My normal weight dad was dx'd with diabetes last year. He has always eaten well.

What you are saying about testing this approach makes little sense, because in the past there was much less refined sugar in the diet, and yet bipolar existed. Have you read "touched with fire"? I am about to begin. It describes bipolar in well known authors of the past - van gogh, Emily Dickinson, etc. I got this book (written by the most prominent researcher of bipolar and a fellow sufferer) because I want to know about the connection with creativity, but as a side benefit if you read it, you will realize that people who consumed far less refined sugar were still sick. Jamison is a great writer... very grabbing, engaging. Why don't you read this short book before you decide to start a year long experiment?

Also, bipolar exists throughout the world, including countries with much lower consumption of refined sugars.

Finally, the causal connection between diabetes and overweight is disputed. It could be that insulin problems first cause overweight and only years later manifest themselves in abnormally high blood glucose. At any rate, if you have a family history of diabetes, you need to try taking Metformin (if you do not develop side effects, just take it for the rest of your life), exercise and, importantly, strength train. Cardio is not enough. I am starting strength training soon for that very reason. Research shows that women who strength train are protected from diabetes. Another important measure for you is taking vitamin D3. I take 10000 IU's, living in Northern California. You might need more depending on your latitude.

Basically, I am concerned that this year long experiment might give you a tunnel vision, and you will disregard so many other things being overly focused on one thing. If you don't think that you are at risk for that, it is safe to proceed (cranberries have a lot of antioxidants to substitute for chocolate, coffee, and tea). I have noticed that the risk of tunnel vision is high I bipolar people - we do themed shopping sprees, develop obsessions, or clean until it is spotless - all are examples of overfocusing one one thing at the expense of others. Hence I am mentioning this risk to you, so that you don't become overfocused on cutting out refined sugars to the point of losing track of other important components of your health.