This is not meant to be a comprehensive guide to growth hormone function in the face of diet and exercise. Rather, I’m going to suss out some of the misconceptions that clients are laboring under, based on some questions I’ve recently had.
Growth hormone (GH) is a hormone which has an effect on both tissue growth and fuel mobilization. GH is released in response stressors like exercise, reductions in blood glucose, and both carb restriction or fasting. Shock of shocks, GH is a growth promoting hormone, increasing protein synthesis in the muscle and liver. GH can only carry out these actions through Insulin-Like Growth Factor 1 (IGF-1), which it stimulates the liver to release in the presence of insulin. To put it another way: high GH without high insulin equals little to no IGF-1.
So what about GH as it pertains to training and recovery? Well, before I get into research on how GH is released throughout the day and in response to training, I want you to know that at the end of this article I attached a list of studies that show the result of injecting GH on muscle mass and performance. Give it a look after this article.
So training does result in a GH increase. In fact it’s big in untrained subjects (10 fold increase above baseline), it’s not quite as big in trained guys (4-5 fold increase) (1,2). The thing is that it’s super brief, like back to baseline levels in an hour brief (3). Sounds great though, right? Five times higher than baseline? Here’s the thing: GH released during sleep is up to 20 times above baseline and lasts a lot longer, up to 3 hours (4). Finally, I’ll just quote this meta analysis on the subject of GH and athletics:
Claims that growth hormone enhances physical performance are not supported by the scientific literature.
What about GH’s role in fat loss? Doesn’t GH need to be elevated to move fatty acids for energy use? Well, take a look at this study of individuals with hyperinsulimia in which they lost 20lbs in 60 days. The drastically elevated insulin *should* have blunted the GH, which *should* have trapped the FFA’s for all eternity…but it didn’t seem to matter because they were eating less. This is why all of those “GH Diet” scams are successful: if your calories are low enough AND you’re injecting GH you’ll lose a bunch of fat. But it’s the low calories that let this happen, not the GH per se.
But I hear you all the way through the internet: I want to make sure I get whatever tiny cookie of benefit GH has to offer…should I avoid carbs after a workout to keep GH high?
Did a caveman tell you this? I really with this paleo myth would die, be buried, and be discovered by Jack Horner’s great^20 grandchild as an anthropological study of how little we knew.
Here’s the thing: GH is made higher post workout with the inclusion of carbs. So am I suggesting a big huge spike in insulin, meaning a metric ton of carbs post workout? Nay, but since you no longer have to worry about blunting GH, why not ensure protein synthesis occurs? A very small increase in insulin is needed to start protein synthesis, which is to say that a whey shake would get the job done very adequately.
Books have been written on this subject, but there’s not been Earth-shattering changes to this suggestion: if muscle gain and recovery are really really important to you, just eat a nice meal sometime soon after you train. You don’t have to rush it either; the post-workout window of opportunity is large enough to drive a truck through…just don’t decide to fast for 16 hours after the workout and you’ll cover your bases
Skyler Tanner is an Efficient Exercise Master Trainer and holds his MS in Exercise Science. He enjoys teaching others about the power of proper exercise and how it positively affects functional mobility and the biomarkers of aging.
This list is long and I thank Lyle McDonald for compiling it:
1: Phys Ther. 1999 Jan;79(1):76-82.
Does growth hormone therapy in conjunction with resistance exercise increase
muscle force production and muscle mass in men and women aged 60 years or older?
Zachwieja JJ, Yarasheski KE.
Exercise and Nutrition Program, Pennington Biomedical Research Center, Baton
Rouge, La., USA.
Improved muscle protein mass and increments in maximum voluntary muscle force
have rarely been observed in men and women aged 60 years and older who were
treated with rhGH. Although rhGH administration has been reported to increase
lean body mass in older men and women, it is doubtful that this increase is
localized to skeletal muscle contractile proteins. When rhGH administration was
combined with 16 weeks of resistance exercises, increases in muscle mass, muscle
protein synthesis, and muscle force were not greater in the rhGH-treated group
than in a weight training group that received placebo injections. Side effects of
rhGH treatment in elderly people are prevalent, not trivial, and further limit
its usefulness as an effective anabolic agent for promoting muscle protein
accretion in men and women. In particular, the induction of insulin resistance
and carpal tunnel compression reduces the efficacy of rhGH replacement therapy in
elderly individuals. The evidence for a GH-induced increase in human skeletal
muscle protein and maximum voluntary muscle force is weak. The optimum dose and
GH-replacement paradigm (GHRH, GH-secretagogues) have not been identified.
Whether rhGH therapy improves muscle protein mass and force in individuals with
severe cachexia associated with major trauma, burns, surgery, or muscular
dystrophy is controversial and under investigation.
2. Growth hormone effects on metabolism, body composition, muscle mass, and
Metabolism Division, Washington University School of Medicine, St. Louis,
It is clear that the anthropometric ramifications, especially with respect to
muscle mass, of the metabolic actions of GH and IGF-I treatment in intact and
GH-deficient adults require further study. At present, it appears that daily GH
or IGF-I treatment modestly increases nitrogen retention in most normal adults,
probably by separate but permissive mechanisms, but only for a short period of
time (approximately 1 month). During prolonged GH administration, resistance to
the anabolic actions of GH seems to occur, and optimizing the anabolic effects of
GH or IGF-I treatment will require a better understanding of the interactions
among GH, GHBP, IGF-I production, IGFBPs, the GH dose regimen, and other
unidentified regulatory factors. On the basis of the similar increases in muscle
protein synthesis, muscle cross-sectional area, and muscle strength observed in
placebo and GH-treated exercising young adults, it is doubtful that the nitrogen
retention associated with daily GH treatment results in an increase in
contractile protein, improved muscle function, strength and athletic performance.
Even in catabolic or GH-deficient populations, GH treatment provides only modest
increments in nitrogen retention, muscle size, strength, and exercise capacity.
Further, the side effects of GH treatment (water retention, carpal tunnel
compression, insulin resistance) would be a detriment, rather than an aid, to
athletic performance. In addition, whether prolonged (> 6 months) GH treatment
alone or in combination with other agents used by athletes (e.g., anabolic
steroids, beta-agonists) is associated with other adverse side effects (e.g.,
cancer, diabetes) has not been evaluated. Therefore, health professionals should
continue to discourage the use of GH by exercise enthusiasts.
3: Short-term growth hormone treatment does not increase muscle protein synthesis in
experienced weight lifters.
Yarasheski KE, Zachweija JJ, Angelopoulos TJ, Bier DM.
Metabolism Division, Washington University School of Medicine, St. Louis,
The purpose of this study was to determine whether recombinant human growth
hormone (GH) administration enhances muscle protein anabolism in experienced
weight lifters. The fractional rate of skeletal muscle protein synthesis and the
whole body rate of protein breakdown were determined during a constant
intravenous infusion of [13C]leucine in 7 young (23 +/- 2 yr; 86.2 +/- 4.6 kg)
healthy experienced male weight lifters before and at the end of 14 days of
subcutaneous GH administration (40 microgram.kg-1 x day-1). GH administration
increased fasting serum insulin-like growth factor-I (from 224 +/- 20 to 589 +/-
80 ng/ml, P = 0.002) but did not increase the fractional rate of muscle protein
synthesis (from 0.034 +/- 0.004 to 0.034 +/- 0.002%/h) or reduce the rate of
whole body protein breakdown (from 103 +/- 4 to 108 +/- 5 mumol.kg-1 x h-1).
These findings suggest that short-term GH treatment does not increase the rate of
muscle protein synthesis or reduce the rate of whole body protein breakdown,
metabolic alterations that would promote muscle protein anabolism in experienced
weight lifters attempting to further increase muscle mass.
4: Am J Physiol. 1992 Mar;262(3 Pt 1):E261-7.
Effect of growth hormone and resistance exercise on muscle growth in young men.
Yarasheski KE, Campbell JA, Smith K, Rennie MJ, Holloszy JO, Bier DM.
Department of Medicine, Washington University School of Medicine, St. Louis,
The purpose of this study was to determine whether growth hormone (GH)
administration enhances the muscle anabolism associated with heavy-resistance
exercise. Sixteen men (21-34 yr) were assigned randomly to a resistance training
plus GH group (n = 7) or to a resistance training plus placebo group (n = 9). For
12 wk, both groups trained all major muscle groups in an identical fashion while
receiving 40 micrograms recombinant human GH.kg-1.day-1 or placebo. Fat-free mass
(FFM) and total body water increased (P less than 0.05) in both groups but more
(P less than 0.01) in the GH recipients. Whole body protein synthesis rate
increased more (P less than 0.03), and whole body protein balance was greater (P
= 0.01) in the GH-treated group, but quadriceps muscle protein synthesis rate,
torso and limb circumferences, and muscle strength did not increase more in the
GH-treated group. In the young men studied, resistance exercise with or without
GH resulted in similar increments in muscle size, strength, and muscle protein
synthesis, indicating that 1) the larger increase in FFM with GH treatment was
probably due to an increase in lean tissue other than skeletal muscle and 2)
resistance training supplemented with GH did not further enhance muscle anabolism
5: Growth hormone and body composition in athletes.
Department of Pediatrics, University of Vienna, Austria. firstname.lastname@example.org
The anabolic properties of growth hormone (GH) have been investigated extensively. The effects of GH on normal, hypertrophied and atrophied muscles have been studied previously in animal experiments that demonstrated an increase in muscle weight and size, but no comparable increase in performance or tension. In adults with GH deficiency, the changes in body composition can be corrected by GH treatment; lean body mass and strength increase within a few months. In children with GH deficiency, Turner’s syndrome or intrauterine growth retardation, an increase in muscle tissue is seen after treatment with GH. In acromegalics with long-standing GH hypersecretion, the muscle volume is increased, but muscle strength and performance are not improved. These observations gave rise to the interest shown by healthy subjects and athletes in using GH to increase their muscle mass and strength. The improvements in muscle strength obtained by resistance exercise training in healthy older men or young men were not enhanced by additional administration of GH. The larger increases in fat-free mass observed in the GH-treated groups were obviously not due to accretion of contractile protein, but rather to fluid retention or accumulation of connective tissue. In experienced weightlifters, the incorporation of amino acids into skeletal muscle protein was not increased and the rate of whole body protein breakdown was not decreased by short-term administration of GH. The results of a study in power athletes confirm the results of these investigations. The study used GH treatment in power athletes compared with a placebo-control group, and the results indicated no increase in maximal strength during concentric contraction of the biceps and quadriceps muscles, although levels of insulin-like growth factor-I were doubled. In highly trained power athletes with low fat mass and high lean body mass, no additional effect of GH treatment on strength is to be expected.