Are calories important?

Edited excerpts from the Observer Food Monthly collaboration with Dr Ali Khavandi and Dara Mohammadi

140 calories of cola versus 140 calories of broccoli

Watch the antiques roadshow for all of five minutes and you’ll notice something unmistakable about man: we love to ascribe value to things. It helps us signpost and make decisions about an otherwise incomprehensible jumble of information, like the way we use calories to help us manage what we eat.

The concept entered public consciousness during the First World War when the state, like a miserly auntie, used it to make sure people didn’t over eat during food scarcity. The calorie is a measure of energy needed to heat one cubic cm (gram) of water by 1°C and the kilocalorie (‘large’ calorie used in food = 1000 ‘small’ calories)— has since become the backbone of our understanding of healthy eating, but at what cost?

In a perfect world of bad science it makes perfect simple sense. If you consume more energy than your body needs then according to the central tenant of Einstein’s most famous equation it’ll be turned into mass — a wibbly wobbly type of mass around your belly and thighs. [This was meant to be a tongue-in-cheek illustration of some of the crazy extrapolation of respected scientific principles to justify pseudoscientific dietary beliefs but clearly got lost in translation/ was a little too subtle within the 400 word limit of the published article!]

The problem is that our bodies don’t burn energy with the consistency of a Bunsen burner and the food we consume is more than just a simple, consistent ‘fuel’ in terms of physiological response. “We do not absorb all the nutrients from some foods,” says Pete Wilde, a researcher at the Institute of Food Research in Norwich. “By chewing and eating whole almonds, for instance, we absorb only around two thirds of the energy listed on the label. The calcium in milk and dairy products reacts with fatty acids and again reduces the energy absorbed.”

The different rates of digestion of different foods can also affect your appetite. “The more slowly our food is digested the less hungry we’ll feel for longer,” Wilde adds. “The calories absorbed by two different foods could be the same, but if one food is digested more slowly then it’ll make us less hungry and less likely to snack between meals.”

In how your body uses — and stores — energy, 140 calories of cola is not the same as 140 calories of broccoli. If you want to lose weight by starving yourself, then a calorie-restricted diet is the way to go. Though you’ll likely bounce back once you start to eat normally, whatever your normal was. If you’re after a sustainable way to be healthy it’s best to think a little more about the constituents of your food.

A healthy diet is not about restriction but inclusion of diverse and protective foods. Choosing food on the basis of only calorie content is like choosing your life partner on how quickly they can run 100 metres: it might be useful in extreme circumstances, but for your day to day life and general wellbeing, it’s pretty much useless.

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