Short-Term, Significant Gains from a 10-Day Field-Based Multi-Modal Outdoor Activity Camp with Time-Restricted Feeding Dissipate at Three-Month Follow-Up.

Objectives: This single-arm, pre-post intervention study with a three-month follow-up aimed to determine whether a ten-day outdoor camp combining mixed-modality physical activity and time-restricted feeding elicits positive changes in multiple body-composition outcome measures and whether those changes persist at three-month follow-up. Methods: Forty healthy undergraduates (18 male, 22 female) participated in a 10-day outdoor camp that combined multi-modal physical activities (rock climbing and bouldering, swimming, hiking, applied paddling, survival skills, etc.) with a 13 h daily time-restricted feeding window. Body fat percentage, skeletal muscle percentage, body mass, total body-water percentage, visceral fat level, and skeletal muscle index were measured using the InBody 270 at baseline, immediately post-camp, and at the three-month follow-up. Results: Mixed-effects models with random intercepts for subject revealed significant reductions in body fat percentage (β = -1.63, p < 0.001) and visceral fat level (β = -0.72, p = 0.001), alongside increases in skeletal muscle percentage (β = 1.02, p < 0.001), skeletal muscle index (β = 0.30, p < 0.001), and total body-water percentage (β = 1.19, p < 0.001) from baseline to post-camp; no outcomes differed between baseline and follow-up and no time × sex interactions were observed. Conclusions: These findings indicate that a brief, intensive nature-based intervention can drive rapid, multidimensional improvements in body composition, but structured maintenance is required to sustain benefits.