What Is Metabolism?

Metabolism is a combination of biochemical processes that your body uses to convert food into energy. These metabolic processes include breathing, eating and digesting food, the delivery of nutrients to your cells through the blood, the use of energy by your muscles, nerves, and cells, and finally the elimination of waste products from your body. 

When people talk about metabolism, they usually aren't talking about a long list of physical and chemical processes—which is the actual definition of metabolism. We often use the word "metabolism" to describe the rate at which our bodies burn calories. This is the rate at which your body converts food into energy (calories) and then uses the energy to perform essential and non-essential daily functions. The rate at which we burn calories or burn energy is called metabolic rate. 

Your metabolic rate might change from day to day depending on your activity level, but your basal metabolic rate stays fairly steady. Your basal metabolic rate is the number of calories needed to fuel your body's essential functions, like breathing and circulating blood. Basal metabolic rate is the most significant component of your total metabolic rate. 

To determine your metabolic rate, you first need to calculate your basal metabolic rate (BMR). There are several different ways to determine BMR. The most accurate way to measure BMR is to have it tested in a lab. Some health clubs also do metabolic testing for a fee. You can also calculate your BMR using an online calculator. 

If you like to do math, you can also calculate your BMR using the Harris-Benedict Equation:

Men:  BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age in years)

Women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age in years)

Now that you have your BMR, you can find out your total metabolic rate. Your total metabolism or metabolic rate is a combination of your BMR and other variable metabolic processes like eating, exercise, and other daily movements. 

Using a fitness tracker is the easiest way to add up the number for these other processes. For example, you might burn 700 calories from daily exercise and non-exercise movement. If your basal metabolic rate is 1200 calories, then your total energy consumption (metabolic rate) would be about 1900 calories.

You can also use an online calculator to get your total number.

Everyone's metabolic rate is different. You might wonder why other people seem to have a fast metabolism and you have a slow metabolism. There may be several reasons why. There are many different factors that affect metabolism

• Age. Metabolism slows as we age.
• Gender. Men generally have a higher metabolism than women.
• Body size. Bigger bodies burn more calories.
• Body temperature. Metabolism increases when the body is exposed to extreme temperatures.
• Caffeine or stimulant intake. Your metabolism may increase if you consume a stimulant like caffeine.
• Hormones. If thyroid hormones are not produced properly by your body, your metabolism may increase or decrease depending on the hormone level.
• Pregnancy. Women who are pregnant have a faster metabolism.
• Food intake. If you don't eat enough food, your metabolism slows.
• Body composition. Lean muscle mass burns more calories than fat even when your body is at rest.
• Activity level. When you move more during the day, either through exercise or routine daily movements (like walking or standing) your body burns more calories.

There are some things that you can change about your metabolism and some things that you can't. For example, you can't change your age or your gender. But there are some things that you can change to boost your metabolism and lose weight. These include:

• Exercise. You burn more calories when you exercise. Even an easy workout increases your metabolism. Harder workouts, however, burn more calories.
• Daily movement. No time to exercise? Then move more during the day. Increasing daily movement is the best way to boost your metabolism. Simple daily tasks like walking, climbing stairs, gardening, and housework require your body to work harder and burn more calories.
• Build muscle. You can improve your body composition to burn more calories. Do strength training exercises to build muscle and burn more calories even when your body is resting. 
• Eat the right number of calories. Eating too many calories can cause weight gain. But eating too few calories can cause your metabolism to slow down. Make sure you're eating enough calories to maintain a healthy metabolism.

Your metabolism will change slightly from day to day. But if you can learn how to manage and maintain a healthy metabolism on a regular basis, weight loss and weight maintenance will be easier.