Australasian Science: Australia's authority on science since 1938

The Fit

The Truth about the Average Adult Energy Intake

By Tim Olds

Nutritional labels on food state that the average adult consumes 8700 kJ/day, but isn’t this a bit low?

The Tour de France is an extraordinary sporting event, with some of the world’s fittest men embarking on a challenge that is on the very edge of human endurance capacity. This year 198 cyclists set out to cycle 3664 km in 21 days.

I often watch the Tour with a bottle of beer, the label of which tells me that it contains 6% of the “average adult diet” of 8700 kJ. But where does this figure come from? How do we know how many kilojoules a person consumes or needs?

We Built It: They Didn’t Come

By Tim Olds

A global report gives a gold medal to Australia’s community sporting facilities yet finds that our kids are the second-least active in the world.

It’s “active break” time, and up on the stage a dance instructor is telling us to move in our own “bubble of awesomeness” as conference delegates at the Global Summit on the Physical Activity of Children in Toronto make some rather awkward and even absurd attempts at dance moves. I can’t seem to locate my own bubble, so I thought I’d nick out and update you on the first Global Report Card on the Physical Activity of Kids (

Belief Beyond Evidence, Evidence Beyond Belief

By Tim Olds

Will the childhood obesity epidemic condemn young people to a shorter lifespan than their parents?

When I was born in 1955, life expectancy for Australian males was 67. Now it’s almost 80. Around the world, with very few exceptions, life expectancy is increasing at the rate of about 2.5 years each decade, and has been doing so for at least 150 years. So I was indeed surprised when I first read this in 2005:

“If we don’t get this epidemic of childhood obesity in check, for the first time in a century children will be looking forward to a shorter life expectancy than their parents.”

The Truth about Screen Time and Kids’ Health

By Tim Olds

A number of health outcomes have been attributed to the amount of time children spend in front of screens, but look a little deeper and a different picture emerges.

The average Australian adolescent spends about 4 hours each day in front of a screen of some sort. A typical home now has three TVs, three laptops and two videogame consoles, and kids’ bedrooms resemble electronics display rooms. About one-third of Australian kids aged 9–11 have a TV in their bedroom (that’s only half of what we find in the US).

Being Physically Active Became Twice as Hard

By Tim Olds

How much exercise do we need to remain healthy? A group of experts has now upped the ante dramatically.

The last Australian Physical Activity Guidelines were in 2004, when it was recommended that adults get 30 minutes of exercise five times per week. In February the new guidelines were published, with the Australian government now recommending that we get 60 minutes of exercise five times per week. We also need two muscle strengthening sessions, and we need to reduce our sitting.

A 100% increase seems a bit beyond the normal rate of inflation, especially given that about half of all Australian adults didn’t get even 30 minutes per day. So how do experts decide on these guidelines?

Health through Housework

By Tim Olds

We do more vigorous exercise through housework than walking, but is it enough to keep you in shape?

I was skeptical, and my wife’s case wasn’t helped when I discovered that in Nazi Germany the women’s organisation, the Frauenschaft, sponsored a “Health through Housework” movement that combined household chores with Swedish gymnastics. Picture making the bed standing on one leg and you’ve pretty much got the idea. But she persisted: “Really, dear, you complain about the housework but science tells us it’s actually good for you.”

Mapping Happiness

By Tim Olds

Blogs, tweets, news reports and songs can be used to map happiness levels by city, age group and even the day of the week and the time of the day.

Happiness is good for us. Happier people have stronger immune systems, better mental health, live longer lives, earn more money and are more likely to have stable marriages.

These associations are enduring. One study found that people who were happy in their first year at university had higher salaries 16 years later, even when allowance was made for initial wealth differences.

When Can Weight Loss Be Dangerous?

By Tim Olds

Unless they are extremely obese to start with, people who lose weight die younger.

If you’re overweight or obese – and that’s about 60% of us – then losing weight will improve your blood pressure, blood fats, blood glucose levels and insulin sensitivity. Weight gain has the opposite effects.

The Science of Sitting

By Tim Olds

Sitting for extended periods increases mortality, but is it worth working at a treadmill desk?

The average adult Australian spends about 9.5 hours each day on his or her derrière, about 7.5 hours asleep, about 6.5 hours standing or moving around slowly, and about half an hour walking briskly or exercising.

What do we do in those 9.5 hours of sitting? We spend 3 hours watching TV, 1.5 hours on the computer, an hour eating and another hour travelling, we read for an hour, sit and talk for an hour, plus spend an hour just chilling.


By Tim Olds

We are walking less than ever, but urbanisation isn’t always to blame.

When did you last go for a walk? A really long walk? We used to walk more than we do today. Today, the average Australian walks for about 40 minutes per day, and that includes walking to the shops or walking from the car to the office. Daily walking time increases from 24 minutes for 10-year-olds, peaks at 54 minutes when we are in our 40s and 50s (the work years), and then falls back to 24 minutes again in our 70s. Hunter-gatherer groups like the Ache and !Kung walk 2–4 hours each day.