Stress and Cortisol: How They Affect Your Results

The word cortisol has a bad reputation in the fitness world — people equate it with stress, fat storage, and muscle loss. The reality is quite different: cortisol is essential for energy, alertness, and immune function. Problems only arise when the rhythm is disrupted.

Cortisol isn't a stress hormone — it's an energy hormone

Cortisol is not merely a "stress hormone," as it's often oversimplified. Its primary role is mobilizing glucose and energy to tissues that need it. Cortisol follows a 24-hour rhythm: high in the morning, gradually declining throughout the day, lowest at night. When this rhythm is correct, you have energy in the morning, focus during the day, and quality sleep at night.

Chronic stress, cortisol, and body composition

When stress is chronically elevated, cortisol doesn't return to baseline. The consequences are well documented: increased visceral fat storage, muscle tissue breakdown, and sleep disturbances. A review in International Journal of Molecular Sciences (Andreadi et al., 2025) confirmed that disrupted cortisol rhythms contribute to metabolic disorders, cardiovascular disease, and impaired cognitive function.

5 evidence-based tools for regulating cortisol

1. Morning sunlight. One of the most important free habits for health. Research in International Journal of Molecular Sciences (Andreadi et al., 2025) confirmed that light exposure after waking strengthens the morning cortisol peak. 5–10 minutes outside on a sunny day, 15–20 on a cloudy one.

2. Delayed caffeine. Caffeine raises cortisol. If you consume it right after waking, you "steal" the natural peak and create an afternoon crash. Delay your coffee 60–90 minutes after waking.

3. Physiological sigh. Double inhale through the nose, long exhale through the mouth. A Stanford study (Balban et al., 2023, Cell Reports Medicine) showed this lowers heart rate and activates the parasympathetic system in 1–3 breaths — more effectively than meditation.

4. NSDR / Yoga Nidra. 10–30 minutes of guided relaxation proven to lower cortisol. A study in Stress and Health (Cooke et al., 2024) confirmed that online yoga nidra reduces daytime cortisol and improves well-being.

5. Complex carbohydrates in the evening. Some studies suggest that complex carbohydrates (whole grains, sweet potatoes, legumes) in the evening may ease the transition to sleep — via insulin-facilitated tryptophan uptake, a precursor to melatonin (Afaghi et al., 2007, Am J Clin Nutr; St-Onge et al., 2016, J Clin Sleep Med). The effect is individual and not guaranteed for everyone. Note: refined starches and sugars may have the opposite effect.

Burnout: two patterns, two approaches

One hypothesis in the literature proposes that the cortisol pattern changes with the duration of chronic stress (Miller et al., 2007, Psychol Bull; Jonsdottir & Sjörs Dahlman, 2019). Early phase: elevated HPA axis activity — too much stress in the morning, exhaustion in the afternoon. Late phase: reduced HPA axis activity — fatigue in the morning, tension at night ("tired but wired"). Important: this model is a hypothesis, not established fact — research shows heterogeneous results and there is no single biomarker for burnout (Danhof-Pont et al., 2011, Scand J Work Environ Health).

Approaches commonly used in practice for the early phase: NSDR (non-sleep deep rest), delayed caffeine, reducing morning stimulation, and shorter, less intense workouts. For the late phase: breathing exercises (Ma et al., 2017, Front Psychol), dimming lights before bed, complex carbohydrates in the evening, limiting screens, and reducing evening stimulation. There is no universal fix — the approach is always individual and depends on the full picture.

References

• Andreadi, A. et al. (2025). Modified Cortisol Circadian Rhythm. International Journal of Molecular Sciences, 26(5), 2090.
• Balban, M.Y. et al. (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine, 4(1), 100895.
• Cooke, S. et al. (2024). Online Yoga Nidra and Diurnal Salivary Cortisol. Stress and Health, 40(1).
• Epel, E.S. et al. (2023). Stress, telomeres, and psychopathology: toward a deeper understanding of a triad of early aging. Annual Review of Clinical Psychology, 19, 441–462.
• Huberman, A. (2024). Tools for managing stress in real time. Huberman Lab Podcast.
• Huberman, A. (2025). Cortisol and burnout protocols. Huberman Lab Podcast.
• Keller, A. et al. (2012). Does the perception that stress affects health matter? The association with health and mortality. Health Psychology, 31(5), 677–684.
• Laukkanen, J.A. et al. (2023). The interplay between systolic blood pressure, sauna bathing, and cardiovascular mortality. Journal of Nutrition, Health and Aging, 27(5), 348–353.
• Liu, P.Y. (2024). Rhythms in cortisol mediate sleep and circadian impacts on health. SLEEP, 47(9), zsae151.