Australasian Science: Australia's authority on science since 1938

Biggest Loser Provides Food for Thought

By Tim Olds

Contestants on The Biggest Loser have provided some startling evidence explaining why it’s difficult to keep weight off after dieting.

The full text of this article can be purchased from Informit.

About two-thirds of all the energy a human body uses does nothing but stoke the internal furnace – keeping a consistent body temperature, the blood going, the lungs blowing, and the juices flowing.

Resting metabolic rate (RMR) is the rate at which we use energy when we’re sitting or lying down doing nothing (fasted, naked, in a thermoneutral room, as you do). We humans are not exactly powerhouses: we only generate about 80 W, and about half of that is used to keep the brain and liver working.

There are two main ways RMR can be expressed: in absolute terms (as a certain number of kilojoules per day, or litres of oxygen consumed per minute) or in relative terms (kilojoules per kilogram of bodyweight per day, or litres of oxygen per kilogram per minute). Because the main thing driving RMR is the amount of fat-free mass we have, RMR is often expressed as kilojoules per kilogram of fat-free mass.

Other than fat-free mass, a lot of things can affect resting metabolic rate. In relative terms it decreases as we get older. Hormones such as thyroxin can turn up the thermostat.

The genetic lottery plays a role. After adjusting for age, sex and fat-free mass, about 40% of the variance in RMR can be put down to genes.

Now, two recent studies on RMR have really put the obesity cat among the metabolic pigeons. One study followed contestants on the...

The full text of this article can be purchased from Informit.