Muscle hypertrophy from an integrative perspective

Posted by Simone do Carmo

Muscle hypertrophy is more than training and how many calories or grams of protein an athlete eats. The hormonal environment is also key. This blog article is a taster of my upcoming Module 2 lecture on the Certificate of Integrative Sports Nutrition course, so hopefully I can whet your appetite!

There are many reasons an athlete would want to grow more muscle – to improve their performance (increase strength and power) or aesthetics, or for general health reasons, especially Masters athletes, since the risk of age-related sarcopenia increases as we get older. Regardless of their reasons, muscle growth is basically an increase in the number of myofibrils (muscle fibres) and other non-contractile elements such as connective tissue and water content. But we need to go a bit deeper and consider two types of hypertrophy:

  • - Sarcoplasmic hypertrophy: an increase in the volume of sarcoplasmic fluid in the muscle cell and other non-contractile elements with no accompanying increase in muscular strength. This hypertrophy is seen in the typical ‘puffy’ look of bodybuilders. Although there is no concomitant increase in strength, the chronic cell swelling may lead to growth of the contractile proteins (actin and myosin).
  • - Myofibrillar hypertrophy: an increase in the size of contractile proteins (actin and myosin) with an accompanying increase in strength. This hypertrophy is seen in weightlifters and powerlifters with ‘denser’ and more ‘functional’ muscles.

Different mechanisms cause muscle growth. For example, several anabolic signalling pathways have been identified, including the well-known mTOR pathway, which is believed to be the master one. Certain hormones, such as testosterone, growth hormone, cortisol, etc., are also believed to influence muscle growth. However, a recent study even suggests that it’s not the higher post-training systemic testosterone or growth hormone levels that promote muscle growth, but the number of androgen receptors in the muscles that might explain why athletes respond so differently when training for muscle growth (1). More research is needed, but if hormones do play a role, no matter how small, our goal should be to support these for optimal muscle growth.

Let’s take testosterone as an example: a powerful androgen in humans that regulates many bodily functions, including muscle development, bone health, immune function, etc. So, instead of just focusing on the number of calories and protein needs, we also need to support testosterone through nutrition and lifestyle.

Often considered ‘bad’, cholesterol is required as it’s a precursor of testosterone and all other steroid hormones. Although our bodies can make cholesterol, when needed, an athlete can also obtain cholesterol mainly through animal-based foods. We also need to ensure that an athlete is eating sufficient healthy fats overall. In a randomised, crossover study, 60 young and healthy males consumed extra virgin argan oil or extra virgin olive oil for three weeks, with a stabilisation period of two weeks when they only consumed butter. Both types of oil significantly increased testosterone levels and luteinizing hormone, which stimulates Leydig cells to produce testosterone (2).

Minimising stress is a big factor. Chronically elevated cortisol levels will diminish testosterone as they both use the same ‘parent’ hormone called pregnenolone which is derived from cholesterol. The body will favour cortisol production if an athlete is subject to high stress, especially overtraining. High stress levels may also lead the athlete to make poor-quality food choices (high sugar and refined fats), potentially contributing to other health imbalances such as blood glucose dysregulation, the storage of visceral fat, poor gut health, etc., which, in turn, are likely to negatively affect their performance.

Vitamin D and zinc are also considered natural testosterone boosters. There is a strong association between vitamin D supplementation and testosterone levels in healthy men (3, 4). And a study in wrestlers revealed that a four-week zinc supplementation programme prevented the inhibition of both thyroid hormones and testosterone levels from exhaustion exercise (5).

Other strategies to support testosterone include high-quality sleep, avoiding xenoestrogens (oestrogen-like chemicals) like those found in plastic bottles, and some herbs like ashwagandha.

By taking these different strategies into account alongside the conventional focus on adequate resistance training and the quantitative aspect of what they need to eat, athletes will be improving their health and muscle growth at the same time.


  1. Morton, et al (2018). Muscle Androgen Receptor Content but Not Systemic Hormones Is Associated With Resistance Training-Induced Skeletal Muscle Hypertrophy in Health, Young Men. Front. Physiol. 9:1373.
  2. Derouiche A et al (2013). Effect or argan and olive oil consumption on the hormonal profile of androgens among healthy adult Moroccan men. Nat Prod Commun. 8(1):51-53.
  3. Wehr E et al (2009). Association of vitamin D status with serum androgen levels in men. Clin Endrocrinol (Oxf). 73(2):243-248.
  4. Pilz S et al (2011). Effect of vitamin D supplementation on testosterone levels in men. Horm Metab Res. 43(3):223-225.
  5. Kilic M (2006). The effect of exhaustion exercise on thyroid hormones and testosterone levels of elite athletes receiving oral zinc. Neuro Endocrinol Lett. 27(1-2):247-252.