I Am Type 1 Insulin Dependent At 45 Yrs Old

I am type 1 insulin dependent at 45 yrs old pancreas ceased. At that time I was a runner 5 mi/5 days week organic eating very healthy otherwise. I am 64 and only after menopause at 56 did I begin to gain weight. I was always in 140-150 range which was perfect for me. I am now 210. Have used phentermine alone on and off for a year lost 50 lbs worked well did not start gaining weight until my dr moved and changed doctors who did not like perscribing weight loss help medicine. Although I noticed at the end the phentermine did not seem to work even tho I waited a month to take 2 months supply then off 1 month. Why is this effectiveness lost? does combining topiramate and phentermine combined do better am going to dr friday need to know thanks