But what is the role of muscle training in the action of this abnormality in one of the most important and multifunctional organs of our body, the heart?
This question motivates the research of Brazilian researchers from Unicamp (State University of Campinas) and USP (University of São Paulo) in partnership with colleagues from universities at the Faculty of Pharmacy and Health Sciences in Harvard and Massachusetts, USA. This study was published this month in the international journal Journal of Endocrinology and is supported by Fapesp (the Foundation for Research Support of the State of Sao Paulo).
Experiments with mice show that 15 days of moderate strength training is enough to reduce fat accumulation in the liver and improve glucose control in the body. This is the first time a study has shown the specific effects of muscle training – not aerobic exercise, such as walking and jogging, for example – in this organ.
To understand this discovery and what it can represent in our daily lives, we must first understand the parts of the body involved, its function – and dysfunction.
Fat you can't see
When you think of fat, you can immediately think of what you see: in the stomach, on the arm, at the foot …
However, it also accumulates in organs. And the liver, which has been known to ensure excessive consumption of alcohol and food, also suffers from the presence of abnormal fat in it – which is toxic to organs.
"Everyone has a little fat in the liver, but when there is accumulation and it's not treated, the condition can develop into inflammation, steatohepatitis. If you continue not to treat it, it can even develop into cirrhosis, more extreme cases, carcinoma (malignant tumor), "Leandro Pereira de Moura, a professor at Unicamp and research coordinator, told BBC News Brazil.
That is why the liver is affected by obesity and also with type 2 diabetes (which is associated with obesity and sedentary lifestyles, which usually affects people over 40 – even though it affects people earlier and earlier).
This is now a condition that represents some of the most serious and growing health risks in the world for the population. According to the WHO (World Health Organization), in 2016, 13% of adults worldwide were obese; in relation to diabetes (both types), in 2014, reached 8.5% of them.
And this disorder is still correlated: according to the British organization Diabetes.co.uk, it is believed that obesity accounts for 80 to 85% of the risk of developing type 2 diabetes. Some studies have shown that obese people have 80-fold. more likely to develop this disease.
But how does diabetes 2 – which is involved in this study – directly affect the heart?
Diabetes is a disease that is manifested by problems in the production or effect of insulin, a hormone produced by the pancreas that allows glucose to enter the cell to convert it to energy.
The liver is one of the main organs involved in the management of sugar in the body. This is because "storing" glucose, which is released when the liver responds to insulin. This is proven, for example in fasting, because it is the organ that guarantees several hours of "fuel" for the body without food.
"The pancreas secretes insulin, but it acts in various ways in the body, for example, in the brain, it can control shape, and in the muscles, it makes glucose absorption. In the liver, the action of insulin has just released and stopped glucose production," Moura explained , who conducted a postdoctoral study at Unicamp in partnership with the Harvard School of Public Health.
"When fat is toxic to the liver, the body fails to respond to insulin properly, so people who are obese and diabetic have an image of insulin resistance, which means they have hormones but the body does not respond well.
Role of training
Thus, reducing the presence of fat in organs is fundamental for patients such as obesity and diabetes.
But how do you do it?
Because the effects of weight loss and aerobic exercise in removing fat throughout the body are well known, Moura and his team decided to test the role of strength training especially in the heart.
Because they wanted to know the role of muscle activity, they tested guinea pigs to ensure there was no weight loss.
Mice, manipulated under Brazilian legislation and evaluation of the Unicamp ethics committee regarding animal research, were divided into three groups: the control group accepted a standard diet and did not exercise; others receive a high-fat (35% fat) diet and don't exercise too; the last group also did a hyperlipidic diet but, when they had become obese and diabetic, they did strength training for 15 days.
At the end of the test, this group (guinea pigs who underwent exercise) were still obese, but had normal fasting blood glucose levels; also experienced a 25-30% reduction in liver fat. On the other hand, sedentary obese sufferers still suffer from diabetes.
Now, the researchers' next step should include testing with humans and looking for details about how the positive effects of muscle training occur. According to Leandro Moura, the key to this is the role of certain proteins that we have in the body.
"When they are released into the body, they act in different organs: the brain, liver, lungs," he explained. "A role called & # 39; exercise & # 39 ;, proteins released into the blood during physical exercise are being investigated.
Finally, by confirming the properties of this protein, the team even glimpsed their synthesis, turning it into a drug, for example. But, said the researcher, even if this drug appears, physical activity will still be fundamental.
"We are far from understanding the full functionality of physical training. We not only have biological but psychological effects, etc. We cannot summarize all this in a capsule," said professor Unicamp.
BBC Brazil News – All rights reserved. All reproductions are prohibited without written permission from BBC News Brazil.