What is Metabolic Rate?
When the subject of metabolism is brought up, many people are quick to offer their opinions regarding their own metabolic rate. Some say that theirs is slow making weight loss a tremendous challenge. Others brag that their fast metabolism allows them to eat all day long without little worry of ever gaining a pound. But are these claims accurate? Do these people really know what their metabolic rate is—or even what it is for that matter?
Metabolism: What is it?
Most people do not realize that metabolism is actually a two-part process when it comes to digestion and how food is broken down and taken into the body. The first part of the process is what is known as the catabolic reaction. The food you eat is too big to go through your intestinal tract so this process breaks it all down so that it is able to go through normal digestion easily.
The second part of the process is called the anabolic reaction. This is where those small pieces are used to form new tissue and complex molecules that eventually end up in your vital organs to give you the nutrients your body needs to sustain itself. Many people think of metabolism as digestion, but it is more of what happens in order for digestion to occur properly and what happens with regards to what your body is able to digest.
There are people whose metabolism works so quickly that no matter what they eat or how often they eat, their weight will basically stay the same. While they are usually the envy of most people, this can be dangerous from a long-term perspective. These people may gorge on unhealthy foods with no fear of weight gain, but can suffer from other health effects like high cholesterol and type 2 diabetes.
For people with a slow metabolism, weight control can be a constant battle. These people must be a lot more careful as to how much they eat and how often. If there last meal is still in the process of being metabolized, where does that leave the next meal they are scheduled to eat? Luckily, with both a fast and slow metabolism, there are several lifestyle changes that can either speed up or slow down the process. The first thing, though, is to know what your true metabolic rate is.
Do you Know Your Metabolic Rate?
This may be difficult to believe, but your body is always burning off energy by way of calories. It does not matter if you are running, sitting, biking or sleeping. The body is on-duty all day long burning off calories in order to function. Your lungs are at work, your heart is at work and everything else inside of you. The rate at which your body does this is what is known as your metabolic rate.
Two types of metabolic rates exist: resting metabolic rate (RMR) and basal metabolic rate (BMR).
RMR: Your RMR reflects the minimum number of calories your body will burn each day if you did absolutely nothing, hence, resting metabolic rate. There are ways of measuring your RMR through equations based on several factors including gender, age, height and weight. Knowing your RMR is a good starting point in knowing just how many calories your body utilizes on its own.
The equation used to get your RMR is referred to as the Mifflin equation and is as follows:
Women: (10 x weight) + (6.5 x height) – (5 x age) – 159 = RMR
Men: (10 x weight) + (6.5 x height) – (5 x age) – 4.5 = RMR
In addition to this formula, Dr. Melina Jampolis, a physician nutrition specialist in California, adds “When you test your resting metabolic rate, you must then multiply that number by an activity factor that usually ranges from 1.3 to 1.9, depending on how physically active you are every day in your job and also during exercise.”
BMR: Your BMR is a bit trickier when it comes to getting an accurate measurement. The proper way of taking a BMR measurement is to have you resting in a reclined position in a dark room after you just woke up from an eight-hour sleep along with twelve hours of fasting (this is because your digestive system needs to be completely inactive). As you see, there is a lot more involved than a simple equation to get this type of reading.
So why are these numbers so important to know? Well, it is a good gauge on how many calories you need each day to maintain your weight, gain weight or lose weight. For example, if your RMR is 1850 calories and you want to lose weight, you would want to eat less than 1850 calories per day. Remember, the body can sustain itself on those 1850 calories—eating above that amount will do nothing but help you pack on the pounds.
Of course, you also want to incorporate a healthy diet and effective exercise program into your weight loss plan. By adding exercise (both cardiovascular and strength training—preferably in a circuit-type program), you will see even greater weight loss since you will be burning off even more calories. Just be careful not to compensate for this extra burn by eating extra calories.
What is important to remember is that as you do lose weight and become more active, your RMR is going to change so it is necessary to recalculate that number in order to stay on the right road to achieving your weight loss goals. Also keep in mind that several other factors will affect your RMR like your age, your activity level, the amount of muscle you have, pregnancy, your genes and the amount of food you eat.
Knowing your metabolic rate can be a handy tool when determining how many calories you need for weight loss, weight maintenance or weight gain. What does not require any calculating is that eating a healthy diet and engaging in a workout program designed to maximize your metabolism should be a regular part of your life no matter what your reasons for knowing your rate may be.
Craig Ballantyne, CSCS, MS
Certified Turbulence Trainer