Diet by the numbers
According to Harvard calculations, a 70kg person (about the weight of the average Aussie woman) who runs at 10km/h for 30 minutes will burn 372 calories. Many people will struggle to sustain that level of effort, let alone keep up it up every day.
But you could achieve the same energy deficit just by cutting out cheeky daily snacks — a can of Coca-Cola (160 calories) and two Tim Tams in the evening (200 calories), for example — or by slightly reducing the portions of your dinner (a meal that averages about 800 calories) then having Greek yoghurt for dessert instead of high-end ice-cream (127 calories/100g vs 246 calories/100g).
So which sounds more do-able: a gruelling stint of exercise, or small changes to what you eat?
Mosley believes that understanding how many calories are in food, and how little of those calories are burned off by exercise, is an important lesson for those keen to lose weight — particularly because many of us are guilty of exercising and then (consciously or unconsciously) rewarding ourselves with food, thereby undoing the calories lost in the workout.
“If you are aware of how many calories you’re actually burning during exercise compared to what you’re taking in from food, then you may have the willpower to say, ‘No, I won’t have that 400-calorie muffin after all’,” he says.
“It makes you realise that to burn off all the calories you’re probably going to have to run for about an hour, or something like that.”
An important note about all this: exercise might not be the most effective way to lose fat, but that’s no excuse not to exercise.
“Exercise is emphatically not a waste of time,” Mosley says. “If you’re simply exercising to look at the scales then it may not be that great [but] there are so many other benefits.”
He offers a long list of them: exercise boosts mood; exercise increases blood flow around the body, especially to the brain (perhaps warding off dementia later in life); exercise cuts your risk of heart disease; exercise helps people who’ve already lost weight keep it off.
An upcoming episode of Trust Me also suggests exercise suppresses some people’s appetites, helping them control cravings — contrary to the belief that exercise makes you hungrier.
Mosley adds that when many people set out to exercise, they focus on aerobic exercise (aka cardio like running, jogging, swimming) and forget about equally important resistance exercise.
“After the age of 30 we typically lose between 1 and 5 percent of our muscle mass per decade, unless we do something about it,” he explains.
He adds that resistance exercise doesn’t have to be lifting weights in the gym.
“I do five to six minutes of resistance exercise at home every morning using my own bodyweight,” he says. “I simply do squats and press-ups and things like that.”
Saying “dieting is a better way to lose weight than exercise” is great. But as we all know, dieting can be really effing hard.
“The major problem with diets is that you feel deprived, and that’s why people find it very difficult to stick to them,” Mosley points out. “If you just cut out whole food groups then firstly, it’s not terribly good for you, and secondly, you’re not going to be able to sustain it.”
He believes the popular idea of a diet (“I need to cut out everything I enjoy and only nibble on slivers of poached chicken and steamed broccoli!”) is all wrong. Instead of eating less, he advises eating differently — citing the popular (and scientifically backed) Mediterranean diet as an example.
“The Mediterranean diet is changing what you eat but you’re not depriving yourself,” Mosley says. “It’s a relatively high-fat diet but it has enormous proven benefits.”
The best diet is any diet you can stick to, and people stick to the Mediterranean diet because it replaces “bad” stuff with satisfying substitutes: switching from hamburgers to oily fish, from saturated fats to olive oil, from sugary snacks to nuts.
Successful dieting isn’t about cutting everything out, but “switching to other forms of eating… broadly it’s a matter of changing what you eat as well as the quantities,” Mosley explains.