Also, being a software developer, you are familiar with Terms of Service. Here is FitDay's regarding your "hostage data"
You represent and warrant that: (i) you own the content posted by you on or through the Site or otherwise have the right to grant the license set forth below, and (ii) the Posting of your content does not violate the privacy rights, publicity rights, copyrights, contract rights or any other rights of any person.
By displaying or posting content on the Site, you hereby grant us a nonexclusive global license to publish the content submitted by you to the Site. You also grant us global nonexclusive adaptation and resale rights over any content and material submitted to the Site. These nonexclusive publishing license and resale/adaptation rights extend to any materials submitted "for publication" within the Site, including both message board postings and content submitted for uploading and subsequent publishing within non-message board portions of the Site. Neither we nor our staff will be responsible for any misleading, false or otherwise injurious information and advice communicated on the Site or for any results obtained from the use of such information or advice. We will not be liable for any loss or damage suffered by a user through the user's reliance on information and advice gained on the Site.
Did you read the TOS when you signed up? Your data is located on the "non-message board portion of the site", so you are out of luck.
Think of food as fuel for the body instead of feeding emotions