Fig. 1: Biochemical and physiological changes on food restriction.

a Fasting blood glucose levels in young (n = 6) and aged mice (n = 7–14) on days 5, 8, and 10 after daily food restriction (FR). Two-way ANOVA revealed a significant effect of age (#; F (1, 43) = 6.98, P = 0.0115) and age × time interaction (F (2, 43) = 3.23, P = 0.0495); **P < 0.01 vs. young FR mice at this time point by Bonferroni test. b Hypoglycemia-free survival; hypoglycemia is defined as blood glucose level <50 mg/dL; ***P < 0.001 vs. young FR mice by log-rank test. c Fasting blood β-hydroxybutyrate (βHB) levels in mice on daily FR. Two-way ANOVA revealed significant effects of age (###; F (1, 113) = 32.8, P < 0.001), time (F (5, 113) = 30.6, P < 0.001), and the age × time interaction (F (5, 113) = 5.87, P < 0.001); ***P < 0.001 aged FR mice (n = 12–13) vs. young FR mice (n = 8) at each time point by Bonferroni test. d Body temperature before feeding. Two-way ANOVA revealed significant effects of time (F (10, 206) = 10, P < 0.001) and age × time interaction (F (10, 206) = 2.8, P = 0.0029). **P < 0.01 aged FR mice (n = 8–20) vs. young FR mice (n = 6) at this time point by Bonferroni test. e Daily spontaneous activity. Two-way ANOVA revealed significant effects of age (###; F (1, 226) = 112, P < 0.001), time (F (11, 226) = 23.1, P < 0.001), and the age × time interaction (F (11, 226) = 3.17, P < 0.001), **P < 0.01, ***P < 0.001 aged FR mice (n = 7–13) vs. young FR mice (n = 10) at each time point by Bonferroni test. Data are presented as mean ± SEM (a, c, d, and e).