text: You should jog at a comfortable pace (you should be able to say a sentence semi-comfortably) for more than twenty minutes. Slow down if you need to. Stop if you have any chest pain. \n\nThe first 5 minutes or so are more of a warm-up: go a little slower at first, then increase your speed. Also, cool-down after your 20 minutes are up (start with a power walk and wind down to a good "mall pace"). Don't forget to stretch before and after a workout- it will make your workout more productive. \n\nAs for the workout itself, for the first 20 minutes, you're getting cardio benefits (aerobic exercise). After 20 minutes, you're in anaerobic exercise...you're no longer burning fat, but building muscle. Muscle will increase your Basal Metabolic Rate (BMR), which will increase the caloric need of your body...so it helps you to lose even more weight!\n\nAs for treadmills v. outside: it's a matter of person preference: \nTreadmills:\n   Advantages: help you keep up your pace, can vary terrain/incline to your preference, can see the calories you're burning \n   Disadvantage: sometimes it can be more difficult to breathe indoors\nOutside: \n   Advantages: ever-changing scenery, cleaner air \n   Disadvantage:less control over terrain/incline\n\n\nEnergy requirements depend on the speed, duration, and incline of your workout, as well as your current health status.