It takes about 3500 calories to lose a pound. You can lose weight by eating 3500 calories less than your body needs or by exercising away 3500 calories.
For example, if your body needs 2000 calories a day to maintain its weight with your current activity level, if you ate 1500 calories a day for a week, you'd have a 500 calorie a day deficit. Times that times 7 and that's 3500 calories which should translate to about a pound loss in weight.
Or if you eat 2000 calories a day and jogged for 9 hours a week, the jogging would burn about 3500 calories and you'd lose about a pound.
Eating fewer calories a day is the easier way to weight loss, but exercise can supplement it and tone your body. Also, as you replace fat with muscle, you'll burn more calories.
Age 61, Height 5'9"
March 2010 145 lbs, Jan 2013 173 lbs
1st Goal 145 lbs 5/25
New goal 140