Manipulating Your Metabolism
Metabolic rates The number of calories each of us gets to consume to meet our nutritional needs and maintain a healthy body weight is a very personal calculation. Your height, sex, state of health, and activity level are the primary factors that determine your caloric requirement. Metabolic rate is also an important facet of energy balance. You can think of it as the engine that regulates all of the calories you use, and you may want to pay more attention to it as you move through your second decade.
What Controls Metabolism?
- Basal metabolic rate (BMR) - The energy your body needs to maintain basic bodily functions when you are at complete rest, such as body temperature, heart beat and breathing. It accounts for about 60-70% of your energy requirements.
- Thermic Effect of Food (TEF ) – The energy used to digest, absorb and process the food you eat. It accounts for about 5-10% of energy needs.
- Non-Exercise Activity Thermogenesis (NEAT) – The energy used for unconscious activity, like fidgeting, muscle contraction and maintaining posture. It accounts for 5-10% of energy needs.
- Physical Activity – The energy needed for deliberate movement and activity. It accounts for about 25-40% of energy needs.
- Changes in activity, body composition and diet can all affect this powerful engine, but the greatest threat of all is the passage of time. Your metabolism naturally slows down as you age.
Muscle Fuels Metabolism
Even if you maintain a stable weight throughout your twenties by balancing the calories you consume with enough regular exercise to expend them, by the time you reach your thirties that routine will no longer keep your weight in check. After the age of thirty we begin to lose about one third pound of muscle each year, or a full pound of muscle every three years. That alone can lower your metabolic rate enough to cause a noticeable weight gain by your twenty-year high school reunion.
Put another way, the average woman who eats 2500 calories a day in her twenties needs only 2400 in her thirties to maintain the same weight and only 2100 in her fifties. If she wants to be the same size at seventy that she was at twenty, she’ll need only about 1500 calories a day to achieve it.
Many people believe increasing their physical activity is the only way they can manipulate their metabolism. But there are other tactics that can help offset a sluggish metabolism now and the subtle decline that occurs with aging. Even the eats-all-she-wants girl will show signs of middle-aged spread if she doesn’t make some adjustments to stay ahead of this natural decline in the rate we burn calories.
