Hi , I am a T1D and have spent the last 6 years trying to manipulate diet and exercise to achieve good BG levels . You are having high BG levels but your A1C is normal which means at some point you are experiencing lows or even hypos . Without a CGM or multiple regular fingerpricks you have no idea what your blood is doing in response to exercise , food volume or type . Initially you need a baseline without shakes , IF or any other adapted eating program . Establish a typical calorific needs diet based on your BMI and spread this throughout the day . Invest in a CGM for a short period , Freestyle Libre would be fine which will provide 14 days of 24 hour data per sensor . Keep a food diary , I use Myfitnesspal . After 2 weeks you can use your libre report and food diary to cross compare your data . At present there are too many variables to make a call . You may be pre-diabetic , you may be T2 you may have LADA ultimately developing to T1 ( my own diagnosis ) identified by positive tests for T1D anti-bodies , etc . I know how you feel with your GP it took me 18 months of pressure to finally get the anti-body tests despite having a normal A1C at the beginning and then months of extreme overeating to push up that A1C . One more thing , exercise is vital in conjunction with a balanced diet and a lot more successful as a lifestyle change than IF etc but whatever you choose it really has to be data driven tailored for you , all the best