Energy balance in cyclists on plant-based diets during a 30-day, 4300-km ride across Canada: Two case studies.

The popularity of ultra-endurance events and plant-based diets highlights the importance of understanding the energetics of athletes with diverse dietary preferences. This study examined energy balance in two recreational cyclists on plant-based diets (male, 41 years; female, 38 years) during a 30-day cross-Canada ride. Resting energy expenditure was measured via whole-room indirect calorimetry before and after the ride. Total energy expenditure (TEE) was assessed using doubly labeled water during the first and last weeks of the ride and used to calculate physical activity energy expenditure (PAEE) and physical activity level (PAL). Body composition was assessed with deuterium dilution, and dietary intake was recorded using food scales, written records, and photographs. Cyclists averaged 154.8 ± 24.0 km/day early and 118.2 ± 25.3 km/day late in the ride. Body weight showed minimal variation, but the male's fat mass decreased by 2.3 kg and fat-free mass increased by 1.4 kg. Both cyclists increased energy intake (female: +421 kcal/day; male: +761 kcal/day), with protein intake >2.3 g/kg/day. TEE increased in the female (+683 kcal/day) but remained relatively stable in the male (-137 kcal/day), driven by PAEE. PAL remained high (female: 3.71-4.11; male: 3.76-3.94). These findings highlight the high energy demands of ultra-endurance cycling and the need for tailored strategies, particularly for athletes on plant-based diets.