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These studies suggest that intermittent fasting increases cortisol production and alters its balance with cortisone.
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Intermittent fasting (IF) has gained popularity for its potential health benefits, including weight loss and improved metabolic health. However, its effects on hormone production, particularly cortisone and cortisol, are complex and significant. Cortisol, a glucocorticoid hormone produced by the adrenal glands, plays a crucial role in stress response, metabolism, and immune function. Understanding how intermittent fasting influences cortisol and its inactive form, cortisone, is essential for comprehending the broader implications of fasting on health.
Research consistently shows that intermittent fasting leads to an increase in cortisol levels. A study involving 22 healthy volunteers demonstrated that both overfeeding and fasting increased total and free cortisol levels, as well as the free cortisol-to-cortisone ratio . This suggests that fasting not only elevates cortisol but also affects the balance between cortisol and cortisone.
The mechanisms behind the increase in cortisol during fasting are multifaceted. One study found that a 5-day fast led to a 1.8-fold increase in the 24-hour endogenous cortisol production rate in healthy men. This increase was primarily due to a higher mass of cortisol secreted per burst, rather than changes in the frequency or duration of cortisol secretory bursts. Additionally, fasting delayed the time of maximal cortisol concentrations to the early afternoon, indicating a shift in the diurnal pattern of cortisol secretion.
Interestingly, the response to fasting appears to differ between men and women. In a study examining the effects of a 10-day fast, significant increases in free cortisol and the free-to-total cortisol ratio were observed in men but not in women . This sex-specific response suggests that hormonal and metabolic differences may influence how fasting affects cortisol production.
Animal studies provide further insights into the effects of fasting on cortisone production. In ovariectomized rats, fasting significantly increased plasma corticosterone levels and enhanced the responsiveness of zona fasciculata-reticularis cells to adrenocorticotropic hormone (ACTH) stimulation. This increase was mediated through enhanced cAMP accumulation and the activity of L-type calcium channels, as well as increased expression of steroidogenic enzymes. These findings highlight the complex regulatory mechanisms involved in cortisone production during fasting.
Fasting not only increases cortisol levels but also disrupts the synchrony between cortisol and other hormones. In women, short-term fasting amplified cortisol secretion and disrupted the physiological coupling between cortisol and hormones such as growth hormone (GH), luteinizing hormone (LH), and leptin. This disruption indicates that fasting-induced stress can have broader implications for hormonal balance and metabolic regulation.
Intermittent fasting significantly impacts cortisone production by increasing cortisol levels and altering the balance between cortisol and cortisone. These effects are mediated through various mechanisms, including increased cortisol secretory burst mass and changes in hormonal synchrony. The response to fasting is also influenced by sex, with men showing a more pronounced increase in cortisol levels compared to women. Understanding these dynamics is crucial for evaluating the broader health implications of intermittent fasting and its role in stress and metabolic regulation.
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