Why exercise doesn't always help

Gym regimes are meant to be an extra boost to our everyday lives - making us healthier, sharper, and more youthful.

But new research by the National Institutes of Health shows it may not be as helpful as we think.

A study found mice who had one big spurt of physical exertion during the day were lazier the rest of the time.

It meant their overall physical activity leveled out, and they were barely getting any more exercise than they did before starting a gym regime.

The team led by Timothy O'Neal, a government obesity researcher, embarked on the study to understand why exercise seems to be ineffective for so many people in the US.

'Although important for overall health, exercise generally falls short on the goal of weight loss (effect size is typically less than 3 percent of body weight, even in studies lasting more than a year),' they write.

To examine the issue, they put 15 mice in a room with running wheels.

At first, the introduction of a running wheel increased daily energy expenditure in the mice.

However, this plateaued after one week, despite further increments in wheel use.

By the end of the study, they concluded the amount of wheel use did not increase their total daily energy expenditure. 

They concluded that, aside from increasing appetite, exercise may also decrease general energy - both contributing to poor weight loss. 

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