Combines "diet" and "activity" in a memorable word, and is a .com. Wouldn't be able to sell it to a "type-ins" buyer, but maybe $100-$300 to someone wanting it for a clever business or product name.
I mean a buyer looking for a name that surfers might type in directly as "name".com instead of going through the search engines. In other words if you were looking for a diet you might type in "diet.com". Dietivity.com would not likely be typed in that way, but it would be a catchy, action-name for a newspaper ad, billboard, etc. that could be remembered without writing down until the interested party had a chance to get online.