One good way to show proof that your intent is profit is how much time and effort you put into the venture - and not just eating. Maintain a log of your daily time spent working on your website/blog. Include research, posting on forums for answers, etc. ANYTHING that relates to getting your site launched and running. You may also want to consider adding other affiliate marketing services to the site for an attempt at additional revenue.
Also, any professional or educational background you have in the topics you wish to write about will serve you well as far as proving you have the ability to make a profitable business out of your venture. So if you don't have experience in anything you've considered adding to your site, think about some items that you are an expert in and add those as well.
The deduction is limited to 50% and it should be for your meal only - not anyone elses.
BTW - I'm a degreed accountant, fiction author and freelance writer.
Good luck!