Is this adequate cardio for now?

61 year old female, genetically modified to resist exercise! Wake up call when realised put on 30 lbs in the last 8 years or so. Quit smoking and hit menopause at the same time.

5' 7" and weigh 160 having lost 10 lbs in one month. Currently aiming to eat 1200 - 1400 hundred cals/day. My exercise is on the treadmill. 4mph for one hour. I do this 6 days a week. I am working on increasing the incline and am now between 2 - 3%. I fear hurting my knees and therefore doing this gradually.

I know I should start weight training and will do so. In the meantime, I read about the amazing exercise regimes that many members do each day. I am sure I will never reach such feats.

Any comments?

that's really great...you've made so much progress already. an hour on the treadmill at 4mph is really good and quite sufficient. that's considered a brisk walk, and an hour is more than enough to meet the exercise recommendations!! try not to compare yourself to others who might be partaking in "amazing exercise regimes" because there is a wide range of physical fitness and activity levels which does not speak of the progress that you are personally making. congrats and you are doing the right thing by taking precautions so as to prevent injuries to your knees!! 

This is wonderful exercise! I adore walking! And as soon as you get the incline rising your work out will be even better but do take your time! Sooner or later you'll be able to do walking intervals too which will mix it up ever more! If you are scared for your knees though using the elliptical machine may work better for you because it's less impact. 

That is fantastic. Take care to maintain your body tissue; in your diet you should have enough protein for that. If you lose about a pound per week, your diet is fine. Exercise will make your body system burn more fat (and use protein of your tissue, if your intake is low).
The calories needed daily for the body at rest is 13 kcal for each pound of body weight, excluding your body fat. Say, your body fat % is 30, leaving 70% net weight. Then, the amount of calories, required for a body in rest, is: 0.7x13xbody weight .