in terms of weight loss the factor that's most important is the number of calories you consume vs the number of calories you burn. at the end of the day if you've burned 2 000 and consumed 1 500 then you are in 500-calorie deficit. if you do this for 7 days then you are in 3 500 calorie deficit and that is one pound (figure that 3 500 calories = one pound). if you burn 500 calories with your exercise another 300 through the rest of your activities of daily living and then 1 200 for metabolic processes to keep your heart beating organs working digesting food and other essential functions to stay alive you have burned 2 000 calories in one day. if you consumed 1 500 calories that day you are in 500-calorie deficit. as for exercise for the same period of time and activity you will burn more at a higher intensity. if you walk on the treadmill at 4 mph for 30 minutes you will burn more than if you walk for 30 minutes at 3 mph. i suggest working as hard as is comfortable without risking injury. this will get you as aerobically fit as possible and being as fit as you can has advantages for weight loss because you probably will be able to do more activity (exercise and activities of daily living) and that will contribute to how many calories you burn all day. but keep in mind that no matter how many calories you burn with exercise you still will not lose weight if you consume more calories than you burn. if you burn 2 000 calories all day with exercise and all other activities but you consume 2 500 you won't lose weight. and keep resistance exercise like weightlifting in mind since it helps you build muscle and muscle helps set your metabolic rate so you want as much muscle as possible.
how does the amount of time spent exercising affect weight loss?