Sunday, January 23, 2011

Growth hormone and fat loss


Some recent studies have suggested that the increase in some anabolic hormones through exercise, such as testosterone and growth hormone, is irrelevant for muscle growth purposes.Why this is so would require an entire article to be explained. But based on such assertions, it would be a rush to judgment to assume that an increase in such hormones through exercise is worthless. One example of this is a recent study that examined the effects of exercise on reductions in visceral body fat levels.
    Visceral body fat is fat located in the deep abdominal area. This particular fat store is considered especially dangerous because of its close association with the onset of cardiovascular disease, insulin resistance, and diabetes. One reason this is so is because visceral fat is constantly being released into the blood, where it travels to liver. Once in the liver, this fat acts as a substrate for the formation of cholesterol, while also contributing to the development of fatty liver.
    The new study involved 10 men and 9 women, all of whom were obese and had type-2 diabetes. Several of them were taking medication to treat diabetes and high blood pressure. They were randomly assigned to either an exercise group or a non-exercise group. Those in the exercise group did two 30-minute sessions of treadmill walking everyday in the morning and evening for a month. They used an intensity level equal to anaerobic threshold.This means that they exercised using a higher level of intensity, with the anaerobic threshold corresponding to the onset of production of higher levels of lactic acid in the working muscles. According to most exercise physiology textbooks, this is the point where fat oxidation decreases and the body relies more on glucose and glycogen to power exercise. In addition, such textbooks often point out that growth hormone (GH) release during exercise in the obese is blunted to the point of being nearly nonexistent.
     Despite these notable "facts," the subjects who did the exercise for a month showed a 21.7% drop in visceral body fat stores, while those who didn't exercise showed a 5.5% drop, likely because both groups also consumed a diet not exceeding 25 calories per kilogram of bodyweight. Levels of insulinlike growth factor-1 (IGF-1) increased in the exercise group by 5.8%, and 0.5% in the non-exercise group. IGF-1 is a measure of growth hormone release, thus indicating that those who exercised did indeed produce higher levels of GH.
     Textbooks say that to reduce fat requires a high output of catecholamines, such as epinephrine and norepinephrine as a result of exercise. Yet the level of intensity used in this study wasn't enough to boost levels of catecholamines. This shows that the reduction in visceral fat mass in the exercising subjects resulted from an increase in GH levels. Subcutaneous fat stores, or fat stores under the skin, weren't affected. Still, the most dangerous fat stores to health--visceral fat stores--were significantly decreased in only a month. This led to beneficial changes in several health indicators, such as increased insulin sensitivity, and better glucose and fatty acid metabolism. Note that the subjects were all type-2 diabetics who have significant defects in glucose and fat metabolism. One wonders what such exercise would do for a person who isn't diabetic. At the least, it would help prevent the onset of diabetes, cardiovascular disease, and even cancer by lowering visceral fat stores.
     Based on the findings of this study, it appears that an increase in GH produced by exercise does indeed offer significant health benefits. In addition, it's clear that GH does promote lower fat stores, at least in the visceral fat stores,even in those with excess bodyfat. We can translate this into explaining the phenomenon of the metabolically fit, yet fat people who regularly exercise, but show no signs of impending disease.

Yamaguchia T, et al.Effect of exercise performed at anaerobic threshold on serum growth hormone and body fat distribution in obese patients with type-2 diabetes.Obes Res Clin Pract 2011;5:e9-e16.

Thursday, January 13, 2011

Which protein is best for appetite control? by Jerry Brainum

For purposes of bodyfat loss, most studies show that low carbohydrate diets provide the most rapid effects. While some critics of low carb diets have said that the initial weight loss seen during low carb diet plans consists of mostly water, more sophisticated body composition tests have shown that on a calorie for calorie basis, low carb diets do promote a greater loss of bodyfat compared to low fat, high carb diets. One reason often stated for the superiority of low carb diets is that such diets modulate insulin release. Insulin is a storage hormone, and has potent effects on promoting bodyfat synthesis, particularly when excess caloric intake is consumed. Since carbs promote the greatest release of insulin, controlling insulin release by consuming less carbs should promote more effective fat loss. But low carb intake is only part of the reason why low carb diets appear to be so effective. Such diets also feature a higher protein intake. This increased protein consumption not only serves to protect vital lean tissue mass, but also provides an increased satiety effect. In other words, it helps to control appetite so you don't overeat.Protein also provides a thermogenic effect, fostering the conversion of fat calories into heat. But which protein sources are best for this purpose?
   This was the focus of a recent study that featured 23 lean, healthy subjects. They consumed four meals, all containing the same amount of calories, but differing in the protein source. The meals consisted of 50% protein, 40% carbohydrate, and 10% fat. The protein sources varied with each meal, with the sources being whey, casein from milk, and soy. A fourth meal used as a control consisted of 95.5% carbohydrate. The results showed that the whey meal provided the greatest thermic effect followed by casein and soy. Fat oxidation after the meal was highest in the whey meal, followed by soy, and was higher in the protein meals compared with the high carb meal. The high protein meals lowered the glycemic response (how high the blood glucose level rose) by 32%, with whey showing the highest insulin release, which accounted for the blunted glycemic response of the meal. Subjective appetite responses from the study subjects indicated that casein and soy proved more satiating than did whey. But the subjects liked the taste of whey more than casein and soy.
     An interesting aspect of this study was the high insulin response produced by the whey meal. Since insulin is blamed for increased fat synthesis, doesn't this mean that whey should promote fat gains? It doesn't work like that. While the high amino acid content of whey, which is rapidly absorbed, does promote an insulin release, it does not result in increased fat synthesis as is the case for processed carbs. But the higher insulin release promoted by whey does blunt appetite, accounting for the increased satiety effect shown by whey. This also explains why large amounts of fructose tend to produce higher bodyfat levels. Fructose doesn't promote an insulin response, so appetite isn't blunted when you consume large amounts of fructose, which in turn tends to promote overeating, and subsequently, increased bodyfat synthesis.

Acheson KJ, et al. Protein choices targeting thermogenesis and metabolism.Am J Clin Nutr 2011: in press.

©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.

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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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