Death of the Calorie?

Death of the Calorie

Peter Wilson

The calorie – which comes from “calor”, the Latin for “heat” – was originally used to measure the efficiency of steam engines: one calorie is the energy required to heat 1kg of water by one degree Celsius. Only in the 1860s did German scientists begin using it to calculate the energy in food. It was an American agricultural chemist, Wilbur Atwater, who popularised the idea that it could be used to measure both the energy contained in food and the energy the body expended on things like muscular work, tissue repair and powering the organs. In 1887, after a trip to Germany, he wrote a series of wildly popular articles in Century, an American magazine, suggesting that “food is to the body what fuel is to the fire.” He introduced the public to the notion of “macronutrients” – carbohydrates, protein and fat – so called because the body needs a lot of them.

The process of storing fat – the “weight” many people seek to lose – is influenced by dozens of other factors. Apart from calories, our genes, the trillions of bacteria that live in our gut, food preparation and sleep affect how we process food. Academic discussions of food and nutrition are littered with references to huge bodies of research that still need to be conducted. “No other field of science or medicine sees such a lack of rigorous studies,” says Tim Spector, a professor of genetic epidemiology at Kings College in London. “We can create synthetic DNA and clone animals but we still know incredibly little about the stuff that keeps us alive.”

What we do know, however, suggests that counting calories is very crude and often misleading. Think of a burger, the kind of food that Camacho eschewed during his early efforts to lose weight. Take a bite and the saliva in your mouth starts to break it down, a process that continues when you swallow, transporting the morsel towards your stomach and beyond to be churned further. The digestive process transforms the protein, carbohydrates and fat in the burger into their basic compounds so that they are tiny enough to be absorbed into the bloodstream via the small intestine to fuel and repair the trillions of cells in the body. But the basic molecules from each macronutrient play very different roles within the body.