How many calories do you really need?


Food packages carry nutritional information that is based on a standard 2,000 kCal / day diet. It is important to not accept this number at face value and base your food intake on a more accurate estimation of your own calorific need. This post provides the required guidance.


The weight gain / loss equation for healthy individuals

As most of us struggling with weight gain / loss know, maintaining a constant body weight is, well, a constant struggle. The reason is straightforward: the calorie count in the food you consume is higher (or lower) than the calories your body needs.


A calorie surplus of approximately 7,700 kCal leads to a gain in weight by 1 kg in a normal healthy adult. To illustrate this:

  • 1 tsp of sugar (16 kCal) equates to body weight of approximately 2 grams
  • 1 chapati (35 grams, 92 kCal) equates to body weight of approximately 12 grams
  • 1 cup of white rice (100 grams, 130 kCal) equates to body weight of approximately 17 grams


Everything else being equal, if you drink 4 cups of tea daily with 2 tsp of sugar per cup, eliminating the sugar would enable you to lose about 0.5 kg weight in a month.


The calories you consume

Calories are provided by macro-nutrients in your food – carbohydrates (including sugar and fiber), fats and proteins. The approximate calorific content in each of these macro-nutrients is:

  • Carbohydrates, excluding dietary fiber: 4 kCal / gram
  • Dietary fiber (soluble): 2 kCal / gram
  • Dietary fiber (insoluble): 0 kCal / gram
  • Fats: 9 kCal / gram
  • Protein: 4 kCal / gram
  • Alcohol: 7 kCal / gram


For the purpose of estimating your overall calorific intake, it is common practice to ignore the calories from dietary fiber (which is a complex calculation) and instead focus on estimating the other carbohydrate, fat, protein and alcohol content of your diet.


The calories you need

Estimating the calories your body requires can be broken up into three steps:

  • Estimate your Basal Metabolic Rate (BMR) – the calories required by your body to maintain its core metabolic functions. This is influenced by your gender, age, height, weight and certain environmental conditions such as temperature
  • Estimate your Active Metabolic Rate (AMR) – a multiplier applied to the BMR, linked to the level of activity and exercise you undertake
  • Estimate additional calorific requirements for special needs, such as pregnancy and lactation


The Basal Metabolic Rate

The Harris-Benedict formula is used to describe BMR as a numeric value, calculated as follows:

  • BMR for Women = 655.1 + (9.563 x weight in kg) + (1.850 x height in cm) - (4.676 x age in years)
  • BMR for Men = 66.47 + (13.75 x weight in kg) + (5.003 x height in cm) - (6.755 x age in years)

It must be remembered that the above formula has been found to be accurate to 90% levels in about 60% of the population, and is therefore not foolproof. However, this is the most widely accepted measure for BMR.


The Active Metabolic Rate

The AMR is a multiplier applied to the BMR, linked to the level of activity performed:

Level and intensity of activity

AMR multiplier

Sedentary: You work at a desk job and you don't do much housework, walking, or exercising


Lightly active: You don't exercise much, but you go for walks 1-3 times per week and are on your feet doing housework during some of the day.


Moderately active: You exercise 3-5 times a week and stay moving throughout the day with non-exercise activities.


Very active: You exercise intensely or play vigorous sports on most days.


Extra active: You exercise intensely or play vigorous sports nearly every day, including occasional "two a days." You also work a physical job or are on your feet most of the time.



Additional calories in special situations

Certain special situations increase the requirement of calories – these include:

  • Pregnancy: 300 kCal / day
  • Lactation: 330-400 kCal / day


Curious about your daily calorific requirements? Use this calculator.

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