Background& purpose: Obesity and thyroid disorders can disrupt hormonal and metabolic circadian rhythms, and implementing combined exercise and nutritional interventions may play an important role in restoring these rhythms. The present study aimed to investigate the effects of eight weeks of high-intensity functional training combined with time-restricted fasting on circadian rhythm–related hormones in obese women with and without hypothyroidism. Methods: Forty-eight inactive obese women were assigned to four groups: (1) high-intensity functional training combined with time-restricted fasting in obese women without thyroid disorders, (2) time-restricted fasting alone, (3) control group, and (4) high-intensity functional training combined with time-restricted fasting in obese women with hypothyroidism. The time-restricted fasting protocol followed a 16:8 schedule, and high-intensity functional training was performed three times per week for eight weeks. Serum hormone concentrations were measured in a fasting state before and after the intervention. Two-way repeated measures ANOVA with Tukey post-hoc tests was used to analyze the data. Results: The findings showed that serum leptin and cortisol levels decreased significantly in all three intervention groups—functional training plus fasting (healthy), functional training plus fasting (hypothyroid), and fasting alone—compared with the control group (p≤0.05). Additionally, a significant reduction in TSH was observed only in the groups that performed high-intensity functional training in combination with fasting. In contrast, testosterone and GH levels did not show significant changes following the intervention (p≤0.05).. Conclusion: Based on the results, the combination of high-intensity functional training and time-restricted fasting was more effective than fasting alone and partially restored disrupted hormonal rhythms in obese women, both with normal thyroid function and with hypothyroidism. Therefore, this combined approach appears to be a promising strategy for improving metabolic status and circadian rhythm regulation in this population.
Al-Dakheel, A. J. J. and Khodaei, K. (2026). The Effect of High-Intensity Functional Training Combined with Time-Restricted Fasting on Serum Circadian Rhythm Hormones in Obese Women with and Without Hypothyroidism. Journal of Applied Health Studies in Sport Physiology, (), -. doi: 10.22049/jahssp.2026.31299.1801
MLA
Al-Dakheel, A. J. J. , and Khodaei, K. . "The Effect of High-Intensity Functional Training Combined with Time-Restricted Fasting on Serum Circadian Rhythm Hormones in Obese Women with and Without Hypothyroidism", Journal of Applied Health Studies in Sport Physiology, , , 2026, -. doi: 10.22049/jahssp.2026.31299.1801
HARVARD
Al-Dakheel, A. J. J., Khodaei, K. (2026). 'The Effect of High-Intensity Functional Training Combined with Time-Restricted Fasting on Serum Circadian Rhythm Hormones in Obese Women with and Without Hypothyroidism', Journal of Applied Health Studies in Sport Physiology, (), pp. -. doi: 10.22049/jahssp.2026.31299.1801
CHICAGO
A. J. J. Al-Dakheel and K. Khodaei, "The Effect of High-Intensity Functional Training Combined with Time-Restricted Fasting on Serum Circadian Rhythm Hormones in Obese Women with and Without Hypothyroidism," Journal of Applied Health Studies in Sport Physiology, (2026): -, doi: 10.22049/jahssp.2026.31299.1801
VANCOUVER
Al-Dakheel, A. J. J., Khodaei, K. The Effect of High-Intensity Functional Training Combined with Time-Restricted Fasting on Serum Circadian Rhythm Hormones in Obese Women with and Without Hypothyroidism. Journal of Applied Health Studies in Sport Physiology, 2026; (): -. doi: 10.22049/jahssp.2026.31299.1801
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