Do read Dr Jason Fung's "The Obesity Code" and perhaps also his "the Complete Guide to Fasting". Fasting is something that your body learns and becomes capable of through practice. The nausea should diminish over time. Just work on extending your fast 1-2 hours at a time. Fasting becomes much easier after you have adopted a LCHF eating style, so perhaps that is the first step (a small low carb breakfast like coffee and an egg).
I am prediabetic and I have used the Jason Fung strategy (LCHF combined with Intermittent Fasting) for the past 14 months, and it has done me a world of good. I also bike to work (20-25 mins with some uphill that makes me puff) on nothing but a cup of coffee (either black or with a little cream). However I would have struggled to do this 14 months ago. I have brought my dawn blood glucose down from in the 7s to in the 5s. My body is getting better at burning fat instead of glucose, this has given me better biking stamina/endurance.
So basically my suggestion is to use the LCHF + IF strategy, read Jason Fung because he gives you an excellent mental model of insulin resistance and what it is you are trying to achieve (which is really motivating), and don't expect instantaneous results. Slow and steady wins the race. To keep motivated, track your progress each month. In a year's time you should see a real difference.
You are on the right track. Practice makes perfect. Push your body just a little bit at a time.
