Does fasting increase testosterone? Well, let’s take a look. Testosterone influences muscle mass, bone density, fat distribution, and libido, making it a key indicator for men’s overall health and performance markers. The relationship between fasting and testosterone levels, however, is what I would consider a grey area. Testosterone levels are influenced by several factors including the duration of the fast, the individual’s baseline health and body composition, and even the timing of food consumption during non-fasting periods.
Outline:
- How Testosterone is Regulated During Fasting
- Hypothalamic-Pituitary-Gonadal (HPG) Axis
- Long Term vs Short Term on Testosterone
- Growth Hormone Implications
- Short Term vs Long Term
- Notes
- References
How Testosterone is Regulated During Fasting
During fasting, the body undergoes several hormonal and metabolic adjustments to conserve energy and protect vital organs. These adjustments can have a direct or indirect impact on testosterone levels. One primary way is in the hypothalamic-pituitary-gonadal (HPG) axis, which is crucial for regulating testosterone production.
First things first, what is the hypothalamic-pituitary-gonadal (HPG) axis? Simply put, this is made up of three parts:
- Hypothalamus: I am not a scientist, and you could write an entire book on this one region, but for today, we are primarily focused on its part in producing gonadotropin-releasing hormone (GnRH).
- Pituitary gland: I am sure everyone has heard of this gland. This gland produces several key hormones in our body. Today we are focused on Growth Hormone (GH) and Luteinizing Hormone (LH) with regards to testosterone production.
- Gonads: Yea, you know about these right? Our primary reproductive organ. In the context of this topic, this is the last stop of the process, or at least where testosterone is secreted.
It looks something like this; the hypothalamus secretes gonadotropin-releasing hormone (GnRH) when then stimulates the pituitary gland to release luteinizing hormone (LH) when then travels down to the testes (gonads) where Leydig cells are stimulated to produce testosterone.
So how does fasting affect this system?
Effects on Hypothalamus and GnRH Secretion
- Energy Availability: Fasting decreases energy availability, which the hypothalamus detects. In response to perceived energy scarcity, the hypothalamus may reduce the amplitude and frequency of gonadotropin-releasing hormone (GnRH) pulses. This reduction is a part of the body’s broader effort to conserve energy by temporarily downregulating energy-intensive processes, such as reproduction.
- Stress Response: Fasting can initiate a stress response, leading to increased secretion of corticotropin-releasing hormone (CRH) from the hypothalamus. CRH and the resulting increase in cortisol can inhibit GnRH secretion, as stress hormones generally have a suppressive effect on the reproductive axis.
Effects on the Pituitary Gland:
- Reduced GnRH pulses lead to decreased stimulation of the pituitary gland, resulting in lower levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. These hormones are crucial for stimulating the gonads to produce sex hormones and gametes (sperm in men and eggs in women). A decrease in LH and FSH can lead to reduced testosterone production in men and altered estrogen and progesterone levels in women, affecting fertility and other aspects of reproductive health.
Influence on the Gonads:
- In turn, the reduced GnRH leads to decreased LH levels as mentioned above when then decreases testosterone production by the Leydig cells.
However, it is not this cut and dry. As mentioned, the type of fast (length, duration, etc) is a vital part of the equation.
Long-term vs. Short-term Fasting
- Short-term Fasting: Acute or short-term fasting may have minimal or transient effects on the HPG axis, with the body quickly returning to normal function once regular eating resumes.
- Long-term Fasting or Chronic Caloric Restriction: Prolonged fasting or chronic caloric restriction can have more significant and lasting effects on the HPG axis, potentially leading to reduced sex hormone levels, decreased libido, fertility issues.
Adaptation and Individual Variability
The body can adapt to fasting, and the initial suppressive effects on the HPG axis may diminish with regular fasting practices, such as those seen in intermittent fasting protocols. Individual responses can vary widely based on genetic factors, body composition, overall health, and the specifics of the fasting regimen.
But Wait There is More!
There are numerous studies that show fasting releases Growth Hormone (GH). Here is how:
Mechanisms Behind GH Increase During Fasting
- Energy Conservation and Mobilization: Fasting triggers the body to conserve energy and mobilize stored nutrients. GH promotes lipolysis, the breakdown of fats into free fatty acids for energy, preserving muscle and bone tissue by making energy stores available. This process is crucial during fasting when glucose availability is reduced.
- Stress Response: Fasting induces a mild stress response, leading to increased secretion of ghrelin (a hormone that stimulates hunger and GH release) and decreased insulin levels. Both changes contribute to elevated GH secretion. The decrease in insulin levels is particularly significant because insulin can suppress GH release. Lower insulin levels during fasting remove this inhibitory effect, allowing GH levels to rise.
- Enhanced GH-Releasing Hormone (GHRH) Efficacy: Fasting may enhance the effectiveness of GH-releasing hormone from the hypothalamus, further promoting GH secretion by the pituitary gland.
Effects of Increased GH During Fasting
- Fat Loss: Increased GH levels enhance the breakdown of triglycerides and suppress their accumulation in fat tissues, facilitating fat loss.
- Muscle Preservation: GH helps protect and preserve muscle mass during fasting by promoting the mobilization of fatty acids for energy instead of amino acids from muscle proteins.
- Metabolic Rate: GH can increase the basal metabolic rate, helping the body burn more calories even at rest. This effect contributes to the energy mobilization necessary for sustaining basic physiological functions during periods of reduced food intake.
- Cellular Repair and Longevity: Fasting-induced GH spikes may accelerate cellular repair processes, including autophagy, where cells digest and remove old and dysfunctional proteins. This mechanism is linked to improved health outcomes and longevity.
Short-term vs. Long-term Fasting
- Short-term Fasting: Acute or short-term fasting (24–48 hours) has been shown to significantly increase GH levels. This increase can be rapid and is part of the body’s immediate response to the lack of nutrient intake.
- Long-term Fasting and Intermittent Fasting: Prolonged fasting or intermittent fasting regimens can lead to repeated bouts of increased GH secretion. Over time, this can enhance the body’s overall metabolic efficiency and health, although the specific patterns and magnitude of GH release can vary based on the fasting duration and individual metabolic differences.
Other Notes
Fasting also, if done properly, decreases body fat which numerous studies show that less body fat in men is correlated with increased testosterone levels. Body fat, particularly visceral fat, which accumulates around the abdominal region, has a significant impact on hormone balance, including the levels of testosterone.
There does not appear to be any research that looks at all of this data in whole and we are piecing this information together, but from what I have researched, I gather that over all yes, fasting protocols can increase your testosterone over the long-term. However, as previously mentioned, it will take some well-thought-out plans specifically tailored to one’s genetic predisposition.
References
- Fontana, L., & Klein, S. (2007). Aging, adiposity, and calorie restriction.
- Martin, B., Mattson, M.P., & Maudsley, S. (2006). Caloric restriction and intermittent fasting: Two potential diets for successful brain aging.
- Tinsley, G.M., & La Bounty, P.M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans.
- Wegman, M.P., Guo, M.H., Bennion, D.M., Shankar, M.N., Chrzanowski, S.M., Goldberg, L.A., Xu, J., Williams, T.A., Lu, X., Hsu, S.I., Anton, S.D., Leeuwenburgh, C., & Brantly, M.L. (2015). Practicality of intermittent fasting in humans and its effect on oxidative stress and genes related to aging and metabolism.
- Auchus, R.J., & Rainey, W.E. (2004). Adrenarche – Physiology, biochemistry and human disease.
- Hartman, M. L., Veldhuis, J. D., Johnson, M. L., Lee, M. M., Alberti, K. G., Samojlik, E., & Thorner, M. O. (1992). Augmented growth hormone (GH) secretory burst frequency and amplitude mediate enhanced GH secretion during a two-day fast in normal men.
- Vendelbo, M. H., Jørgensen, J. O. L., Pedersen, S. B., Gormsen, L. C., Lund, S., Schmitz, O., Jessen, N., & Møller, N. (2012). Exercise and fasting activate growth hormone-dependent myocellular signal transducer and activator of transcription-5b phosphorylation and insulin-like growth factor-I messenger ribonucleic acid expression in humans.
- Ho, K. Y., Veldhuis, J. D., Johnson, M. L., Furlanetto, R., Evans, W. S., Alberti, K. G. M. M., & Thorner, M. O. (1988). Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man.
- Longo, V. D., & Mattson, M. P. (2014). Fasting: Molecular mechanisms and clinical applications.
- Areta, J. L., & Hopkins, W. G. (2018). Skeletal muscle anabolism following resistance training: Roles of protein synthesis, mTORC1, and satellite cells.
Disclaimer:
This information is for informational purposes only. This is not medical advice. Always seek the help of your healthcare provider.