Early postnatal overnutrition impairs VO2max gains with moderate exercise and increase post-exercise muscle damage in adult male rats

Exercise counteracts obesity effects, but information on how early-life obesity may affect long-term adaptation to exercise is lacking. This study investigates the impact of early-life postnatal overfeeding (PO) on animals' adaptation to exercise. Only male Wistar rats were used. On postnatal day (PN) 30, rats from control (NL-9 pups) or PO (SL-3 pups) litters were separated into four groups: NL-sedentary (NL-Se), NL-exercised (NL-Ex), SL-sedentary (SL-Se), and SL-exercised (SL-Ex). Exercised groups performed moderate-intensity exercise, running on a treadmill, from PN30 to PN90. Further experiments were carried out between PN90 and PN92. PO promoted obesity in SL versus NL rats (P < 0.05). Exercise reduced body weight (P < 0.001), body fat (P < 0.01), and improved glucose homeostasis in SL-Ex versus SL-Se. SL-Ex presented lower VO2max (P < 0.01) and higher post-exercise LDH (P < 0.05) compared to NL-Ex rats. Although moderate exercise counteracted obesity in SL rats, early-life overnutrition restricts fitness gains in adulthood, indicating that early obesity may impair animals' adaptation to exercise.