A 1200-kilojoule doughnut is not the same as a 1200kJ chicken thigh. But you knew that, right? Of course you did.
Doughnuts spike blood sugar and leave you hungry, while chicken provides tons of muscle-building, hunger-fighting protein. Yet outside of fitness magazines and CrossFit boxes, nutrition conversations rarely go deeper than kilojoules. Kilojoules are posted on fast-food restaurant menus and stamped on packaged foods. They’re ticking away on fitness trackers and adding up in smartphone apps. They’re like the Kardashians of nutrition – confusing and overrated, yet completely inescapable. And every time you see them, you’re probably being fed misinformation.
Take nutrition labels: when it comes to kilojoules, those labels can be misleading. Why? Because they presume all kilojoules are the same. In fact, your body handles kilojoules differently depending on their source. As for exercise and lifestyle, studies show that fitness trackers don’t always count kilojoules correctly, that the gym may not be the best place to burn them, and that those late nights at the office (and lack of sleep afterward) can pad your waist more than your wallet.
We’d bet there are at least six things you don’t know about kilojoules – and that lack of knowledge could be weighing you down.
1/ Your Fitness Tracker Has A Counting Problem
In a 2014 study from Iowa State University, scientists asked 60 people to strap on one of eight different fitness trackers then complete an hour-long workout. Afterward, they compared each tracker’s results to the participant’s total oxygen consumption – a trusted measure of kilojoule burn. The verdict? Every tracker they tested was off by between nine and 23 per cent.
USE YOUR PHONE Researchers at the University of Pennsylvania found that apps like Moves and Health Mate showed less variability than wearable devices when tallying step counts, which is what most kilojoule estimators use to calculate how much you burn.
2/ “Nutrition Facts” Labels Are Far From Accurate
The kilojoule stats on packaged foods are based on a 100-year-old formula and can be up to 25 per cent off, says Rachel Carmody, a postdoctoral fellow at Harvard. The true energy content of a food may be lower than what’s on its label, thanks to its “thermic effect” (the energy required to digest it). How much lower depends on how your body works to process it.
EAT MORE PROTEIN Meats and vegetables make your metabolism burn hottest, delivering 20-30 per cent fewer kilojoules into your system than more easily digested simple carbs like pasta and ice cream. Limit simple carbs to less than 10 per cent of your total intake.
3/ Antibiotics Might Inflate Your Kilojoule Intake
We’re not talking about what your doctor prescribes. We’re referring to what you buy from the butcher. Antibiotics given to livestock can skew the balance of bacteria in your gut, nurturing a microbiome that’s more efficient at pulling kilojoules from food and shuttling them into your body, says Carmody.
GO ORGANIC In addition to eating antibiotic-free meat, dairy and fish, stock up on vegetables and whole grains. “A fibre-rich diet nurtures microbes that aren’t as efficient at extracting energy,” says Carmody. If you’re trying to lose weight, that’s a good thing.
4/ The Processing of Food Unlocks More Kilojoules
You already know that a double-choc muffin is no friend of weight loss. But any kind of processing – including juicing, grinding, milling and cooking – breaks food down, rupturing cell walls and reducing the energy required for digestion. “Not only does processing make it easier to extract kilojoules, but also fewer of them are excreted,” says Carmody. The result is more kilojoules entering your body and staying there.
STOCK UP ON WHOLE FOODS More than 75 per cent of the kilojoules we eat are from moderately or highly processed foods. Only a quarter come from whole or minimally processed foods. Your goal: reverse the ratio. Focus on single-ingredient foods, like fish and fruit.
5/ You Can Burn More Kilojoules Outside the Gym
If you’re an 80-kilogram man, your vigorous 30-minute strength workout will burn about 1030kJ. That’s good – but it’s still only a fraction of what you burn each day through non-exercise activity thermogenesis. Indeed, the cumulative kilojoule burn of everyday pursuits like brushing your teeth and playing pool after work with your mates is far greater than anything you can hope to achieve in the gym.
STOP SITTING AROUND “You have the ability to increase your burn by as much as 4200kJ a day by spending more time in motion,” says Dr James Levine, a professor of medicine at the Mayo Clinic. Check out “Boost Your Burn” (below) for six ways to do just that.
6/ Skipping Sleep Makes You a Kilojoule Vacuum
In a University of Colorado study, guys who were restricted to five hours of sleep a night ate six per cent more kilojoules a day. That alone was enough to pack on a kilogram over a five-day period. And according to study author Kenneth Wright, sleep-deprived men are also more likely to binge on carbs and high-kilojoule snacks after dinner – habits linked to weight gain.
HYPNOTISE YOURSELF When you hit the sack, imagine yourself repeatedly teeing off on your favourite par 3. “Visualisation reduces anxiety and lets your brain’s sleep mechanism engage,” says sleep medicine expert Dr W Christopher Winter.
BOOST YOUR BURN
6 gym-free ways to torch nearly 3000kJ more every day
303 – Biking to work for 40 minutes instead of driving for 20 minutes
82 – Joining a 30-minute conference call on your mobile and walking instead of staying put at your desk
29 – delivering 15 messages in person rather than by email
70 – Sacrificing half an hour of screen time to walk the dog
123 – Trading 45 minutes of TV-watching to help tidy up the house
50 – Having sex for 20 minutes before going to bed
2760 – Extra kilojoules burned (calculations are for a 80kg man)