Calories, the energy that drives us

We feed on micro and macronutrients, all of which are necessary for our subsistence. Through food we obtain energy, which provides the three basic macronutrients: carbohydrates, fats and proteins.

Alcohol also provides energy but unlike the first three nutrients mentioned, it lacks nutritional value.

Thermodynamics defines “calorie” as the amount of energy needed to raise the temperature of 1 gm. of water by 1º C”.

To measure the energy value intake of food we use as a unit kilocalorie (Kcal) instead of calorie, because our bodies consume a lot of energy.

The caloric intake of the chemical components we feed on is as follows:

• Carbohydrates 4 Kcals per gm.
• Protein 4 Kcals per gm.
• Fats 9 Kcals per gm.
• Alcohol 7 Kcals per gam.

How much energy do we need?

The energy expenditure of each person depends on their basal metabolism, their activity factor, the thermogenic effect and the so-called injury factor. Let us see what they consist of:

Basal metabolism. This is about the energy consumption necessary to maintain our vital functions (breathing, pumping and filtering the blood, synthesizing hormones, blinking) and body temperature.

This expenditure is affected by body size, lean mass, age, gender, race, hormonal functioning, nutritional status and the climatic environment.

Factor of activity. This is the energy expenditure linked to our physical exercise habits, that measures the energy used in the activities we perform. It represents about 30% of the total energy needs of an average person.

“Fats contribute over twice as many calories as carbohydrates and protein.”

Thermogenic effect. This includes the expenditure used in digesting food. Normally we eat foods that contain various nutrients, but from the theoretical point of view it is worth noting that digestion of proteins requires much more energy than that of fat; digestion of carbohydrates is the least energy consuming.

Dividing up the meals throughout the day causes a greater thermogenic effect.”

Injury. The latter variable refers to the energy used by the body to treat illnesses, conditions and diseases.

Do you know how you use your energy?

You use approximately 1 Kcal to read 650 words”.

Climbing stairs involves significant energy expenditure, averaging 225 Kcals per 15 minutes. Roller-skating is a less extensive activity, but still involves an expenditure of between 200 and 500 Kcals per hour.

Housework also demands abundant energy. Cleaning windows consumes about 160 Kcals every half hour, while ironing accounts for about 115 Kcals of expenditure for the same length of time.

Digestion of proteins requires much more energy than that of fats and carbohydrates”.

Much of our nutrition depends on agriculture. However, those who work in farming should be well fed, as the average farmer uses about 350 calories per hour. Therefore an 8-hour day will make him use about 2,800 calories only at the activity factor level!

Energy is the foundation of life.”

Not even when resting do we stop burning up calories. While we sleep, we have a consumption of basal metabolism that, added to other processes, causes us to lose about 300 grams of weight by the time we wake up in the morning.

As we have seen, our body requires many nutrients to supply us with the energy we need. Thus, on average, each person consumes about 21,219 kg of food throughout his lifetime. That is the weight of about 6 elephants!

References

• Perspectivas en nutrición. C. Byrd-Bredbenner, D. Beshgetoor, G, Moe, J. Berning; 8ª Edición; 2010; McGrawHill.
• Manual de Nutrición y Dietética. Ángeles Carbajal Azcona. Departamento de Nutrición. Facultad de Farmacia. Universidad Complutense de Madrid. 2013
• Cosas y Casos. Jaime Libros, S.A. 1983
• Onmeda International
• Zonadiet.com.
• Wikipedia.