The Zen of Calories

Part Eleven: Metabolism

The Body Revisited

The human body is a carbon-based combustion engine, operating at roughly 37.0 degrees Celsius, or 98.6 degrees Fahrenheit.

It needs fuel and oxygen to operate, and the way the body changes the food you eat into energy and building blocks for internal consumption is called metabolism (from the Greek metabole “change”).

Metabolism — From Food to Energy

This conversion is achieved by a complex biochemical process, where calories — whether from carbohydrates, fats or proteins — are chemically combined with oxygen to form cellular building blocks while also releasing the energy your body needs to operate and function.

The total number of calories you consume in a day is called your total energy intake. The total number of calories your body burns each day is called — you guessed it — your total energy expenditure.

The following three factors constitute your total energy expenditure:

Basic needs

Amazingly, the majority of calories consumed in any one day are used by the body for basic maintenance, for even when at rest your body requires energy as fuel for organs, breathing, blood circulation, adjusting hormone levels, as well as for cell production and repair.

The number of calories used to meet these basic needs are referred to as your basal metabolic rate (BMR, we discussed that above) — basal refers to base, fundamental, what forms or belongs to the foundation (of your body).

A person’s BMR typically constitutes as much as two-thirds to three-quarters of all calories consumed. It is also noteworthy that basal energy needs stay fairly constant and do not easily change.

Food processing

The process by which the body digests, absorbs, transports and stores the food you consume also requires energy. This activity uses about ten percent of the calories you consume. As with basal energy needs, the energy needed to process food remains fairly constant and is not easily changed.

Physical activity

Physical activity, however, is a factor you can control: by playing tennis, by walking to the store, by hiking, cleaning, cooking; in other words, by moving.

Physical activity accounts for the remainder of calories consumed, roughly fifteen to twenty-five percent.

The frequency, duration, and intensity of your movements (activity) determine how many calories you burn.

Metabolism and your weight

While it may seem logical that low metabolism should result in obesity, this is rarely the case. It is, in fact, quite uncommon for low metabolism to cause excess weight.

First Law of Thermodynamics (1LTD)

Instead, it’s our old friend 1LTD (which you may want to tattoo somewhere easily viewed as a constant reminder) that again rears its conspicuous head, for weight gain is most often caused by an imbalance between total energy intake, and total energy expenditure. In other words: by consuming more calories than your body burns.

To lose weight — and yes, the broken record analogy springs to mind — you simply need to create an energy deficit by consuming fewer calories than you burn — by eating less while increasing your physical activity.

Your Calorie Needs

If everyone had identical bodies, we could easily determine basal energy needs. But — and I would add, luckily — this is not the case. Therefore, to establish your calorie needs you need to take into account your body size and composition, your age, and your sex.

Body Size and Composition

In a nutshell, larger body mass requires more energy (that’s to say more calories) than smaller body mass. Also, as you may know, muscle burns more calories than does fat; so the higher your muscle to fat ratio, the higher your basal metabolic rate (BMR).

Age

Age brings with it a decrease of muscle in favor of fat, which lowers the basal metabolism, and metabolism itself tends to grow more inefficient with age. This means that your calorie needs naturally decrease as you grow older. Keep that in mind.

Sex

As a rule, men have more muscle and less body fat than women of the same age and weight. This is why men generally have a higher basal metabolic rate and burn more calories — just sitting still (or using the remote) — than women do.

Burning Calories

When it comes to burning calories, there isn’t very much you can do about your metabolism or digestive system — speeding them up or slowing them down. Your only option, realistically speaking, is to increase daily exercise and activity to both burn calories directly through movement and build muscle tissue which in turn burns more calories.

And the key to exercise is regularity. As in daily. Take a 30-minute walk every day. It’s an excellent aerobic way to burn calories. As you age, you may also want to add weight training to help counteract muscle loss.

That said, any movement burns calories. This means walking to the store rather than driving, taking the stairs rather than the elevator, playing with the dog rather than watching television, hiking, swimming, dancing. You name it. Burns calories.

Bottom Line

While it is true that the majority of your energy needs are determined by your metabolism, you ultimately determine your weight by what you eat and how much of that intake you burn through physical activity.

Again: Your good friend 1LTD front and center.

© Wolfstuff