Monday, 18 April 2016


Six normal adult men were put is a study where they were examined during a 5 day fast and during a feeding day. They were thoroughly observed on the first and last day of the 5 day fast. The main aim of these study was to determine how intermittent fasting affects the growth hormone (GH). The results were c onclusive

Rats have show in studies that they release GH every 3-4 hours which is consistant with the ultradian pattern, unfortunately humankind has shown inconsistent and erratic  release of the growth hormone.

One reason for this varying release of the growth hormone is because of the type of food we eat as this has an effect on GH secretion. In particular “glucose and fatty acids suppress GH release while certain amino acids stimulate secretion”

Fasting counteracts this by lowering somatomedin C levels and removing the feedback inhibition of GH release.” This open-loop system would be predicted to elevate basal GH concentrations and allow identification of spontaneous pulsatility with greater accuracy.”


The methods used in this study




Six normal healthy male volunteers (ages 21-36 yr) of normal body weight (BMI 21.8-28.0 kg/m2) were studied. Each subject gave written informed consent, approved by the Human Investigation Committee of the University of Virginia School of Medicine. All subjects had normal sleep habits, had not taken any transmeridian fights within the previous 4 week, and were not taking any medication.


Study design


Each subject was studied on three occasions during which blood samples

were obtained every 20 min over a 24-h period. These studies were

undertaken during (a) a control fed day, in which three meals were

served at 0900, 1300, and 1800 hours, and on (b) the first and (c) fifth

days of a 5-d fast in which only water, potassium chloride (20 meq/d),

and vitamin supplements (I multivitamin capsule/d) were given. In

three subjects, the control fed study was performed before the two

fasted studies, while in the remaining three, the control study was

undertaken last. A period of 2 wk separated the fed and the fasted

studies. The subjects were admitted to the Clinical Research Center at

0700 hours and a cannula with a heparin lock was inserted into a

forearm vein. A 1-h period was allowed before commencement of the

studies at 0800 hours. Subjects were encouraged to ambulate on study

days and daytime naps were prohibited. Sleeping was permitted after

2200 hours and the period of sleep recorded by the ward staff. An

intravenous bolus dose of I jAg/kg GHRH-40 was administered at the

end of each of the three 24-h studies, and blood sampling continued at

the same frequency for a further 3 h. Blood samples for glucose, free

fatty acids, ,B-hydroxybutyrate, acetoacetate, somatomedin C (SmC),

and blood biochemistries were obtained during the 5-d fast. Subjects

were also weighed daily and a urine analysis performed daily for urinary




Samples from each individual’s three studies (n = 72 + 9 for each

study) were run in triplicate in the same assay. GH was measured using

the Nichols Institute (San Juan Capistrano, CA) hGH immunoradiometric

assay which was modified to enhance the limit of sensitivity to

0.2 ng/ml. The intraassay coefficients of variation were 6.3, 6.4, and

3.9% at 4, 7.3, and 19.8 ng/ml, respectively. The interassay coefficients

of variation were < 9.2% at the above levels. Blood glucose was measured

using the glucose oxidase method and a glucose analyzer (Beckman

Instruments, Fullerton, CA) (15). SmC, unesterified fatty acids,

acetoacetate, and ,#-hydroxbutyrate concentrations were measured

using methods as previously described (16, 17) and as adapted from

reference 18.”



in conclusion the growth hormone is affected by fasting, but the fasting doesnt have to be for 5 days for it to be effective. the effect can take place in as little as 12 -24 hours

the research can be accessed here



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