The Centers for Disease Control and Prevention recommends five 30 minute aerobic sessions per week along with two strength training sessions. I have found combining aerobic exercise with strength training and stretching works best. The key is finding activities you enjoy so you will do them consistently.
You want to have a positive experience so I recommend starting with low-impact activities such as walking, swimming, yoga or Pilates, and brief strength training and toning exercises. You can always increase the intensity (i.e. power walking/jogging), duration (double or triple the time), and frequency (repetitions).
When you exercise moderately, your heart beasts a little faster and you breathe a little harder. Your muscles use more sugar in your blood stream, which can lower your blood sugar levels. It also makes the insulin in your body work better. You’ll get these benefits for hours afterwards.
Developing muscle tone is also important (no-one wants to look flabby, right?) You can tone with brief exercises that shape and strengthen your muscles. To jumpstart your muscle-toning, I recommend Lani Muelrath’s Fit Quickies which are great for busy people because each of the 10 video/audio exercises are 7 minutes or less.