Yep, a pound of fat is 3500 stored calories, regardless of how much someone weighs (95 pounds or 395 pounds). So anyone who wants to lose a pound of fat has to take in 3500 fewer calories than they need that week (through limiting what they eat) and/or burn off 3500 stored calories of fat (through exercise). Almost everyone discovers that they need a combination of reduced calories AND increased exercise in order to lose weight.
It's all math
- calories in versus calories used in a day. Creating the calorie deficit is what forces our bodies to turn to stored calories for energy and makes us lose fat. As a sidenote, I recently saw a slide of a fat cell and it looks just like a little storage container for Crisco oil. I mean, it really is FAT that we're storing in our bodies in all our little fat cells! Slimy, oily fat. Very gross!
If someone wants to lose 1 pound of fat per week, they need to create a 3500 calorie deficit through reduced eating and exercise for the week. That works out to 500 calories per day of reducing food intake and/or increasing exercise. If someone wants to lose TWO pounds of fat per week, their calorie deficit would have to be 7000 calories for the week, which works out to 1000 calories per day.
Hope that helps!