Journal of Scientific Research and Reports

Fast-food consumption is embedded in contemporary childhood and adolescent food environments, yet the strength of evidence linking this exposure to health and developmental outcomes varies markedly by outcome and study design. This critical narrative review integrates evidence on dietary quality, adiposity, cardiometabolic risk, academic and psychosocial outcomes, environmental determinants, and policy responses. Literature published from 1 January 2000 to 30 June 2026 was identified through live searches of major open scholarly sources, supplemented by citation searching and verification of bibliographic metadata and digital object identifiers. The evidence is most consistent for immediate dietary consequences: on days when children or adolescents consume fast food, total energy intake and intakes of sugar-sweetened beverages, total and saturated fat, sodium, and added sugars tend to rise, while fruit, vegetables, milk and fibre-rich foods are displaced. Associations with adiposity are directionally plausible and supported by several longitudinal studies, but effect sizes are less consistent than for diet quality, and systematic reviews show substantial heterogeneity arising from exposure definition, residual confounding, reverse causation, and imperfect measurement of neighbourhood food access. Direct paediatric evidence for metabolic syndrome is limited but includes a prospective cohort signal. Reported associations with academic achievement, sleep disturbance and psychological distress are potentially important but remain predominantly observational; broader “junk food” or ultra-processed food evidence should not be treated as equivalent to fast-food-specific evidence. Marketing exposure, parental consumption, affordability, neighbourhood retail structure, and adolescent autonomy appear to shape consumption, often in socially patterned ways. Policy evidence indicates that information-only approaches such as calorie labelling have modest effects, whereas healthier defaults, marketing controls, price strategies and reformulation may be more promising when implementation and compliance are strong. Future research requires repeated objective exposure measurement, longer follow-up, stronger quasi-experimental designs, greater representation of low- and middle-income countries, and explicit separation of fast-food source, processing level and overall dietary pattern. Overall, frequent fast-food consumption is best regarded as a modifiable marker and contributor to poorer dietary quality, with probable but less precisely quantified downstream effects on weight and metabolic health and still-uncertain independent effects on broader development.