is a relatively new idea.

and no, fashion magazines and mail order catalogs have ALWAYS drawn people thinner than the actual public are, this is evidenced by doing actual measurements of clothing that are still in fashion/clothing museums. :)
My mother had to take this as a girl, and according to her it was anything but tasteless. 60 years later, she still shudders at the memory.