Growth hormone (GH), as the name suggests, regulates metabolism and energy utilization in the body by promoting muscle mass building, bone health and wound healing. It coordinates with other hormonal effectors like insulin and insulin-like growth factor-1 (IGF-1) to regulate carbohydrate and fat metabolism, leading to somatic growth.
Growth hormone stimulates lipolysis by activation of the enzyme, lipase. This results in the efflux of free fatty acids from the visceral adipose tissue into the blood circulation. Mobilization of fat stores thus enables fat utilization for energy production and more fat loss as a result (1).
Growth hormone & obesity: A vicious crosstalk
Growth hormone levels are significantly reduced in obese individuals (2). The presence of low growth hormone actually magnifies the effects of insulin, as under normal conditions these two hormones antagonize each other (3). Thus, insulin resistance or high insulin levels, a marker of chronic obesity, is allowed to develop unchecked as a result of lower than normal GH levels. This combination of insulin resistance and low GH secretion is the reason behind the accumulation of visceral fat and abdominal fat in obese individuals. In one study, people at a normal body weight subjected to two weeks of over-eating were found to have lower levels of GH without significant changes in body weight. This implies that reduction in GH is both the cause and consequence of obesity (4).
In addition, leptin resistance associated with obesity also impairs normal secretion of GH (5), creating a vicious crosstalk between insulin resistance, leptin resistance, and low GH secretion, all of which spur fat accumulation and further exacerbate obesity.
Growth hormone treatment for obesity
In a study dating back to 1999 (6), obese individuals undergoing low-dose growth hormone therapy in addition to a low-calorie diet reported experiencing accelerated fat loss in the viscera and increased lean body mass. In a 2005 clinical trial (7), 12-month treatment of GH improved insulin response in postmenopausal women with visceral obesity, and not only reduced abdominal fat but also improved low-density lipoprotein (bad cholesterol) levels. A more recent meta-analysis (8) had a different theory to put forward- In individuals receiving growth hormone injections, a change in body composition was observed, involving conversion of adipocyte tissue to the muscle mass; however, weight remains unchanged. It must be noted that the World Health Organization (WHO) has not yet given approval for therapeutic administration of HGH for weight loss. However, what these studies do indicate is that increasing growth hormone levels naturally in the body using a combination of diet and a healthy lifestyle can greatly help modify body composition on your journey towards a more normal weight.
Dietary choices to increase GH
In the light of the above observations, collated from vast range of studies, the benefits of adopting healthy dietary practices in restoring normal secretion of GH for achieving a healthy body weight have become increasingly clear. Let’s look at some of these:
- Melatonin-rich foods: asparagus, raspberries, tomatoes, pomegranate, grapes, cucumber, nuts, seeds
- Vitamin D-rich foods: Salmon, mackerel and other oily fish, egg yolks,
- L-arginine-rich foods: soybeans, pumpkin seeds, turkey, peanut butter, steak
Daily practices to raise GH levels
- Intermittent fasting
Fasting provokes an intriguing metabolic response within the body, involving an increase in the levels of growth hormone (9) and mobilization of free fatty acids (10). A 24-hour fast has been found to increase circulating levels of GH by manifold (11). What’s more interesting is that growth hormone released during fasting specifically induces lipolysis, i.e. breakdown of fat while preserving muscle proteins from undergoing breakdown (12). In other words, it’s safe to say that you don’t have to worry about losing muscle when you exercise during a fast. In fact, the combination of two potent stimuli- fasting and exercise will only increase GH levels significantly, leading to faster fat loss.
- Eating dinner early
Growth hormone release follows a specific circadian rhythm, meaning its levels are low during the day and only peak at night (13). Both the depth and duration of non-REM sleep regulates the release of GH-releasing hormone (GHRH) from the hypothalamus (14). As eating food generally spikes insulin levels, having a late dinner and sleeping soon thereafter maintains insulin levels high all night, preventing the timely release of GH. As such it’s advisable to wait an hour or two post-dinner before hitting bed.
- Minimizing sugar intake
Overindulgence of processed foods with added sugar that exceed the daily limit of 25 grams increases insulin levels, leading to impaired secretion of GH from the pituitary (15). Practicing portion control is a must when eating such foods as growth hormone and its anabolic effects on muscle building and body composition will be completely missed out.
- Getting more sleep
As discussed above, growth hormone peak reaches when you enter a deep, undisturbed state of slow-wave sleep (SWS). As such, it’s essential to ensure a good 7-8 hours of sound sleep (16). Consider drinking milk after dinner to ensure effective release of melatonin- the sleep-inducing hormone. Additionally, keep bedroom temperatures low and wear light, airy clothes that allow free flow of circulation.
Besides sleep, the second most potent non-pharmacological stimuli for GH release is exercise. In women performing aerobic exercise, exercise-induced growth hormone response (EIGR) was found to increase GH levels by 2-fold in 24-hour. However, this was observed only when training intensity was above the lactate threshold (17). Similarly, only 10 minutes of high-intensity exercise led to an elevation in hGH levels (18). Both low and heavy-volume resistance training that engaged multiple muscle groups at once led to a significant growth hormone response (19, 20).
In short, when it comes to cardio, it’s the intensity rather than duration that induces GH responses, while in case of resistance training, all three factors, intensity, frequency and duration help determine GH release.