We often hear about calories when discussing food and exercise: “How many calories does this cookie have?” or “How many calories does running burn?”. But what exactly are calories, and how many does our body need daily?
What Are Calories?
Calories are a unit of energy that the body uses to function. A calorie, when referring to food, is the energy required to raise the temperature of 1 kg of water by 1°C. This is how we measure the energy derived from food and the energy the body expends.
Energy balance is the key to good health. If energy intake from food exceeds the amount expended, the excess is stored as fat. Conversely, expending more energy than you consume leads to weight loss.
Which Foods Contain Calories?
Almost all foods contain calories, represented by the chemical energy within their composition. For example:
- A medium pizza slice contains approximately 272 calories.
- A slice of bread has 78 calories.
- An apple provides about 52 calories.
During digestion, energy from food is released and stored in molecules that the body can break down for energy when needed.
How Does the Body Use Calories?
The energy from calories is utilized in three main ways:
- Digesting food (10%).
- Physical activities (20%).
- Basic bodily functions such as maintaining heart rate and breathing (70%).
The amount of energy required varies depending on age, weight, gender, and activity level.
How Many Calories Does the Human Body Need Daily?
According to recommendations:
- Women need approximately 2,000 calories per day.
- Men require about 2,500 calories per day.
However, these figures are not fixed. For instance, athletes in endurance races can expend up to 9,000 calories/day, while older adults or those with a sedentary lifestyle may need fewer calories.
Not All Calories Are Equal
The calories in food do not necessarily equal the energy your body absorbs. Foods high in fiber, such as celery, require more energy to digest than less nutritious options like potato chips. Moreover, nutrient-rich foods (proteins, vitamins) provide greater benefits than those offering “empty calories.”
Factors Affecting Calorie Absorption
Each person absorbs calories differently, depending on:
- Digestive enzymes.
- Gut bacteria.
- Intestinal length.
This means two people eating the same amount of food can absorb different levels of energy.
Calories are a helpful tool for measuring energy, but maintaining health also involves considering food quality, exercise habits, and how the body processes energy. Choose nutrient-dense foods and balance energy intake with expenditure for a healthier body!
This content is summarized from the video What is a calorie? on the TED-Ed YouTube channel, which has nearly 5 million views. With almost 21 million subscribers, TED-Ed is one of the most-followed YouTube channels worldwide.