They’ve been the linchpin of weight loss since, well, forever, but new studies suggest that the way we measure calories is completely flawed.
You order a juicy rib-eye and the waiter asks how you want it have. The only factor in choosing your steak’s sear level is taste, right? Apparently not. New studies suggest deciding for medium-rare over well-done could make a difference to the number of calories your body gets. Until now, calories have been the one constant in the fluid world of weight loss, but it turns out they’re not as accurate as we thought. How food is processed is intrinsically connected to both how we digest it and the amount of energy our body uses from that food. This means that the calorie content splashed across thousands of food labels is inaccurate.
Due to growing research, we have a new understanding of what we get out of food. Does this mean the era of the calorie is over for good? To look forward, we must first look in the past; the science behind calorie counting is old. Developed by US chemist Wilbur Atwater in the late 19th century, he burned individual foods and measured how much energy they gave off. Then he estimated the percentage of this energy the body actually used by calculating the energy left over in undigested food. Yep, Atwater was scrutinizing faeces a century before Gillian McKeith.
What did he discover? Four calories in 1g protein, nine in 1g fat, four in 1g carbs and seven in 1g alcohol. Years later, it was discovered 1g fibre has two calories. Although taken as gospel by doctors, food companies and the public alike, Atwater’s system is facing ever-growing condemnation.
During the 2013 annual meeting of the American Association for the Advancement of Science, a group of nutritionists warned calorie figures on food labels could be wrong by up to 30%. Their issue? Traditional calorie counting gives no credence to cooking, processing or digestion.
When food is cooked, the heat causes its molecules to separate, making it easier for digestive enzymes to process them. As a result, your body takes up the full amount of calories available. A study discovered that mice fed cooked food gained as much as 30% more fat than those fed exactly the same food, however in its uncooked state.
How much calories?
The science behind their theory does make sense. Take a plate of carbs, made from starch, which itself is a chain of closely linked sugar molecules. Eat them as is and they pass through your system and out the other side, with your body only holding onto about two-thirds of their calories. Cook it, and the starch grains open up, making it easier for digestive enzymes to do their work, which gives your body more energy and calories. Understandable?
There’s more. That same cooked food provides fewer calories once it’s gone cold because the natural cooling process makes starch crystallize into structures too complicated for our digestive enzymes to easily break down. So that covert serving spoon of leftover pasta bake on the way to bed isn’t quite as bad as you thought. Heat isn’t the only thing to cloud the calorie-counting issue. We expend energy during the digestion, but this differs from food to food, depending on how complex its molecules are.
A 2010 study found people who ate wholewheat bread with cheddar used up double the energy than those that ate the same quantity of white bread and processed cheese. The result? The wholewheaters netted 10% fewer calories than their white-bread-eating counterparts. Don’t swear off your saucepans just yet though – the experts aren’t saying we need to turn raw, we just need a new system. It factors in the energy we use when digesting fat, carbs, protein, and fiber.
NME represents the number of calories available for your body in food, after the calories used in digestion have been subtracted. When broken down, the numbers look like minor adjustments, but consider this, for example, we do indeed absorb four calories per 1g carbs, the number of calories in protein is more like 3.2, meaning a protein-based meal may actually contain almost 25% less calories than we think it does. Instead of counting calories, a traffic-light system on food labels could be a more accurate measurement for tracking your diet, where green indicates unprocessed foods, red means it’s extremely processed and amber is in the middle. Another potential alternative is to turn away from calories altogether and concentrate on the extent to which a food could make us feel full, a popular idea among British researchers.
“How satiating a person believes a food to be influences how much they eat and as a result, that impacts their energy intake,” says Professor James Stubbs, who’s working with Dr Nicola Buckland and Dr Graham Finlayson of Leeds University to create a satiation index in conjunction with Slimming World, which they believe will be a more accurate weight-loss tool than calorie counting.
Speeding up satiation and suppressing appetite
In the meantime, the University of Liverpool is leading a £6million, EU-funded project to determine which ingredients and processing strategies of food components (carbs, fat, proteins) and types (bread, diary, fish) speed up satiation and suppress appetite. Despite the evidence that there’s a better alternative to traditional calorie counting out there, not everybody is convinced there’s a need for a complete reform.
Food labels should be read as a guide, so there’s no need to be accurate to the last calorie. Weight management comes down to a more general understanding of calories and portion sizes. An extra bite or two of cake will have far greater impact on the calories absorbed than subtle differences in digestion and absorption.
One thing we do know for certain – the way we currently use calories isn’t an accurate guide for people who want to lose or maintain a healthy weight. If you’re trying to shed pounds, try to eat all your snacks raw and process meals as lightly as possible, such as through steaming. And keep in mind that eating cooked foods cooled down makes a difference to the calories you’ll gain, so go for cold, leftover wholewheat pasta for lunch, rather than a shop-bought hot wrap.