About Calories: What You Need To Know

What is Calorie?

A calorie is basically a unit of energy in the old metric system of units. It comes from the Latin word color meaning heat. The present unit of energy in the SI system of units is ‘Joule’. But calorie (or it’s Kilo form – Kcal) has been traditionally used and still is used for objectively specifying the energy content of the food we consume. One kilo calorie (or Kcal or Cal – note the capital ‘C’) is equal to 1000 calorie (cal – small ‘C’). Kcal /Cal is used in the context of nutritional energy content comparison.

The term calorie was first coined by Nicolas Clement in 1824 and it stands for the amount of energy required to raise the temperature of one gram of water by one degree Celsius at one atmospheric pressure. One cal = 4.2 joules and one Cal = 4.2 kilojoules.

Type of food we consume

Energy is present in the food that we eat and this energy is required for the cellular respiration functions which are continuously going on in our body. So we are actually using up calories even when lying down doing nothing! Food is mainly composed of carbohydrates, proteins, fats, vitamins, minerals, and water.

The energy composition of each category of food is different. One gram of protein gives 4 Kcal energy which is also equal to the amount of energy given by one gram of carbohydrates. One gram of fat gives 9 Kcal energy. The human body uses the energy released by these basic foods for its functioning. 20% of the energy is used for brain metabolism and rest 80% accounts for the basal metabolic needs for the other organs and systems.


The basal Metabolic rate is the energy expenditure of the body at rest to maintain the important functions of the body. It is the single largest component of total energy expenditure of the body. A lot of factors affect the basal metabolic rate – age,   fat percentage of the body, fasting state, temperature, etc. Increased percentage of lean body mass is associated with the increased basal metabolic rate. Decreased intake of food lowers the BMR as the body tries to conserve energy. BMR is also affected by certain drugs like thyroid hormone replacement, stress, illness.

# Calorie Deficit

Calories are energy. By that dictum, if we consume too much of it (more than what we expense), they will be stored in our body and we will become fat/gain weight. On an average, a man needs around 2,500kcal/day to maintain his weight and a woman needs around 2,000kcal/day.

This varies with the amount of physical activity undertaken, age, illness. Conversely, if we consume calories which are less than what we burn, we lose weight. This is called as creating a ‘calorie deficit’. Experts say creating a calorie deficit of about 500 cars is ideal to lose about 0.5 kgs/week which is considered an ideal pace for losing weight. But this also depends on the type of food from where the calories are derived.

Hidden facts

Zero calorie and low-calorie foods are not totally devoid of calories and have an inherent value of calorie present. Hence consumption of these foods, assuming they do not contribute to weight gain can be detrimental, in excess of the built-up calories from their excess consumption will get stored and lead to weight gain.

Proteins Vs Carbs

More calories are used up to digest and break down proteins than for an equivalent energy-yielding amount of carbohydrates. Thus carbs and sugars are easily broken down in our system and yield a good amount of energy, which when not burned, will lead to weight gain. Also, the carbs and sugars have low satiety index. Satiety value means the ability of the food to give us a sense of fullness/ability to counter hunger and maintain it.

High-fibre and protein-rich foods are processed slower and last longer in the stomach. This gives a sense of full stomach for a long time and thus we tend to munch far less later on. Carbs and fats bring about a surge of energy release momentarily and lead to lethargy and sense of hunger after a few minutes. Thus this leads to more consumption of food to overcome hunger and leads to weight gain. Also, intake of large meals particularly at night before going to sleep has a fat storing effect as they are not used up.

Ideal Diet

Ideally, the calorie intake should be derived from all sources i.e. carbs, proteins, fats. Roughly 60 % should be from carbs and less than 20% of a day’s diet should be fats in a normal healthy individual. Its good to start a day with foods with high satiety index – eggs, oats as these give a feeling of fullness for a longer time thereby leading to less food intake later and also are good sources of proteins and vitamins.

A whole day’s calorie intake should match the number of calories burnt to main weight. For people with lose weight, around 500 calories deficit is sufficient per day when complemented by a regular schedule of moderate exercise. In an ideal diet, one must consider avoiding having large and carbs rich food at night.

On an average, a woman must eat about 2000 calories per day to maintain a proper physique and lose 1500 calories by workout, in order to lose a pound per week. On another hand, a man must eat about 2500 calories on an average per day to maintain proper health and burn 2000 calories to lose one pound of weight per week.