Japan runs the risk of confronting an obesity problem
Gradual changes by young people in recent years to the Japanese traditional diet pattern means that the country is beginning to exhibit increased childhood-adolescent obesity rates, according to Unicamp researcher
By Elton Alisson, in Tokyo
Agência FAPESP– Changes affecting world dietary patterns starting in the 1950s – when the large food industries began to develop technologies that improved food production, but also led to the increase in the amount of saturated fat in the diets of populations in a number of countries – has caused obesity to become an epidemiologically important disease worldwide.
One of the countries where obesity rates are still below the world average, Japan, now runs the risk of also confronting the problem of the population’s increasing weight. This is because in recent decades, traditional Japanese eating patterns have changed, especially with the adoption of fast food.
“Today, Japan is seeing increased childhood-adolescent obesity rates, although they are still below those in the United States or Brazil, mainly because the aging population has been able to maintain traditional Japanese dietary patterns that value the consumption of fish and vegetables,” Lício Augusto Velloso, professor in the School of Medical Sciences at the State University of Campinas (Unicamp), told Agência FAPESP.
“But the Japanese are concerned about this phenomenon because once the children and adolescents become accustomed to a dietary pattern, it is very hard to go back to the traditional style of eating,” he stated.
The researcher gave a lecture at the Japan-Brazil Symposium on Research Collaboration. Jointly organized by FAPESP and the Japan Society for the Promotion of Science (JSPS), the event was held March 15-16 at Rikkyo University with support from the Embassy of Brazil in Tokyo.
According to Velloso, what was believed, rather simplistically, until recently was that due purely to the fact that saturated fat has a very high calorie content, just the ingestion of large amounts of fat by eating processed foods would cause obesity.
What the research team that coordinated the study found, however, was that the consumption of excess saturated fat also causes inflammation in the hypothalamus, which causes the neurons in this part of the brain – which control hunger and the human energy balance – to work in an anomalous way. As a result of this, obese people lose the ability to adequately control hunger and end up eating even more.
The discovery made within the scope of a research study supported by FAPESP was published in a 2005 issue of the journal Endocrinologyby the American Endocrine Society.
“This was the major breakthrough we made in recent years in research into the causes of obesity and it showed how fat – not only because it is rich in calories, but also because it promotes neuron damage – contributes to making people become increasingly obese,” Velloso emphasizes.
According to the researcher, since it is very rigid, saturated fat is able to develop inflammation in several tissues, including the human brain.
The organ, however, is a highly differentiated cell that is also very sophisticated from the biological standpoint. Any inflammatory process, no matter how slight, in the region where neurons that control hunger are located, end up affecting how brain cells work.
“When inflammation in the hypothalamus is caused by the excess consumption of saturated fats, the neurons are unable to produce neurotransmitters, which are needed to control hunger,” Velloso explains.
Prolonged fasting causes the neurons to produce a neurotransmitter called NPY which, available in large quantities in the hypothalamus, causes hunger.
When the hunger is satisfied, the human brain receives a message from several “senders” – such as the stomach itself and the nutrients absolved from foods –, which causes the neurons to stop producing NPY and start making another neurotransmitter called PONC, which gives the sensation of satiety.
The balance and fluctuation of the two neurotransmitters is the physiological control mechanism that causes human beings to have cycles of hunger and satiety.
“If the neuron does not work well – like when the hypothalamus is inflamed as a result of ingesting excess saturated fat –, the cell is unable to adequately regulate the production of neurotransmitters and it cannot work properly,” Velloso explained.
Drug development
The discovery that the excess consumption of saturated fat affects proper functioning of the region of the human brain that controls hunger opens the door to the possibility for finding targets for more efficient medicines to treat obesity.
Velloso says that this is because there are few medicines available on the market to fight weight gain, and none of them act in this region of the brain.
“Today there is no good medicine for obesity, but at least we are beginning to understand where and how a new drug could work, which makes the work of developing compounds with this type of function a little easier,” he states.
Amphetamines, for example, which in recent years have been banned in many countries, including Brazil, belong to the same group of drugs as cocaine, which acts on the central nervous system and causes chemical dependency. Besides this, the side effects of amphetamines are the same as those caused by cocaine, such as an increase in heart rhythm and blood pressure.
“An ideal obesity drug should work specifically on the neurons of the hypothalamus, reducing the inflammation and improving its function, without the side effects of amphetamines,” Velloso opined.
With the discovery that the inflammation in the hypothalamus caused by excess consumption of saturated fat is one of the main causes of obesity, the team from Unicamp has worked to better understand the biological part of the inflammation, because not every inflammation is the same. “Each type of inflammation and the tissue in which it occurs present unique characteristics,” said Velloso.
Through a Thematic Projectsupported by FAPESP, the researchers plan to characterize this type of inflammation, better understand how it occurs and find a way to solve it nutritionally.
“We know that just as there are saturated fats that cause inflammation in the hypothalamus, there are also unsaturated fats, like the omegas, that can partially reverse this inflammation,” Velloso explained.
“Perhaps food substitutes can be found that can be enriched through diet and reverse this inflammation, at least in part,” concluded Velloso.