The way most of those ads work is through a third party such as Google or an ad broker.
The software picks up keywords in the site and feeds ads that match those words.
The level of scammery is extremely high in the supplement and diet industry as well as the "miracle foods" multi-level marketing scams.
If this were an automotive or hang-gliding site, the ad mix would be different.
"To give anything less than your best is to sacrifice the Gift."