Purpose <p>Low-carbohydrate time-restricted eating (LCTR) and sprint interval training (SIT) independently improve cardiometabolic health, but their combined effects on cardiac-specific biomarkers remain unknown. We investigated whether LCTR, with or without SIT, affects N-terminal pro-brain natriuretic peptide (NT-proBNP) and cardiac troponin T (cTnT) concentrations in young adults.</p> Methods <p>Sixty-one young adults (31 males, 30 females) were randomized to a 4-week program of LCTR alone or LCTR + SIT. All participants consumed ≤ 10% of energy from carbohydrates within an 8-hour daily window. LCTR + SIT groups additionally performed 5 weekly sessions of 10 × 6-second sprints with 9-second recovery periods. Body composition, V̇O₂_max, and NT-proBNP and cTnT were assessed pre- and post-intervention. Data were analyzed using three-way mixed ANOVA with intervention (LCTR vs. LCTR + SIT) and sex as between-subjects factors, and time as within-subjects factor.</p> Results <p>Body fat decreased across all groups (range -1.2 to -2.6&#xa0;kg, <i>P</i> &lt; 0.05), with no significant between-group differences. Significant intervention × time interaction was observed for V̇O₂_max (<i>P</i> = 0.003), whereas NT-proBNP showed a significant intervention × sex × time interaction (<i>P</i> = 0.016). Post-hoc analyses revealed that only females in the LCTR + SIT group demonstrated a significant improvement in V̇O_2max (+ 17.1%, <i>P</i> = 0.014) and a reduction in NT-proBNP (-48%, <i>P</i> = 0.0005). Resting cTnT levels did not change in any group, with most values at or below detection limits.</p> Conclusion <p>Brief LCTR, with or without SIT, reduced body fat in both sexes. Only females in the LCTR + SIT group demonstrated reduced resting NT-proBNP. Reasons for, and implications of, this rapid and sex-mediated adaptation in NT-proBNP are worthy of further study.</p>