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noun [uncountable]

a hormone (= a chemical substance produced in the body) which can reproduce the health benefits of exercise and a good diet

'Scientists at Dana-Farber Cancer Institute have isolated a muscle hormone which may be responsible for the many health benefits of exercise. The scientists have named the hormone irisin after the Greek messenger Goddess, Iris.'

The Atlantic 20th January 2012

Imagine having access to all the weight-loss benefits of a regular workout at the gym, without needing to move a muscle? If, like me, you're a little bit allergic to regular exercise and worryingly fond of 'naughty' foods, you might be interested to know that there's a newly identified hormone out there which could allow people, quite literally, to 'have their cake and eat it'. Researchers are now looking carefully at a substance called irisin, which, they claim, can simulate the health benefits of regular exercise and a sensible diet.

scientists are warning that use of irisin isn't intended to be a substitute for a healthy diet and exercise

Irisin is a hormone naturally found in muscle cells, and it increases in the body when we take exercise, boosting the amount of energy we expend and controlling blood sugar levels. This hormone also has the benefit of helping convert bad, calorie-storing 'white fat', which typically sits around a person's waist, to good, calorie-burning 'brown fat', which is found in babies and young children but largely disappears when we become adults. Brown fat is particularly beneficial to health because it burns off more excess calories than exercise alone.

Scientists have demonstrated irisin's effects by injecting it into overweight mice, which were fed a high-fat diet and had no exercise. Within a period of ten days, the mice lost a small amount of weight, and in theory could have lost more if it had been given for a longer period. They suffered no other side effects since the amounts administered were only at a level consistent with what would be produced by exercise. Because irisin is a natural substance found in both mice and humans, researchers say it should be possible to move very quickly to clinical testing, perhaps in as little as two years.

Research seems to therefore suggest that irisin could provide people with all the benefits of exercise without the need for any kind of exertion. However, before the couch potatoes among us have the chance to get too excited about this, scientists are warning that use of irisin isn't intended to be a substitute for a healthy diet and exercise. Its potential application is, rather, directed towards tackling extreme obesity, diabetes and other disorders where exercise would benefit patients who are too weak to engage in it.

Background – irisin

The identification of the new hormone irisin occurred in connection with research undertaken at Harvard Medical School in the USA, led by cell biologist Dr Bruce Spiegelman.

Scientists named the hormone, which is a protein acting as a chemical messenger from muscle to fat tissue, after the Greek goddess Iris, who is traditionally associated with messages and communication.

The suffix -in is commonly used in the formation of names for chemical substances, proteins, etc. A well-known comparative example is insulin, formed from Latin insula, meaning 'island', and referring to a glucose-controlling hormone produced in the pancreas by special 'islets'.

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This article was first published on 30th January 2012.

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the phenomenon by which an incompetent person is too incompetent to understand his own incompetence

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