Thursday, January 6, 2011

Overeating knocks out growth hormone release by Jerry Brainum

Several factors are known to boost the release of growth hormone(GH). These include intense exercise, particularly of larger muscle groups with enough intensity to produce a high lactic acid level;hypoglycemia; and certain amino acids, such as arginine when provided intravenously in doses of about 30 grams. There are also factors known to blunt GH release, such as obesity, and ingestion of a high fat or sugar intake. A new study examined the effects of overeating for two weeks in 7 non-obese men, average age, 25. These men entered a matabolic ward at a hospital, and stayed there for the entire course of the 2-week study, so that every morsel of food they ingested was monitored. An important point is that none of the subjects were obese, since obesity alone is known to blunt GH release, as is advanced age (over 40).
     The men consumed diets averaging 4,000 calories a day for 2 weeks, which was considerably above their metabolic needs, and they did no exercise. Baseline levels of GH and insulin were recorded at the start of the study. After three days of overeating, the subjects' GH levels declined by 80% compared to baseline. This drop occurred despite no weight gain at that point in the study. The men's 24-hour insulin levels doubled over baseline, which isn't surprising considering their high food intake. By the 2-week mark, the men's bodyweight had increased significantly, and bodyfat levels rose by 10%, but this increased weight and fat didn't lead to a further suppression of GH release than was noted after the third day.
    The high food intake resulted in a doubling of resting insulin levels, which effectively suppressed GH release in the men. Whether exercise would have made a difference wasn't examined in this study, but odds are that it would have, at least to a small extent. The significance of this study is that many people overeat in a similar manner all the time, resulting in a nearly total blunting of GH release. The lack of GH release in such people exacerbates the existing obesity, and also leads to greater visceral (deep abdominal fat) deposits, which can lead to onset of the metabolic syndrome, diabetes, and heart disease.

Cornford, A, et al. Rapid suppression of growth hormone concentration by overeating: Potential mediation by hyperinsulinemia.J Clin Endocrin Metab 2011: in press.

©,2012 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited

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