The final body masses of chicks were not different between groups. The mass-specific resting metabolic rate of re-fed king penguin chicks (2.7±0.1 W kg−1) was 17% higher than that of fasted chicks (2.3±0.2 W kg−1). Chicks lost an average of 1.10±0.08 kg (13±1% of initial body mass) over the 10 days of fasting (Fig. 1). In the last 3 days of fasting, the daily loss in mass expressed per chick or per unit of body mass was 72±6 g and 9.1±0.6 g kg−1, respectively. From these data, we can calculate that the mean energy equivalent of body mass loss was 21.2 kJ g−1. All these values indicate that winter-acclimatized fasted chicks were in phase II of fasting at the time of experiment, a long phase of energy economy that is characterized by low energy expenditure and high lipid catabolism (Barré, 1984; Cherel and Le Maho, 1985; Cherel et al., 1993b; Robin et al., 1988; Groscolas, 1990).