Do it now. I am 53 and can barely walk, I am in good health, high blood pressure is my only issue besides the weight. I am 5'2 and weight 280, 320 is my highest so I have managed to drop some & keep it off for about 5 years. I don't lose, no matter what I do and I can't run or walk, so water aerobics is my exercise. You are doing the right thing and I envy you that you have the opportunity.