Ways to affect your BMR:

• Exercise: Depending on the length and intensity of your exercise, you can boost your BMR for several hours afterward.
• Diet: Severe dieting can reduce your BMR as your body attempts to conserve calories. This is a survival tactic and not a good idea for a healthy lifestyle.
• Increased muscle mass: Muscle burns more calories, even at rest, than fat. The greater your ratio of lean to fat, the more calories you will burn.
• Caloric needs:About 30 percent of your calories fuel any physical activity you do, from scratching your nose to running a marathon. Of course, the marathon will take significantly more than an additional 30 percent. To figure out how many calories you need for your level of activity, multiply the calories needed for BMR by the percentage that matches your activity level. If you're sedentary (mainly sitting all day), multiply by 20 percent; 30 percent if you engage in light activity (such as walking to and from the bus stop, cooking dinner, etc.)daily; 40 percent, moderate activity (very little sitting, heavy housework and gardening); and 50 percent for very active (construction work, and active and prolonged physical sports)
• Calories needed for digestion:
  About 10 percent of your caloric intake goes for fueling digestion and absorbing nutrients. To determine your caloric needs for this, add the calories for BMR and the calories for physical activity, and then multiply the total by 10 percent.