As legend (or myth) would have it, 16th century explorer Juan Ponce de León came to America in search of the “fountain of youth.” While we know there’s no such “fountain” down in Florida, some would suggest that such a magic elixir can be found inside the human body. Growth Hormone!
Indeed, growth hormone has been referred to as the “fountain of youth” and a key anti-aging hormone.
Growth hormone levels are high early in life, corresponding to the period of rapid growth, and they begin to decline after attainment of adult body size and full physical and reproductive maturation.
This decline continues during adult life and aging, and not surprisingly, growth hormone levels in older folks are substantially lower than young adults.
The age-related decline in growth hormone (and its associated hormones) has been referred to as “somatopause” in analogy with menopause and andropause, the agerelated decline in sex hormones in women and men, respectively.
Somatopause is associated with several very important characteristics of aging:
- Decreased muscle mass
- Increased body fat (particularly abdominal fat)
- Reduced libido
- Decreased energy levels
- Thinning skin
There’s no question that among the most well-known functions of growth hormone are increased fat breakdown and utilization and increased protein synthesis.
Numerous studies have shown that growth hormone therapy decreases the signs of biological aging in folks who are deficient.
Treatment has been shown to improve body composition (reduce body fat, increase muscle mass), increase bone density, and increase skin thickness.
While growth hormone typically gets all the publicity, many of its biological effects are mediated by its stimulation of the production of another hormone secreted by the liver called insulin-like growth factor 1 (IGF-1), which is referred to as the “key mediator of GH action.”
For instance, IGF-1 is an important stimulant of protein synthesis in muscle (i.e., repairing and building muscle), and it also stimulates free fatty acid utilization (i.e.,fat burning).
What’s more, IGF-1 is associated with reduced skin wrinkling and a lower perceived age.
While the impending future of somatopause sounds very bleak, the great news is that there are several controllable lifestyle factors that can have a tremendous impact on growth hormone production. We’ll explore each of these in more depth below.
Arguably the most important factor involved in optimizing growth hormone output is sleep.
Growth hormone is secreted from the anterior pituitary gland in a pulsatile manner, and up to 8 to 10 “pulses” of growth hormone are secreted in a 24-hour period.
Despite its pulsatility, a seminal study published in 1968 established that growth hormone levels peak during sleep; more precisely, researchers demonstrated that peak growth hormone levels reach their highest values within 1 to 2 hours after the onset of sleep (between 11pm and 12am).
Delaying the onset of sleep results in the delayed secretion and lower peak levels of growth hormone.
In addition to sleep timing, poor sleep can also reduce the amount of growth hormone the body produces.
Clearly, sleep is important for optimal growth hormone levels.
Along those lines, melatonin is a hormone produced by the pineal gland that causes sleepiness.
In other words, melatonin is a sleep facilitator.
While that alone may benefit higher growth hormone levels, additional research has shown that melatonin plays a direct role in regulating and increasing growth hormone secretion.
Below, we’ll cover some foods that may promote melatonin production and better sleep.
For now, here are some tried and true strategies to optimize sleep:
- Get outside and spend more time in the sunlight during the day. Getting plenty of sunlight exposure, especially early in the day, helps set circadian rhythms (i.e., melatonin).
- Conversely, limit exposure to blue light (e.g., TV, computer, phone, and tablet screens) after the sun goes down. High-energy blue light from devices can disrupt circadian rhythms and suppress melatonin production.
- Believe it or not, caffeine is not a sleep aid; it literally blocks sleep. For most folks, it’s a good idea to avoid caffeine within 8 – 10 hours of bedtime. Researchers at Michigan’s Henry Ford Hospital’s Sleep Disorders and Research Center and Wayne State College of Medicine found that caffeine consumed even 6 hours before bedtime resulted in significantly diminished sleep quality and quantity.
- Sleep experts suggest that the ideal bedroom temperature ranges between 60 and 67 degrees. Because your body temperature naturally cools to initiate falling asleep, keeping the bedroom cooler can help facilitate sleep.
- Make your bedroom as dark as possible. Artificial light (e.g., alarm clocks, TV screens, night lights) after dark can send wake-up signals to the brain, suppressing the production of the sleep-inducing hormone melatonin, making it harder to fall asleep and stay asleep.
- Create a relaxing bedtime ritual and begin winding down 1 – 2 hours before you want to go to sleep. This may involve drinking some relaxing tea, reading a book, meditating, doing some relaxing stretches, etc. The goal is to reduce stress and anxiety and help prepare your mind and body for sleep.
- Conduct a “mind dump.” For many people, as soon as their head hits the pillow, their minds race 100 miles per hour. Rather than keeping yourself awake “wondering and worrying,” write down what’s on your mind in a notebook, which you can keep by your bedside. This will help you remember anything that’s truly important. Perhaps even more importantly, this can help you realize that there’s probably nothing that you can do about many of these things at that very moment.
- Get moving. Regular exercise helps normalize circadian rhythms, optimize hormone levels, and regulate the sympathetic nervous system. In general, daytime exercise has a positive effect on nighttime sleep quality. It is generally recommended not to exercise within 2 – 3 hours of bedtime; however, while there is some research to corroborate that recommendation, the overall body of evidence does not completely support the notion that late-night exercise disturbs sleep quality.14–16 Overall, exercise is a good thing for sleep, and it’s up to your best judgement to choose the appropriate timing for you.
Speaking of exercise, besides sleep, it is the most effective tool to boost growth hormone levels.
In particular, resistance training results in the most significant exercise-induced growth hormone response.
Having said that, weight training workouts that are high in volume (high number of repetitions), moderate to high in intensity (> 60% 1RM), using short rest intervals, and stressing a large muscle mass (compound movements like squats, deadlifts, presses, and pulls) produce the greatest elevations in growth hormone.
Several studies have suggested an intensity “threshold” exists for exercise-induce growth hormone release.
An exercise intensity above lactate threshold (i.e., “feel the burn”) and for a minimum of 10 minutes appears to elicit the greatest release of growth hormone.
High-intensity interval training (HIIT), high-intensity resistance training (i.e., circuit training), metabolic resistance training, and barbell and dumbbell “complexes” are all excellent tools to boost growth hormone levels.
To find out more about these types of exercise, check out this article.
In an interesting study published in The Journal of Clinical Endocrinology & Metabolism, 18 healthy men, 65 to 82 years of age, underwent progressive strength training for 14 weeks, followed by an additional 10 weeks of strength training plus either growth hormone replacement or placebo.
In the study, resistance exercise training increased muscle strength significantly—the addition of growth hormone did not result in any further improvement.
Several other studies have corroborated these findings.
In young men, resistance exercise with or without supplemental growth hormone treatment resulted in similar increments in muscle size, strength, and muscle protein synthesis.
Another study in older men showed resistance exercise training improved muscle strength, but these improvements were not enhanced when exercise was combined with daily GH administration.
In other words, going to the gym is beneficial, and certainly cheaper, than growth hormone replacement.
Lose Body Fat
When it comes to growth hormone, body fat is a dual threat.
For starters, most people are familiar with the effects of growth hormone on fat metabolism.
Growth hormone predominantly stimulates the release of free fatty acids and increases fat burning.
Meanwhile, growth hormone spares calorie-burning lean body mass.
For anyone interested in dropping body fat and improving body composition, optimizing growth hormone is of obvious significance.
Therein lies the conundrum:
The amount of body fat you carry is directly related to how much growth hormone you produce, and the higher your body fat (particularly abdominal/visceral fat), the less growth hormone you produce.
That should come as no surprise, adults with low levels of growth hormone typically experience an increase in body fat accumulation; meanwhile, growth hormone replacement (in adults deficient in growth hormone) results in reduction in fat mass, and in particular, visceral fat (although the reductions are modest and similar to what can be achieved by diet and exercise).
The interesting thing is that excess body fat appears to directly suppress release of growth hormone.
On top of that, the growth hormone that is produced is cleared more rapidly in folks with high amounts of body fat.
Clearly, losing body fat has important implications for optimizing growth hormone output.
Indeed, research has shown that normal growth hormone levels can be restored in formerly obese folks following weight loss.
In evolutionary terms, growth hormone is viewed as the primary anabolic hormone during periods of stress and fasting.
During fasting, growth hormone secretion is amplified, and it stimulates the release of free fatty acids (a process called lipolysis) and increases fat burning.
Conversely, the presence of carbs and fats inhibits growth hormone release.
During fasting, growth hormone helps preserve calorie-burning muscle mass. Indeed, lack of growth hormone during fasting increases protein loss by as much as 50%, with a similar increase in muscle protein breakdown.
Similarly, growth hormone defends against hypoglycemia (during fasting) and helps support normal blood sugar levels.
In 1936, Bernardo A. Houssay recognized this role of growth hormone saying, “One of the most salient characteristics of pituitary insufficiency [growth hormone deficiency] is the tendency to hypoglycemia during fasting, which becomes manifest after a few hours.”
Several studies have shown that fasting enhances growth hormone secretion.
One study showed that five days of fasting resulted in a significant increase in growth hormone pulse frequency (↑70.7%), 24-hour growth hormone secretion (↑210%), and peak pulse level (↑108%).
Another study showed that just two days of fasting resulted in a 5-fold increase in growth hormone production, a 2-fold increase in the number of growth hormone pulses, and a 74.6% increase in the amount of growth hormone secreted per pulse.
While the good news is that fasting can enhance growth hormone production, the betternews is that you may not need to fast for days at a time.
In fact, a single day of fasting has been shown to lead to a pronounced increase in growth hormone output.
Along those lines, alternate-day fasting (ADF), which consists of a “fast day” alternated with a “fed day” may be a form of intermittent fasting conducive to boosting growth hormone levels.
One popular variation of ADF is The 5:2 Diet.
Time-restricted feeding (TRF), which involves consuming all food during a defined period of time (e.g., 4 – 8 hours), is the most popular form of intermittent fasting.
However, the evidence is less clear of the effects of TRF on growth hormone output.
One study showed that 8 weeks of TRF led to a significant decrease in IGF-1.
Because growth hormone was not measured and lower levels of IGF-1 can signal the body to produce more growth hormone (through a negative feedback loop), it’s difficult to draw any clear conclusions.
Speaking of fasting, it’s also worth pointing out that ghrelin, which is often viewed negatively as a “hunger hormone” that drives eating, actually goes by another name: growth-hormone releasing peptide.
That’s right, ghrelin stimulates the release of growth hormone.23 Along those lines, it’s not far-fetched to suggest that prolonging the time between meals may even have a beneficial effect on growth hormone output.
When it comes to nutrition, what you eat (and don’t eat) and when you eat may all play a role in the amount and pattern of growth hormone release.30 High levels of glucose and free fatty acids inhibit secretion of growth hormone. Conversely, hypoglycemia and ingestion of protein (high levels of circulating amino acids) stimulate the release of growth hormone.
Further, insulin has an antagonistic effect on growth hormone.
Taken together, it’s best to minimize consumption of refined carbohydrates and added sugars, which tend to have the greatest impact on blood glucose levels and insulin secretion.
Timing of feeding is also important. As you already know, while growth hormone is secreted in spurts throughout the day, the largest amount is released within the first hour or two after falling asleep.
With that in mind, it may be best to limit food intake before bed or even avoid consuming any food within a couple hours before bed, as the insulin response may inhibit growth hormone release.
At this point, the research is very limited, and this is mostly speculative.
Having said that, a recent study showed that consumption of 30 grams of milk-based protein (i.e., casein) within 30 minutes of sleep did not disrupt growth hormone output.
Along those lines, a small protein-rich snack an hour or so before bed may be beneficial for body composition, metabolism, and cardiometabolic health without any negative consequences on growth hormone output.
Theoretically, because amino acids stimulate the release of growth hormone, this practice could enhance production.
Now that we’ve touched on what and when not to eat, let’s dive into some foods and nutrients that may help support optimal levels of growth hormone.