My understanding is that the ads are automatically generated by a third-party provider and 3FC doesn't have the opportunity to select which ads are displayed or to even approve the ads in advance, so sometimes ads that seem a little off for a diet forum do show up.
I think 3FC can ask the ad provider to remove ads from the rotation, so if you find an ad offensive, like this one, you could use the "Contact Us" link at the bottom of the page to ask that 3FC ask the ad provider to remove it.
I also highly recommend the
ad-free subscription to the forum. I purchased the 6 month subscription and it is worth every penny of the $15 (that's a mere $2.50 per month) that I paid for it. No more banner ads or pop-ups!