A piece of wood is placed on the fire.  It burns for a certain length of time and gives off a certain amount of heat or energy.

Simple stuff.  Easy to work out how much energy it gives off, based on its size and density.  We can therefore estimate the amount of energy that type of wood will give off and work out how much of it we need to heat us up.

We can do this repeatedly with other materials.  Grass, cardboard, plastic, you name it.  Each of these will give you a reasonably accurate measurement of how much that they will give out.  Again simple.  Repeat ad-nauseum. It’s all to do with the laws of thermodynamics.

The same piece of wood gets put on the same fire, this time with some cardboard, some grass, a mattress, a few bits of laminate flooring and an old cot from the loft.

How long will the wood burn for and at what temperature?  Answers on a postcard. Even here, someone brainy enough would be able to have a reasonable stab at it and probably get close.

The same analogy goes for the way science measures the energetic output of food. Calories.  A calorie is a unit of energy.  It is not a description of a nutrient, nor is it related to nutritional value, except in the widest sense of the word.

A calorimeter measures the amount of heat (energy) that comes from a certain food.  All well and good.  But unfortunately our bodies don’t just heat food, but digest it and break it down using a complex process of chemical reactions.

The process of digestion and absorption takes variable lengths of time and is hugely dependent on a wide number of factors. The conditions that we find ourselves in, environmentally, metabolically and so forth, as well as the way in which we talk in other nutrients before and after, will significantly impact  the way in which calories are burned, if indeed the word ‘burned’ as a direct comparison to a calorimeter is even appropriate in this context.

The laws of physics in terms of energy in and out, apply only to the extent that in order to measure them accurately, you would need to take in to account the wide variety of additional factors that will influence the energetic exchange.

A recent article by Leo Benedictus in the Guardian, highlighted the nonsensical nature of such direct comparisons.  In (fairly) trying to debunk the superfood nonsenses spouted left right and centre, he made the massive error of comparing the calories in an avocado to those of a Mars Bar and those of chia seeds to a Big Mac.

It’s a bit like me affectionately slapping my partner’s bottom being likened to domestic abuse or assault.  The comparison is not only erroneous, but potentially damages and undermines the serious and real issue of domestic violence.

The comparisons of widely different food types under one misleading banner creates confusion in already confused and conflicted consumers and erodes the serious issue of obesity and diabetes.

Consumption of sugars through confectionary products and soft drinks, are contributing to a major health crisis in the UK which threatens to undermine our health service and shorten lives through type2 diabetes.  Trans fats, found in many fast foods in addition to sugar, cause heart disease in large proportions in the UK.

The consumption of raw food fats such as those found in avocados, aside from the ecological concerns are in no way part of a wide dietary concern. Not all calories are equal and should not, however convenient, be labelled as if they are.

Are calorie measurements helpful?

As with any analytical tool, information is only as good as the use to which it’s put.  Used as part of other information and within context, they can be a helpful indicator in certain limited conditions when comparing foods of similar composition. Something that is high in calories is not necessarily unhealthy because it’s high in calories.

Once the calorie gets used as a direct measurement of food across the board, the calorie not only becomes inaccurate but has the capacity to drive unhealthy and obsessive eating patterns.