I like the way you approach the market. The weight loss market is a huge and highly competitive field and targetting the "dabblers" might be a good angle for you to take. As to whether to sell it or give it away, why not go with Steve's read, fire, aim approach?
Give yourself a $100 budget, buy some Google Ads, and see if you can make any money selling the eBook. If you can, tweak it, otherwise, try another approach. Giving the eBook away in order to put together an email list could also be very valuable, especially in this market, where you could recommend other people's products that have worked for you.