Move more and you can enjoy that extra slice of cake or
second drink. Or so we’ve been led to believe. The evidence suggests that it’s
not quite that simple.
Building up a sweat at the gym can feel good. You’re on a
quest to lose weight and your workout will burn up plenty of kilojoules. But
this message is misleading, and it can cause your motivation to wane if your
weight isn’t decreasing as quickly as you’d hoped.
Here are some facts about exercise, and why it may not be
the quick fix for weight loss that we once believed.
FACT: Exercise alone can’t create a big energy deficit.
The process should be fairly straightforward. Exercise more,
burn kilojoules, develop an energy deficit and lose weight.
Except it isn’t quite that simple.
While your food intake accounts for 100 per cent of the
energy that goes into your body, exercise only burns off less than 10 to 30 per
cent of it. Your basal metabolic rate (energy needed for basic body functions)
accounts for 60 to 80 per cent of total energy expenditure.
If a 90-kilogram man added 60 minutes of medium-intensity
running four days per week while keeping his kilojoule intake the same, and he
did this for 30 days, he’d lose just over kilograms, calculated Dr Kevin Hall
of the US National Institutes of Health.
“If this person then decided to increase his food intake, or
relax more to recover from the added activity, then even less weight would be
lost,” says Dr Hall.
If you are overweight or obese and trying to lose a large
amount of weight, it would take lots of time, effort and willpower to make a
real impact on kilojoule deficit through exercise alone.
FACT: You can’t outrun a bad diet.
For many years we’ve believed that lack of exercise and
excess kilojoules are equally to blame for the current obesity crisis. Many
researchers disagree, with some claiming in the British Medical Journal
that “you can’t outrun a bad diet.” They blame our expanding waistlines
primarily on our food choices, stressing that where the kilojoules come from is
as important as the number.
Poor diet does more than add weight. According to The
Lancet global burden of disease reports, poor diet is responsible for more
disease than physical inactivity, alcohol and smoking combined. You can be
active every day, but it won’t negate the effects of an unhealthy diet.
FACT: Exercise is the world’s best drug.
This doesn’t mean you should give up exercise. There are
many reasons to move more beyond weight loss. “It’s probably the single best thing
you can do, other than stopping smoking, to improve your health,” says Dr Hall.
Upping your activity levels will reduce your risk for
chronic diseases including heart disease, stroke, type 2 diabetes, dementia and
certain cancers. It will support your immune system so you can better fight off
illness; improve your sleep quality, fitness and mood; and protect against
depression, anxiety and stress.
And while exercise may not help us lose a lot of weight on
the scales unless we address diet too, studies have shown it’s essential for
keeping weight off and preventing weight regain.
As a bonus, regular exercise changes our dietary habits,
which means we’ll have an easier time making healthier food choices.