Men VS Women: The Biological Differences in Circadian Rhythms, Hormones, and Sports Nutrition

For years, sports nutrition and exercise science have been largely based on male physiology, but emerging research suggests that men and women have distinct biological rhythms, hormonal patterns, and metabolic needs. While the science is still evolving, understanding these differences can lead to more effective, personalised nutrition and training strategies.

Circadian Rhythms: Do Men and Women Operate on Different Clocks?

Circadian rhythms, the body’s internal clock, govern everything from sleep cycles to metabolism and hormone regulation. However, research indicates that men and women may have variations in their biological clocks:

🕒 Women’s circadian rhythm tends to be shorter than men’s, meaning they may naturally wake up and feel sleepy earlier (Roenneberg et al., 2019). This suggests that women might benefit from an earlier eating and training schedule compared to men.

🕒 Men, on average, have a slightly later chronotype, meaning they might perform better in the evening for both cognitive and physical activities (Adan et al., 2012).

Hormonal Variability: The Impact on Nutrition and Training

Hormonal differences significantly influence energy metabolism, recovery, and muscle adaptation.

1. The Menstrual Cycle & Metabolism

Women’s hormonal fluctuations across the menstrual cycle affect their energy utilisation, appetite, and exercise recovery:

• Follicular Phase (Days 1-14): Oestrogen levels rise, which may enhance fat oxidation, making the body more efficient at using fat as fuel during endurance exercise (Campbell et al., 2021).

• Luteal Phase (Days 15-28): Increased progesterone raises core body temperature, leading to higher carbohydrate oxidation and potential shifts in appetite regulation (Elliott-Sale et al., 2022). Women may feel stronger in resistance training but experience reduced endurance performance during this phase.

2. Testosterone & Muscle Growth in Men

Men have significantly higher testosterone levels, which enhances muscle protein synthesis, recovery, and strength gains (Kraemer et al., 1998). This allows men to build muscle more efficiently than women, even when training volume is similar.

3. Cortisol & Stress Response

Women tend to have a heightened cortisol response to stress compared to men, which may impact recovery and muscle retention, particularly under high training loads or inadequate nutrition (Tomas et al., 2019). Prioritising adequate rest and recovery nutrition is essential for female athletes.

Timing of Nutrition: Does It Matter?

Nutrient timing is an area where sex differences are underexplored. However, early findings suggest:

✔ Women may benefit from eating earlier in the day, as they have a more pronounced insulin sensitivity in the morning, making breakfast and lunch optimal for carbohydrate intake (Manoogian et al., 2019).

✔ Men may tolerate later meals better, as they exhibit less variation in insulin sensitivity across the day, potentially allowing for effective late-evening meals or workouts without as much metabolic impact.

Sports Nutrition & Supplementation: What’s Different?

Protein Needs & Utilisation

• Women may require more protein relative to body weight to maximise muscle protein synthesis due to lower testosterone levels (Moore et al., 2020).

• Men typically retain muscle mass more efficiently, allowing for slightly lower protein intake relative to muscle mass gains.

Carbohydrate Needs

• During high-intensity training, women oxidise more fat and fewer carbohydrates than men (Tarnopolsky, 2008). Therefore, men may require higher carbohydrate intake to fuel anaerobic performance.

• Women may experience fluctuations in carbohydrate metabolism across the menstrual cycle, needing higher intake in the luteal phase for optimal glycogen replenishment.

Creatine Supplementation

• Women may benefit more from lower doses of creatine (3g/day) due to naturally higher intramuscular creatine levels, while men often require 5g/day or more (Smith-Ryan et al., 2021).

Why is the Research Still Limited?

Historically, most sports science research has been conducted on male subjects, with female participants making up less than 40% of studies in exercise physiology (Costello et al., 2014). This has left gaps in knowledge, particularly regarding hormonal influences on metabolism, strength training adaptations, and recovery.

Additionally, menstrual cycle phases and hormone fluctuations add complexity, making female-based research more variable and harder to standardise. However, with growing interest in personalised nutrition and gender-specific training protocols, more research is emerging to bridge this gap.

Final Thoughts: The Future of Gender-Specific Nutrition

While men and women share fundamental nutrition and training principles, the differences in circadian rhythm, hormones, and metabolism suggest that a more individualised approach could lead to better performance, recovery, and health outcomes.

As science evolves, we will likely see more tailored nutrition and exercise strategies designed to optimise results for both men and women based on their unique physiological differences. Until then, listening to your body, tracking personal responses to nutrition and training, and applying evidence-based insights remain the best strategies for both men and women.

References

1. Roenneberg, T., Allebrandt, K. V., Merrow, M., & Vetter, C. (2019). Human circadian clocks: The importance of sex differences. Journal of Biological Rhythms, 34(6), 579-584.

2. Adan, A., Archer, S. N., Hidalgo, M. P., Di Milia, L., Natale, V., & Randler, C. (2012). Circadian typology: A comprehensive review. Chronobiology International, 29(9), 1153-1175.

3. Campbell, B. I., Batrakoulis, A., & King, S. (2021). Female-specific training and nutrition considerations across the lifespan. Sports Medicine, 51(4), 687-709.

4. Elliott-Sale, K. J., Minahan, C. L., de Jonge, X. A., Ackerman, K. E., & Sipilä, S. (2022). Exercise and the female reproductive system. The Lancet, 399(10343), 2207-2216.

5. Kraemer, W. J., Häkkinen, K., Triplett-McBride, T., & Fry, A. C. (1998). Physiological changes with resistance training in older and younger men and women. Journal of Applied Physiology, 85(5), 2002-2012.

6. Manoogian, E. N., Panda, S., & Chaix, A. (2019). Time-restricted eating for the prevention and management of metabolic diseases. Endocrine Reviews, 40(2), 325-338.

7. Moore, D. R., Churchward-Venne, T. A., Witard, O. C., Breen, L., Burd, N. A., Tipton, K. D., & Phillips, S. M. (2020). Protein ingestion to stimulate myofibrillar protein synthesis. Sports Medicine, 50(1), 85-97.

8. Smith-Ryan, A. E., Cabre, H. E., Eckerson, J. M., & Candow, D. G. (2021). Creatine supplementation in women’s health: A lifespan perspective. Nutrients, 13(6), 1915.

9. Costello, J. T., Bieuzen, F., & Bleakley, C. M. (2014). Where are all the female participants in sports and exercise medicine research? European Journal of Sport Science, 14(8), 847-851.