The ads are served by Google Adsense, not Hubpages, so they can't be changed. If it's a newly published article, sometimes you get generic dieting ads for a while. If you have enough text, then the ads should become more relevant in a few days.
Also keep in mind that sometimes Google Adsense displays ads related to the topics of other pages you visited before visiting Hubpages. If you were looking at food pages before coming here, a juice ad might "follow" you for a while.