Nutrition : necessary energy

energievoedingOur body needs energy to stay on temperature, to maintain life processes (breathing, heart rate) move (muscle contractions), to grow and recover tissue (dead cells, wounds). That energy we get from food. The amount of energy consumed by a body in complete rest per day ("basal metabolic rate" or BMR: Body Metabolism Rate) is about 70 kcal / h, or one kcal / h per kilogram of body weight. The heavier the effort, the higher the calorie consumption (depending on condition, sex, etc.). Calorie consumption therefore depends on the activity, approximate:

    Laying: 68 kcal / h;
    Relaxed seating: 71 kcal / h;
    Unwind stand: 75 kcal / h;
    In standing posture: 78 kcal / h;
    Walking at 3.6 mph: 210 kcal / h;
    Walking to 6 km per hour: 350 kcal / h;
    Cycling to 15 km / h: 380 kcal / h;
    Swimming: 640 kcal / h;
    Jogging: 750 kcal / h.

To burn one beer (about 500 ml, 245 calories) a woman has to do 25 minutes of cardio training or 34 minutes of strength training. And a man an average 21 minutes cardio or 28 minutes strength training.

A small (or half) pizza margherita of 682 calories costs a woman an average of 71 minutes of cardio or 94 minutes strength training. A man on average 59 minutes of cardio or 79 minutes strength training.


Every year, approximately 1,000 kilos of food and drink pass through your body. Digesting some food products requires more energy than they provide. So you lose calories by eating fiber-rich fruits and vegetables such as: apple, endive, beet, broccoli, carrot, celery, cauliflower, cucumber, garlic, green beans, lettuce, onion, peach, radish, spinach, tomato, turnip, watermelon.

Food takes the route from entrance to exit in the average man in 55 hours. In a woman in 72 hours. Why, or what consequences this difference has, is not (yet) known. The food is moved in the small intestine by contractions (peristalsis) at a speed of 2.5 cm / minute.

Our body uses energy to function. If you eat more than necessary, excess energy will be saved in the form of triglycerides that consist of various fatty acids. These are stored in the adipocytes or fat cells. Proteins and carbohydrates also end up in these storage rooms.

If we consume less energy than necessary, our body starts to consume those fat cells, or better: its contents. The fat molecules are broken down into glycerol and fatty acids, which serve as an energy source. Oxygen breaks the chemical compounds. That provides energy, water and CO2. We breathe out most of the weight loss as CO2 and water.

The total number of fat cells is retained, but they are empty. They can refill by extra food, which threatens a yo-yo effect. Growing more muscle tissue helps. This causes an adaptation of the body metabolism. In terms of metabolism and energy consumption, muscles are much more active than fatty tissue. They are more likely to burn energy than to store it.

Energy can be measured in joules or calories.
A calorie (cal) is the (obsolete measure of) energy needed to heat 1 gram of water from 14.5 degrees Celsius to 15.5 degrees Celsius. A calorie is equivalent to 4,184 joules.
A joule (J) is the energy required to move a weight of 1 kilogram (kg) over a distance of 1 meter (m) with a force of one Newton (N). Electrical energy is usually measured in kilowatt-hours (kWh). 1 kWh is 3 600 000 J or 3.6  MJ (MJ megajoules). A joule is a watt second. A lamp with an electrical power of 1 watt consumes in 1 second 1 joule of electric energy.

Normally built, no heavy work performing women need about 2,000 kcal per day and ditto men about 2,600 kcal.

Our brains make up only 2% of our body weight, but consume up to 500 of the 2000 daily needed calories (25%). (In a monkey less than 10%, our brains have more volume and more connections.) The actions of other organs (heart, lungs, liver, kidneys), included organs consume 60% of the daily calories. Digestion (incl. cewing, swallowing ...) consumes 10%.

A healthy and varied diet (according to the Dutch Disk of Five (or the Flemish Nutrition Triangle) is correlated to a larger brain volume. The cause or effect factor has not yet been demonstrated.

A grown man of 70 kilograms has 161,000 kilocalories as carbohydrates, fats and proteins stored in his body tissues. In order not to lose weight he needs about 2,500 calories per day on average activity. Theoretically he has enough stock for two months without food (but drinking).
After a month, organs begin to fall one by one. First, the intestines, liver, and kidneys. Thereafter, heart and nervous system (with cardiac arrest due to lack of energy to pump).
Doctors notice at anorexia patients that the heart fails when the body mass index (BMI) falls to 12.5. From concentration camps (WW II), we know that people with few calories per day can live for months or even years.

'Dietitian: line judge.’(Hugo Olaerts)
‘The only way to stay healthy is to eat what you do not want, drink what you do not like and do what you disgust.’(Joey Adams)

The energy from food is provided by carbohydrates, fats, proteins and alcohol:

  • 1 gram of fat provides 37 kJ (= 9.3 kcal, so 9300 calories)
    § 1 gram of alcohol is 29 kJ (= 7.1 kcal)
    § 1 gram carbohydrate (sugar or starch) yields 17 kJ (= 4.1 kcal)
    § 1 gram of protein provides 17 kJ (= 4.1 kcal)

The idea that chewing and digesting some fruits and vegetables would cost more energy than yielded made appear some "negative calories" food lists between 2011-2016. Research in 2019 showed that the number of calories stated in food tables is a gross amount where the energy cost of processing still has to be deducted, but that the balance remains positive in all cases, even when chewing a raw celery stalk. So it was unfortunately a fable.

Healthy and varied diet contains all necessary substances, minerals and vitamins. The disk of 5 (Netherlands) or nutritional triangle (Belgium) provide an overview of this: move much, drink at least 1.5 liters of water, plenty cereals and potatoes, many fruits and vegetables, also some fish, meat, egg, dairy and / or replace products, low spread- and cooking fats, and a small remnant of unnecessary sweets, alcohol.

Hourly in a human body one billion old or dead cells are replaced. These are the most diverse cells, from hairs to the skin and muscles to nails. This makes our body (hair, muscles ...) annually around completely renewed.

The world would be a lot better off, if mosquitoes would suck fat instead of blood.