Exploring the myth of irisin: does this weight-loss hormone exist?

Every now and then the fitness scene is rocked by a new discovery that promises to rewrite the rules of weight loss and to solve virtually all problems caused by excess pounds. A couple of years ago the HCG diet was considered a revolutionary approach to weight loss, but everybody seemed to forget that the amazing weight loss strategy was based on hormone injections and drastic calorie restriction.

These days, the gluten free diet and HIIT workouts seem to be the most appreciated solutions for weight loss, but about 4-5 years ago, a new discovery was making the front pages of health websites and magazines: irisin, a relatively unknown hormone, was being introduced to the public as the new Holy Grail of weight loss.

What is irisin and what does it do?

Irisine is a myokine produced by skeletal muscles, which helps muscle cells take in glucose, stimulating metabolism. Some studies found this chemical to increase energy expenditure and to encourage the conversion of white fat to brown fat, concluding that irisin may be a powerful weight loss agent.

For those of you who aren’t familiar with brown fat, I’ll quickly explain what this fat is and how it affects the human body. Brown fat is a type of adipose tissue found inside the body, mainly in the neck and shoulder areas, which is present in higher amounts in babies and decreases with age. Unlike white adipose tissue, which stores excess calories for later energy production, brown fats use white lipids to generate heat and produce energy.

Brown adipose tissue is activated by exposure to cold temperatures and by shivering, so if you want to kill two birds with a stone and to accelerate the fat loss process, you should exercise at lower temperatures and sleep in a cold bedroom. This would boost your metabolic rate and the production of irisin, therefore would make it easier for your body to burn impressive amounts of fat without having to change your workout routine or diet habits.

The activation of BAT, which can speed up weight loss, isn’t the only beneficial effect of irisin, scientists suggest. Dr. Bruce Spiegelman and his colleagues from the Dana-Farber Cancer Institute and Harvard Medical School showed that this hormone may impact one’s health in several ways. According to their studies, irisin may stimulate the growth of neurones and improve cognition, may slow down the aging process, and may help fight diabetes, obesity and Parkinson’s disease.

But what if the existence of irisin is only a myth, as other researchers say? Harold P. Erickson, Ph.D., professor of cell biology and biochemistry at Duke University School of Medicine, has co-authored a study that suggests that irisin doesn’t exist, and that the positive results obtained by previous researchers were based on contradictory and invalid data.

Activation of brown fat, supported by studies

With or without irisin, the existence and activation of brown fat is supported by research. A recent study published in the Cell Metabolism journal showed that brown fat cells receptors can be activated with certain drugs, leading to an increase in the brown adipose tissue metabolism. The metabolic rate increased with 203 calories per day, without changes in diet or physical activity.

Systolic blood pressure and the heart rate were also elevated, showing that the drug can stimulate the cardiovascular system. However this method of activating the brown fat requires more research, as the participants only received one dose of the mentioned drug.

Exposure to prolonged stress and severe burns are also listed as activators of brown fat cells, scientists showing that adrenaline-inducing stress may encourage the conversion of white fat into brown adipose tissue.

But the safest and more convenient method for stimulating BAT and boosting the fat burning process remains exposure to low temperatures. Spending several hours in mild cold can activate the brown fats, increasing the resting metabolic rate and energy expenditure by 15%.

Thanks to its ability of improving blood glucose levels and supporting the destruction of white adipose cells, activation of brown fat could be a safe and accessible solution for obese people and diabetes sufferers.

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