The alarming prevalence of obesity in children and adolescents reflects the nutritional transition occurring in the population, which involves both dietary patterns and the family environment. Dietary patterns among the pediatric population have changed over time, with increased consumption of energy-dense foods that are low in fiber and micronutrients but rich in fat and refined sugar.^(1,2) These foods are generally highly processed and were developed to produce ready-to-eat, durable, convenient, and profitable products. Recent studies increasingly highlight the association between greater consumption of highly processed foods and the development of obesity.^(1–3)

An important category of ultra-processed foods (UPFs) is sugar-sweetened beverages (SSBs), which may contribute substantially to the epidemic of overweight and obesity in children and adolescents because of their high added sugar content, low satiety, and poor nutritional contribution to total energy intake.^(4,5) As body fat increases, the inflammatory profile and hormonal regulation of hunger and metabolism change. In this context, the expression and secretion of leptin and adiponectin change and are modulated by body mass index, adipocyte size, distribution, and function, as well as by sex, dietary components, and inflammatory cytokines.^(6,7)

Leptin plays an important role in regulating energy balance, food intake, and body weight. Patients with obesity often develop leptin resistance, which impairs the neuroendocrine regulation of energy homeostasis.^(7–9) Furthermore, hyperleptinemia has been associated with pro-inflammatory conditions in adolescents with obesity. Adiponectin, in contrast, is secreted by adipocytes and plays a beneficial role in glucose and lipid metabolism by reducing the inflammatory state. This adipocytokine suppresses hepatic glucose production and improves insulin sensitivity.⁽¹⁰⁾ However, adiponectin levels decrease in adolescents with obesity, occurring in parallel with hyperleptinemia. These findings suggest that both hormones act as key mediators of obesity-related inflammatory processes in this population. In fact, the leptin/adiponectin ratio is directly associated with glucose metabolism and adipose tissue function and has been proposed as a potential biomarker of inflammation.^{(11, 12)}

Studying the relationship between the pathophysiological aspects of these conditions and dietary intake remains important, because dietary patterns can trigger and amplify inflammation-related factors that worsen obesity and contribute to the development of comorbidities. Few studies have examined the relationship between these hormones and the consumption of SSBs, particularly in pediatric populations. In addition, limited evidence has evaluated the combined impact of SSB and UPF consumption on inflammatory biomarkers in Brazilian adolescents. We hypothesized that a higher intake of SSBs and UPFs would be associated with elevated inflammatory markers, including an increased leptin/adiponectin ratio.

This study evaluate the impact of sugar-sweetened beverages and ultra-processed foods intake on the leptin/adiponectin ratio, an important biomarker of inflammation, in adolescents with obesity.

This cross-sectional observational study included post-pubertal adolescents recruited from clinical and community settings, including outpatient clinics and local schools, to ensure a representative sample and improve reproducibility. Seventy post-pubertal adolescents with obesity aged 15-19 years of both sexes participated in the study. The inclusion criteria were Tanner stage V,⁽¹³⁾ primary obesity, and body mass index greater than the 95th percentile according to the World Health Organization reference growth charts. The exclusion criteria included use of oral contraceptives, corticosteroids, or anti-epileptic drugs, history of renal disease, alcohol consumption, smoking, and secondary obesity resulting from endocrine disorders. The study followed the principles of the Declaration of Helsinki and received approval from the research ethics committee of the Universidade Federal de São Paulo (CAAE: 45564721.4.0000.5505; # 4.846.311). All procedures were explained to the guardians of the participants, and written informed consent was obtained.

Participants underwent an initial assessment to collect sociodemographic and health information provided by the adolescents or their guardians. This assessment included questions on birth history, weight, duration of breastfeeding, race, history of childhood respiratory diseases, rhinitis, or sinusitis, family history of smoking, asthma and obesity, socioeconomic status, and pubertal stage. A complete clinical evaluation, blood tests, and blood pressure measurements were performed by an endocrinologist. On the scheduled assessment day, blood samples were collected, and anthropometric and body composition measurements were obtained. A 24-hour dietary recall was also administered to assess food intake.

Table 1 presents the analysis of body composition, circumferences, leptin, adiponectin, and leptin/adiponectin ratio values. Adolescents who consumed SSBs exhibited significantly higher fat-free mass (kg), body weight, resting metabolic rate, and pro-inflammatory leptin/adiponectin ratio than non-intakers, highlighting the potential metabolic and inflammatory impact of SSB consumption.

Table 2 presents food intake according to the level of food processing for SSB intakers and non-intakers. Adolescents who consumed SSBs had significantly higher intake of grams, energy (kcal), proteins, lipids, cholesterol, carbohydrates, fiber, and both saturated and polyunsaturated fats from ultra-processed foods. They also showed higher cholesterol intake from processed foods than non-intakers. These differences were statistically significant and clinically relevant, particularly for energy intake and the leptin/adiponectin ratio.

Finally, positive and statistically significant associations were observed between UPF intake and body weight, waist circumference, and neck circumference, highlighting the role of UPFs in influencing anthropometric and inflammatory markers in adolescents with obesity (Table 3).

This study focused on food quality and tested the hypothesis that UPF intake and SSB consumption are associated with alterations in variables involved in the pathophysiology of obesity in adolescents. The results showed that higher consumption of SSBs and UPFs was associated with an increased pro-inflammatory biomarker, the leptin/adiponectin ratio, as well as with higher body mass and greater waist and neck circumferences. These findings support the role of diet in modulating inflammatory status in adolescents with obesity (Figure 1).

Routine intake of UPFs and saturated fats plays a key role in the development of obesity by promoting hypothalamic inflammation and reducing hypothalamic responsiveness to satiety signals.^(11,18,19) Recent evidence suggests that UPF consumption can directly disrupt neural circuits involved in appetite regulation, independently of adiposity, thereby contributing to overconsumption and weight gain.⁽²⁰⁾ To our knowledge, this study represents the first investigation in Brazil, and among the first in Latin America, to evaluate the relationship between high UPF and SSB intake and inflammatory biomarkers such as the leptin/adiponectin ratio in adolescents with obesity.

Food intake and obesity are influenced not only by caloric content but also by the degree of food processing.^(21–23) In addition to their low nutritional value, UPFs may stimulate appetite because of their high glycemic load, whereas minimally processed foods promote greater satiety.^(24–26) Sugar-sweetened beverages as liquid UPFs, generate weaker satiety signals than solid foods.⁽²⁷⁾

Adipokines play a central role in the pathophysiology of obesity because of variations associated with nutritional status.^(12,28) Leptin stimulates anorexigenic pathways and regulates inflammatory processes. However, in obesity, leptin resistance develops, leading to hyperleptinemia and promoting a pro-inflammatory state, insulin resistance, and elevated blood pressure.^(12,29,30) In contrast, adiponectin, which improves insulin sensitivity and metabolic regulation, decreases in adolescents with obesity. This imbalance results in a state of hyperleptinemia with concomitant hypoadiponectinemia and reduced satiety signaling.

The leptin/adiponectin ratio reflects this pathophysiological context and provides a more integrated marker than isolated leptin or adiponectin measurements, showing associations with body mass index, weight, glycemic markers, insulin resistance, and other cardiometabolic comorbidities.^{(12,28,30–32)}

In the present sample, UPF intake represented 39% of total energy intake among non-consumers of SSBs and 69% among SSB consumers, indicating a 30% higher intake in adolescents who consumed SSBs. This difference may help explain the observed metabolic differences between groups. These findings align with other Brazilian studies reporting associations between UPF consumption and overweight or abdominal obesity.^(3,33,34)

Sugar-sweetened beverages remain the primary source of added sugars in adolescent diets. Fructose from SSBs promotes hepatic lipogenesis, fat accumulation, insulin resistance, and the release of pro-inflammatory cytokines, thereby increasing the risk of type 2 diabetes and cardiovascular disease.⁽³⁵⁾ The present findings reinforce the need for public health strategies to reduce UPF and SSB consumption among adolescents, including school-based nutritional interventions and broader policy initiatives aimed at promoting healthier dietary patterns and preventing obesity and related metabolic disorders.

Although the sample consisted exclusively of adolescents with obesity, differences in SSB consumption were associated with higher UPF intake, greater total energy intake, and higher cholesterol consumption. The fiber-to-carbohydrate ratio was lower among SSB consumers, reflecting a less balanced dietary pattern that may exacerbate obesity and increase the risk of chronic disease progression.

This study has some limitations, including the use of a single 24-hour dietary recall, which may not reflect habitual intake. However, strengths include the integration of dietary and biochemical markers and the high statistical power achieved.

In summary, the present investigation suggests a relationship between sugar-sweetened beverages intake and the high consumption of ultra-processed foods among adolescents with obesity, which may contribute to differences in pro-inflammatory biomarkers, reflected by a higher leptin/adiponectin ratio in this population. All participants had a diagnosis of obesity, and these findings highlight the importance of diet quality in preventing pro-inflammatory states and comorbidities commonly associated with obesity in adolescents. These results support the development of guidelines and preventive interventions aimed at reducing sugar-sweetened beverages and ultra-processed foods consumption among adolescents.