By Elton Alisson | Agência FAPESP – If obesity continues to grow at the current rate in Brazil, by 2020, it will be as prevalent as in the United States or Mexico, where approximately 35% of the population are overweight.
This forecast was made at an event held by FAPESP and the São Paulo State Assembly Institute (ILP) on August 20, 2018. Scientists and researchers met at the assembly building in the state capital to discuss obesity as part of the “FAPESP-ILP Cycle”.
The prevalence of obesity in Brazil has risen since the turn of the twentieth century, largely owing to changes in eating habits. In recent decades, Brazilians have replaced staples such as rice, beans and salad with ultra-processed foods.
“The increasingly obesogenic dietary environment has influenced lifestyles and contributed to growth in the proportion of overweight adults and children,” said Patricia Constante Jaime, a professor in the Nutrition Department of the University of São Paulo’s Public Health School (FSP-USP).
According to the latest National Health Survey conducted by IBGE, the Brazilian census bureau, 20.8% of the Brazilian adult population, or 26 million people, are obese. Overweight and obesity are common in all age and income groups but more so among women than men.
To investigate the link between diet and the growing prevalence of obesity more deeply, scientists at the University of São Paulo’s Center for Epidemiological Research in Nutrition and Health (NUPENS-USP), with which Constante Jaime is affiliated, studied Brazilians’ dietary patterns in recent decades using data from IBGE’s Household Budget Survey (POF).
The POF is conducted every six to ten years. The 2017-18 edition is ongoing. The previous edition, conducted in 2008-09, showed a decline in the consumption of rice, beans, meat, milk, sugar, edible oils and fats, alongside a rising preference for bread, biscuits, and soft drinks, among other items. The researchers at NUPENS were intrigued by the fall in consumption of sugar, oil and fat, all of which are linked to the development of obesity.
“If the consumption of these nutrients has fallen and the prevalence of obesity has risen, something wasn’t making sense in the interpretation of this phenomenon,” Constante Jaime said.
The researchers then began analyzing dietary patterns in terms of food processing instead of nutrients and detected rising consumption of ultra-processed foods instead of raw or minimally processed foods.
Ultra-processed food products, as defined by NUPENS, are industrial formulations made of substances extracted or synthesized from real foods, such as textured vegetable protein (TVP), and blended with chemical additives designed to enhance their attractiveness, smell and flavor. Studies performed with FAPESP’s support show that ultra-processed food products account for 20% of the average Brazilian’s total calorie intake.
“Ultra-processed food products aren’t industrialized foods but industrial formulations,” Constante Jaime said. “They undergo a series of processes that make it impossible to identify the original food matrix, and they contribute to rising consumption of sugar and saturated and trans fats.”
She added that ultra-processed food products are “hyperpalatable” (irresistibly appealing), promote the consumption of sugar and other addictive ingredients, and alter the natural process of satiety control. “Studies have shown that these industrial formulations cause alterations in the neurological mechanisms relating to satiety,” she said.
Fat, neurons and melatonin
At the University of Campinas (UNICAMP), scientists affiliated with the Obesity and Comorbidities Research Center (OCRC), a Research, Innovation and Dissemination Center (RIDC) supported by FAPESP, have found that a diet containing high levels of saturated fat can damage the neuronal circuits relating to satiety.
In experiments with mice, they showed that saturated fats such as stearic acid caused the death of pro-opiomelanocortin (POMC) neurons in the hypothalamus, a part of the brain that plays a vital role in controlling many bodily functions, including the release of hormones.
POMC neurons play an important role in the regulation of appetite, acting as nutrient sensors and telling the organism when it is time to stop eating because energy is available for expenditure. Individuals who lack these sensors crave fatty and/or sweet food, but their metabolism becomes sluggish, and they tend to become obese because they store a large proportion of their energy intake from an unbalanced diet.
“We have evidence that other nutrients can bring about a recovery of these neurons that control energy expenditure,” said OCRC chair Licio Augusto Velloso during the event (read more at agencia.fapesp.br/26189).
Other factors besides eating habits can contribute to obesity, such as sleep disorders, disturbed biological rhythms and abnormal production of melatonin, noted José Cipolla Neto, Full Professor in the University of São Paulo’s Biomedical Science Institute (ICB-USP).
These three factors are responsible for regulating the body’s energy balance and weight. They also modulate insulin secretion and the production of other important hormones.
According to Cipolla Neto, sleeping during the day instead of at night, getting too little sleep and producing insufficient melatonin because of artificial lighting after dark can cause a breakdown in the rhythmic distribution of these biological functions (chronodisruption), triggering the development of obesity.
“A regular daily rhythm in which wakefulness during the day alternates with nighttime sleep and rest, so that melatonin is produced in adequate amounts, ensures a proper energy balance and body weight control,” he said.
Genetic factors can also contribute to obesity, according to Carla Barbosa Nonino, who chairs the Nutrigenomics Laboratory at the University of São Paulo’s Ribeirão Preto Medical School (FMRP-USP).
Nonino said more than 100 genes are known to be associated with energy expenditure, appetite, satiety, adipose tissue formation, and lipid and insulin metabolism, among other factors.
“We set out to analyze the interaction between nutrition and the genome in patients with obesity,” Nonino explained. “This scientific field, known as nutrigenomics, is relatively new, and more obesity-associated genes are discovered every day.”
In a study supported by FAPESP, Nonino and collaborators analyzed patients with different genetic profiles and specific polymorphisms in obesity-linked genes. The results indicated that genetics can significantly influence body mass index and the amount of body fat.
“Genetics isn’t the determining factor for the development of obesity, but it’s a trigger,” Nonino said.