New Pill 'Helps You To Stay Fit Without Exercise'

The chemical, named after the Greek messenger goddess Iris, also helps to produce ‘healthy’ brown fat that burns off weight but largely disappears as we age. It is replaced by “bad” white fat which typically sits around a person’s waist.

Prof Bruce Spiegelman, who led the study, believes harnessing irisin will lead to better therapies for any illness that can be combated by exercise.

Prof Spiegelman said: “There has been a feeling in the field that exercise ‘talks to’ various tissues in the body. But the question has been, how?”

“Whether longer treatments with irisin and/or higher doses would cause more weight loss remains to be determined.

“The worldwide, explosive increase in obesity and diabetes renders attractive the therapeutic potential of irisin in these and related disorders.”

He added: “Another potentially important aspect of this work relates to other beneficial effects of exercise, especially in some diseases for which no effective treatments exist.

“The clinical data linking exercise with health benefits in many other diseases suggests that irisin could also have significant effects in these disorders.”

The breakthrough is an important first step in understanding the biological mechanisms that translate physical exercise into beneficial changes throughout the body, both in healthy people and in preventing or treating disease.

The researchers, whose findings are published online in Nature, said the best effects of exercise on muscle are caused by a protein known as PGC1-alpha.

They found expression of this molecule in mice stimulated another chemical called FNDC5 that is secreted as irisin in the outer membrane of muscle cells.

Experiments showed irisin is helps the ‘browning’ of white fat, which increases energy expenditure and improves resistance to obesity linked diabetes.

Relatively short treatments of obese mice with irisin improved their glucose control and caused a small amount of weight loss, which the researchers believe highlights its therapeutic potential.

According to their study, the irisin hormone has direct and “powerful effects” on adipose, or fatty, tissue – subcutaneous deposits of white fat that store excess calories and which contribute to obesity.

When irisin levels rise through exercise – or when the hormone was injected into mice – it switches on genes that convert white fat into “good” brown fat.

This is beneficial because brown fat burns off more excess calories than does exercise alone.

Only a small amount of brown fat is found in adults, but infants have more – an evolutionary echo of how mammals keep themselves warm while hibernating.

In the wake of findings, there has been a surge of interest in the therapeutic possibilities of increasing brown fat in adults.

Along with stimulating brown fat development, irisin was shown to improve glucose tolerance, a key measure of metabolic health, in mice fed a high fat diet.

Prof Spiegelman warned the discovery will not allow people to skip the gym and build muscles by taking irisin supplements, because the hormone does not appear to make muscles stronger.

“We’re not trying to replace diet and exercise. That is still important,” he added.

The study showed irisin levels increase as a result of repeated bouts of prolonged exercise, but not during short-term muscle activity.

To test whether increasing irisin alone could mimic exercise benefits, the scientists injected modest amounts into sedentary mice that were obese and pre-diabetic.

With just 10 days of treatment, the mice had better control of blood sugar and insulin levels – in effect, preventing the onset of diabetes – and lost a small amount of weight.

Although the weight loss was small, Prof Spiegelman said the hormone may have a greater effect when given for longer periods.

There were no signs of toxicity or side effects, which was predicted since the researchers limited the increase of irisin to levels typically caused by exercise.

In part because it is a natural substance and because the mouse and human forms of the protein are identical, Prof Spiegelman said it should be possible to move an irisin-based drug rapidly into clinical testing – perhaps within two years.

According to the latest government figures, more than 60 per cent of adults in England and a third of 10 and 11 year-olds are overweight.

Obesity and chronic health conditions such as high blood pressure and diabetes cost Britain £20 billion a year in lost productivity,