Abstract The incidence of non-alcoholic fatty liver disease (NAFLD) tends to be younger. And the role of theobromine in fatty liver disease remains unclear. The purpose of this study was to investigate the relationship between dietary theobromine intake and degree of hepatic steatosis in individuals aged 45 and below, using data from the 2017–2020 National Health and Nutrition Examination Survey (NHANES) and liver ultrasonography transient elastography. A total of 1796 participants aged below 45 years were included from NHANES 2017–2020 data after applying exclusion criteria. Multivariate regression and subgroup analyses were conducted to examine the associations between theobromine intake and controlled attenuation parameter (CAP), adjusting for potential confounders. Generalized additive models and two-piecewise linear regression were used to analyze nonlinear relationships. In the unadjusted Model 1 and preliminarily adjusted Model 2, there was no significant correlation between theobromine intake and CAP values. However, in Models 3 and 4, which accounted for confounding factors, a higher intake of theobromine was significantly associated with lower CAP values. Subgroup analyses in the fully adjusted Model 4 revealed a significant negative correlation among individuals aged 18–45, women, and white populations. Nonlinear analysis revealed a U-shaped relationship in black Americans, with the lowest CAP values at 44.5 mg/day theobromine. This study provides evidence that higher theobromine intake is correlated with lower degree of hepatic steatosis in young people, especially those aged 18–45 years, women, and whites. For black Americans, maintaining theobromine intake around 44.5 mg/day may help minimize liver steatosis. These findings may help personalize clinical nutritional guidance, prevent the degree of hepatic steatosis, and provide pharmacological approaches to reverse fatty liver disease in young people.