From my experience and study of the matter, I would suggest you start well below where you feel comfortable and slowly and gradually work your way up. I think it is always best to take the safe and not sorry approach. You don't want to tear something or get hurt and the have to quit for a long period. Spend a couple months at a minimum with a regular schedule of work outs. You may well feel like you are not doing enough but you need to let your body get used to the work outs, motions, etc and avoid problems. Increase the weight and add a few reps every couple weeks so that by the end of the third month, you are then getting the muscles tired and start to feel the bern! I also would suggest you add some walking/jogging, jumping jacks, push ups, sit ups, and a general all around routine. Think back to those high school sports or PE classes. Maybe consider joining a team or playing some basketball or tennis or swimming or other athletic or exercising endeavors. You want to be an all arounder in my view. It may be great to look like a gym rat but that takes years (not months certainly) but you want to be healthier and not injured. Just my thoughts from an old man who doesn't practice what he is preaching but would like to if he had the time and resources available. It is good to exercise at any age and losing weight is mostly a diet issue, not exercise, in my view.