Tracking calories has been the traditional method to measure our energy intake, but is it actually useful?

Tracking calories is always popular, but is it actually useful?

Can the method used to measure calories become inaccurate? Read to discover!

Some people count calories to lose weight, but how accurate are we in doing so?

The fundamental principles of nutrition have for long used calories as a familiar unit of energy. The aim has always been to accurately record what was eaten and how much of it we spend in our day. It might seem simple, but it’s not. We usually tend to underestimate the amount of food we eat –I must admit I’m one of those that cheat in the calorie-tracking apps–: forgetting some meals or drinks, not being accurate with the size of the portion eaten, etc. But even if we were accurate in our records, it is not always easy to match the actual content of those foods with the data existing.

Information is often not available in labels.

The calories in labels try to quantify the metabolizable energy from food, this is not actually measured in a lab, they are calculated knowing how much energy giving the ingredients are instead. We use the Atwater factors –dating from the 1900s– which determines fat at 9kcal/gram, alcohol at 7kcal/gram, protein at 4kcal/gram and carbohydrate at 4kcal/gram. However, the amount of energy absorbed still depends on the matrix and digestibility of that food.

The amount of energy absorbed still depends on the matrix and digestibility of that food.

And even if the Atwater factors were accurate, the concept of metabolizable energy does not take into account the energy cost of digestion, absorption and transportation of the food –the thermic effect of feeding.

Energy expenditure depends on the following factors:

How difficult to quantify is energy intake?

It is extremely difficult to quantify energy intake. The errors range from recording accurately the food to the actual composition information of each food.

Calorie expenditure from exercise is difficult to measure as it depends on a lot of factors. 

If we were to measure the metabolic rate in a laboratory the margin for error could be 20-50kcal/day –pretty good. For normal people, it can be 100kcla/day or more. Physical activity is also very difficult to quantify.


To lose weight it is true that we need to eat fewer calories than you burn, but it is not always easy to measure accurately energy intake and expenditure. It is recommended to make sure the calories that you eat come from nutrient-rich foods and don’t focus only on the energy they are supposed to have.

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Peter O Brien

Peter started out his professional life as a restaurant critic but ended up moving to the kitchen, realizing that his passion didn’t only lie in tasting the food, but MAKING it. Follow his delicious recipes, as well as useful articles about the many benefits healthy and delicious food will bring to your life.+ info

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