"How many calories do I need?" — the question most often heard in the kitchen when the table has buckwheat, cutlets, and a tomato salad. What helps make sense of it isn't a calculator on your phone but understanding two things: how much energy the body spends at rest and what makes up the daily requirement. Below is a calm foundation, without promises or a race for numbers.
What calories are and the body's energy requirement
Calories measure the energy in food and drinks. The body needs this energy to function properly: to breathe, move, maintain temperature, and think. The balance is simple: if the number of calories the body expends matches what comes in with food and drink, weight stays roughly the same. If more comes in, the body stores the excess as fat and weight increases; if less comes in, the body draws energy from its own fat stores and weight decreases.
On packaging, calories are listed in kcal (kilocalories) or kJ (kilojoules), and you should look for them under the word "energy." A reference point for adults: about 2500 kcal per day for the average man and about 2000 kcal for the average woman. This is precisely a reference point, not a personal norm.
Basal metabolism: what it is and what it consists of
Basal metabolism (also called basal metabolic rate) is the minimum amount of energy needed for normal vital activity under standard conditions. The conditions are described strictly: wakefulness, morning, fasting after 12–16 hours of fasting, lying position, psychological and emotional rest, comfortable temperature of 18–20 °C.
The intensity of basal metabolism in men averages about 1 kcal per kilogram per hour, meaning a man weighing 70 kg spends about 1700 kcal per day on basal metabolism. In women this value is on average 10% lower. This energy goes toward maintaining a constant body temperature, cellular metabolism, blood circulation, respiration, excretion, the work of vital nerve centers of the brain, and the constant secretion of endocrine glands.
How daily calories are calculated: the general principle
The daily requirement is estimated as a reference point and refined by age, weight, height, and physical activity, so two people of the same weight may end up with different results.
What energy requirements depend on
- age, weight, height, and activity level — the final daily number depends on them;
- family and habits: a tendency toward overweight is often seen in families, which points to the role of genes, and the home environment often passes on eating and movement habits as well;
- sleep: those who sleep little tend to eat more and snack more often;
- emotions: eating from boredom, sadness, or stress when there is no hunger;
- medications and health: some drugs, such as steroids and some antidepressants, and conditions such as Cushing's syndrome or polycystic ovary syndrome contribute to weight gain.
The environment matters too: foods high in calories, sugar, and fat are easier to find — in vending machines, cafeterias, at celebrations — and they are often cheaper than healthier options.
Why calorie counting can be inaccurate
Even careful counting relies on average values. Energy expenditure increases with physical and mental work, psycho-emotional stress, after eating, and when temperature drops, so a calculation based on average values does not reflect a person's specific day.
When to see a doctor or dietitian
Before starting a weight-loss program, you should first consult a doctor. They can tell you what weight is healthy specifically for you and help set goals. Calorie calculation itself is not a diagnosis or a treatment.
Calorie calculation and the numbers in a calculator are not in themselves a reason to call an ambulance. 103 or 112 are needed when there is a threat to life: for example, with signs of stroke or heart attack, or with severe trauma.
This material is for reference and does not replace a doctor's consultation — the numbers from a calculator don't know your history, but a doctor does.
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This content is for reference and does not replace a doctor's consultation. Medical disclaimer