The amino acid L-Arginine continues to be popular with bodybuilders who believe it stimulates growth hormone secretion. Among other functions growth hormone (GH) has anabolic effects in muscle while promoting fat loss. Although arginine is sold as an oral supplement, few
bodybuilders realize that the research documenting its GH-releasing actions involved intravenous administration.
When consumed orally, arginine travels through the portal vein to the liver, but a liver enzyme called arginase degrades most ingested arginine, thus preventing an elevated blood arginine level. A frequently quoted 1981 Italian study showed that a combination of 1,200 milligrams of
arginine and the same amount of another amino acid, lysine, resulted in a sevenfold increase in GH-I secretion among the subjects.
Even so, the success achieved by this study has never been replicated. Other studies did indicate favorable changes in body composition after arginine supplementation, but none measured actual GH output. Based on the equivocal findings concerning arginine and GH release, researchers
from the Virginia Polytechnic Institute tested the effects of the amino acid on 18 weight-trained men who were divided into three groups: 1) arginine users, 2) a control group of subjects who used no arginine and 3) a placebo group who were given an inactive substance. Each group
consisted of six men, all of whom trained at similar intensity levels.
While the control group followed no particular diet, both the arginine and placebo groups used a low-calorie diet for 10 days. Both groups lost weight and bodyfat during the low-calorie phase and showed increased strength in biceps and thigh exercises. None of the groups, however,
showed elevations in GH or differences in nitrogen retention indicative of an increased anabolic effect.
Measurement of insulin-like growth factor I (IGF-l) showed no changes, which also pointed to arginine's lack of effect on GH status, These results led the researchers to conclude that oral arginine is an ineffective supplement for promoting GH release.
Future Obesity Treatment
As noted, growth hormone has lipolytic, or fat- burning, effects, but it also does several other things in the body, such as excessively stimulating the growth of certain bones. What if you could isolate the fat-metabolizing effects of GH? Australian scientists believe they have done
just that. In a study reported in the August '94 issue of the medical journal Biochemistry and Molecular Biology International, the Aussie scientists isolated a section of GH that reduces body- fat up to 25 percent in lab rats. This GH derivative accelerates body-fat degradation
while inhibiting fat retention in the body.
One of the researchers, Frank Ng of the Department of Biochemistry at Monash University in Melbourne, said he still thinks that most people should continue to rely on more conservative methods of fat loss, such as diet and exercise. He notes that the molecular form of the substance,
called synthetic HGH 177-191 peptide, isn't chemically stable enough to be produced in pill form.
What's the Minimum Healthy Level of Bodyfat?
A good average level of bodyfat in a man is about 15 percent. The figure is higher for women because of an additional type of far called sex-specific fat found in breasts, hips and upper thighs. A competitive bodybuilder with a bodyfat level of 15 percent would appear smooth,
especially considering the current standards of muscular definition that win contests.
While most champion bodybuilders aren't aware of their precise bodyfat levels, most have a general idea. Others are unconcerned with figures, preferring to let the mirror determine the success of their training, dieting-and in some cases-drug regimens. Still, you occasionally read
about bodybuilders and other athletes claiming bodyfat levels as low as 1 percent. What makes such claims suspicious is that males carry 3 percent of their bodyfat in a form called essential fat. As the name implies, the body doesn't like to tap into this particular fat, since it
supports essential functions. One example is the fat that surrounds internal organs, such as the kidneys. Other tissues containing essential include nerve sheaths and cell membranes.
Fat surrounding the eye socket maintains eye stability while fat stores in both feet and hands provide important padding. As mentioned above, the body is loath to tap into this essential fat. In animals whose blubber-that is, fat-is essential to survival, such as elephant seals and
king penguins, the body will break down its own muscle, or protein, rather than use fat stores during energy deficits.
So the question remains, What's the minimal amount of healthy bodyfat in a man? Testing a newer, high-tech technique called dual-energy X-ray absorptiometry, United States Army researchers sought an answer to this question. After testing various Army subjects, the researchers
concluded that 4 to 6 percent bodyfat was the minimal healthy level achievable in men. They also observed that a male starting out at 15 percent bodyfat who loses 16 percent of his bodyweight will have a virtual depletion of available fat stores, with the exception of essential fat.
An important point to consider is that any toss beyond this percentage consists of lean tissue such as muscle-not fat.