Unhealthy and Unequal: Socioeconomic Vulnerability Shapes Dietary Quality in Children and Adolescents from Spain

<b>Background/Objectives</b>: Childhood obesity and nutritional inequalities remain major public health challenges, particularly in socioeconomically disadvantaged settings. In Spain, these disparities are reflected in unequal access to healthy food and differing health outcomes among the young population. This study aimed to explore how social vulnerability influences dietary patterns, body composition, and food insecurity among children and adolescents, with a particular focus on sex differences. <b>Methods</b>: A descriptive cross-sectional study was conducted with 280 participants aged 6 to 15 years old, recruited from urban areas across Spain. Two groups were evaluated, a socioeconomically vulnerable group (VG) (<i>n</i> = 175) and a non-vulnerable group (NVG) (<i>n</i> = 105), classified according to socioeconomic and social established criteria. Validated tools were used to assess diet quality, adherence to the Mediterranean Diet (MD), consumption of ultra-processed foods (UPF), and household food insecurity. Anthropometric measurements were also collected, and body mass index (BMI) was calculated using both national and international reference standards. <b>Results</b>: Vulnerable children and adolescents showed higher prevalence of food insecurity, less favorable body composition indicators, and lower global dietary quality, characterized by lower adherence to the MD and higher consumption of UPF. Multivariate analysis confirmed that socioeconomic vulnerability was significantly associated with female sex, higher BMI, lower adherence to the MD, and greater consumption of UPF. <b>Conclusions</b>: Our findings highlight a concerning pattern of health and nutritional inequality among children and adolescents based on socioeconomic status. There is a clear and urgent need for effective public health strategies with an equity focus that promote healthy and affordable eating habits from early life, especially in the most disadvantaged environments and targeted by gender.