What Is Metabolism?

Metabolism can affect how much a person weighs. Photo by i yunmai on Unsplash
Metabolism can affect how much a person weighs. Photo by i yunmai on Unsplash
  • Metabolism converts food to energy, which we need to perform even the most basic of biological functions.
  • A calorie is a unit of energy. There are 3,500 calories in a pound.
  • To lose weight, one must create a calorie deficit either by eating less or exercising more.

Metabolism is the name of the biological process by which the body is able to transform food into energy. The calories that are in food and drinks are actually a measure of that energy. When your body metabolizes food, it takes those calories and mixes it with oxygen. The result is a release of energy, which allows the body to function. Therefore, metabolism is a crucial biological process.

Metabolism and Body Weight 

Metabolism has an effect on your body weight based on the amount of food you eat and the amount of physical activity you get. 

A calorie is a unit of energy. There are 3,500 calories in a pound. Therefore, if you consume an extra 3,500 calories beyond what you require to function, you will gain a pound. On the other hand, if you burn an extra 3,500 calories in addition to what you require to function, you will lose a pound. The process of burning calories in food is known as thermogenesis.

If you consume more calories than you burn, you will gain weight. If you burn more calories than you consume, you will lose weight. These are basic laws of biology that are true even for those who have a “slow” metabolism: If there is a calorie surplus, it will always result in weight gain, and if there is a deficit, it will result in weight loss. A pound is a pound no matter what. However, metabolism does play into how quickly that pound can be shed.

You might think that your body needs energy (calories) only to function during vigorous activity like walking or running, but that is not the case. Your body needs energy for all functions, including those automatic processes like breathing, blood circulation, and cell growth and repair. Although these are basic biological functions that we have no control over, they still require the energy derived from the food and beverages we eat. That is why it is important to follow a diet that is full of wholesome foods that offer our bodies the best nutrients possible.

Basal Metabolic Rate

The basal metabolic rate (BMR) is the minimum number of calories that your body needs to execute the elementary functions of living. Consider the BMR as the number of calories you would need even if you slept or relaxed all day.

There are many online calculators that will easily calculate your BMR based on data that you provide about your sex, weight, height, gender, and age. Here is the precise calculation:

For men: 

BMR = 65 + (6.2 x weight in pounds) + (12.7 x height in inches) – (6.8 x age in years)

For women: 

BMR =  655 + (4.3 x weight in pounds) + (4.3 x height in inches) – (4.7 x age in years)

There are a few main factors that help determine your BMR:

Body composition and size: Muscle burns more calories and fat, so people who have more of a muscular physical makeup will burn more calories even when they are not active. Also, larger individuals tend to torch more calories while at rest because their bodies require more energy to function. 

Sex: Men tend to burn more calories than women because they often have more muscle mass and a lower body fat percentage. Again, muscle burns calories faster than fat does.

Age: Muscle mass usually decreases as we age, while fat increases. Because fat burns fewer calories, your metabolism will slow down as you age.

Physical activity: Physical activity is the opposite of rest, so it will obviously burn more calories. It includes any type of movement, not just working out. Incidental movement like walking around your home and even fidgeting while waiting in line is what scientists call non-exercise activity thermogenesis, or NEAT. This is why so many people participate in the fitness band trend. All of those steps add up as part of your daily physical activity.

Metabolism Issues

When people have trouble losing weight, many times metabolism is blamed. However, it really has to do with your body’s needs, not the metabolic process. There are only two instances where weight gain is caused by a slow metabolism: 

Cushing syndrome: If your body produces too much cortisol, it can result in weight gain. It may also cause fatty tissue deposits on some parts of the body, including the face, midsection, and upper back between the shoulders. Cushing syndrome may also cause high blood pressure, bone loss, and even type 2 diabetes. However, it is treatable, particularly when it is diagnosed early.

Hyperthyroidism: This is the term used for an overactive thyroid gland, which means it is making too much thyroxine. When too much of this hormone is present, it can cause you to lose weight unintentionally because thyroxine increases metabolism. It can also be treated if diagnosed early.

There will always be those individuals for whom weight loss seems easy, and there will be others for whom it is a struggle. The same goes for individuals who are trying to gain weight. While calories are the same no matter what, body weight is affected by any or all of the following factors:

  • Genetics
  • Hormones
  • Diet
  • Lifestyle and environment
  • Sleep patterns
  • Stress
  • Level of physical activity

Creating a Calorie Surplus or Deficit

Experts recommend a one to 1.5-pound weekly weight loss goal that is the result of a good diet and exercise regimen. To lose one pound per week, you should create a calorie deficit of 500 calories per day, and to gain one pound per week, you should create a calorie surplus of 500 calories per day.

500 calories x seven days = 3,500 calories, or one pound lost/gained.

Keep in mind that while the BMR is good to find out how many calories you need for basic biological function, you actually burn many more calories on a daily basis. The better way of determining your daily caloric needs is with the Harris-Benedict Equation, which takes your BMR and multiplies it by your level of physical activity to get a more accurate calorie burn.

Sedentary lifestyle: For example, if you mainly sit at a desk for most of the day, multiply your BMR by 1.53 to get your daily caloric needs.

Active lifestyle: If you have a job that keeps you on your feet most of the day or you exercise regularly, multiply your BMR by 1.76 to get your daily caloric needs.

Vigorously active lifestyle: If you have a job that keeps you on your feet most of the day and you exercise regularly, multiply your BMR by 2.25 to get your daily caloric needs.

For example, if a person has a BMR of 1,300 calories, works an office job, and does not work out, this is the person’s daily caloric needs:

1,300 x 1.53 = 1,989

If that same person worked out several times a week, this would be the daily caloric needs:

1,300 x 1.76 = 2,288

The key is exercise. The more one exercises, the more one burns calories. Many people would prefer to exercise more than to eat less, which is why the Harris-Benedict equation is so helpful to a diet program. 

It All Comes Down to Science

Even though everyone’s body is different, the science still remains. When more calories are burned than taken in, weight loss will always be the result. When more calories are consumed than burned, weight gain will result. Weight loss can be difficult for many people, but it all comes down to determining the proper diet and the right amount of physical activity. 


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