Abstract: Objective: The effects of Alternate-day modified fasting combined exercise on fat mass, muscle mass, and serum Irisin, FNDC5 and UCP1 proteins were investigated in rats with 4 weeks of aerobic exercise and modified alternate-day fasting intervention. Methods: Thirty-two healthy 8-week-old SPF male SD rats were randomly divided into control group, exercise group, alternate-day modified fasting and alternate-day modified fasting combined with exercise group, 8 rats in each group. The exercise group performed treadmill exercise with moderate exercise intensity(60 min/d,5 d/w), the alternate-day modified fasting group alternated between fasting and free feeding every other day, and fed 25% basal energy feed on fasting days, and the alternate-day modified fasting combined exercise group received two combined interventions. After 4 weeks of intervention, the body fat rate of rats was measured by apical blood sampling and abdominal aortic blood sampling, and the serum was preserved and centrifuged, and the wet weights of bilateral gastrocnemius, bilateral perirenal fat and brown fat at the scapula were weighed, and samples were collected for paraffin sectioning and HE staining, and the cell areas were counted; serum Irisin levels were measured by ELISA, and FNDC5 protein expression in gastrocnemius and UCP1 protein expression in adipose tissue were detected by Western blot. Results: After 4 weeks of intervention, compared with the Con group, energy intake, body weight and body fat were decreased significantly in the Exer, ADMF and ADMF-Exer groups (P＜0.05), the wet weight/body weight and adipocyte area of white fat were reduced significantly (P＜0.01), and there was no significant difference in scapular fat wet weight/body weight (P＞0.05). Compared with the Con group, the gastrocnemius wet weight/body weight in the ADMF group was reduced significantly (P＜0.05), while that in the ADMF-Exer group was increased significantly (P＜0.05), the muscle cross-sectional areas in the Exer group and the ADMF-Exer group were increased (P＜0.05), and the content of gastrocnemius FNDC5 protein, serum Irisin level and expression of adipose UCP1 protein in the ADMF-Exer group were increased significantly (P＜0.05). After 4 weeks of intervention, energy intake was reduced significantly in both ADMF and ADMF-Exer groups (P＜0.01) and body weight of ADMF-Exer group was decreased (P＜0.05) compared with the Exer group. Compared with the Exer group, there were no significant differences in body fat content, white fat wet weight/body weight and scapular fat wet weight/body weight between ADMF group and ADMF-Exer group (P＞0.05), and adipocyte area in ADMF-Exer group was reduced significantly (P＜0.05). Compared with the Exer group, the gastrocnemius muscle wet weight/body weight was reduced significantly in the ADMF group (P＜0.05), and the expression of FNDC5 protein, serum Irisin and adipose UCP1 protein in the ADMF-Exer group were increased significantly compared with the Exer group (P＜0.05). Conclusion: Alternate-day modified fasting combined with exercise intervention can effectively control body weight and reduce body fat in rats, and the mechanism may be through the FNDC5/Irisin-UCP1 pathway to induce browning of white adipose tissue and increase thermogenesis of brown fat.

Key words: alternate-day modified fasting, Irisin, exercise, lose fat, rats