"Ask any of the elite who have become truly massive beasts which anabolic substance has had the most profound effect upon their physique, and the answer from the largest mammals will unanimously be insulin."  That's a quote from Iron Magazine, a publication for body builders. Apparently, injecting insulin for its anabolic properties is not uncommon among the "massive beasts," as several body-building websites actually contain instructions on how to do it and what types of insulin to use.

As unwise as that seems, insulin administration may have a legitimate role in building muscle in the elderly. According to research published in the September issue of Diabetologia, elders suffer from insulin resistance that has nothing to do with glucose metabolism: They have perfect glucose tolerance, but are resistant to insulin's muscle-building actions.

Dr. Elena Volpi of the University of Texas Medical Branch at Galveston and lead author of the study, attribute this kind of insulin resistance to age-related dysfunction of the endothelium, which is the single layer of cells that lines blood vessels. The endothelium controls blood flow by increasing or decreasing the diameter of capillaries (the smallest blood vessels). In younger people, apparently, insulin induces the capillaries to dilate, exposing more muscle to the ingredients necessary for muscle build-up. But even in healthy older people, endothelial dysfunction keeps insulin from having this effect, leading to weakness.

Twice as much insulin as is normally produced by a typical meal, however, works like a charm. As Dr. Volpi noted in a press release, "When we gave seniors double the insulin they would normally produce after eating, their muscles were stimulated like those of young people."

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Sources:

Iron Magazine

Science Daily, from The University of Texas Medical Branch at Galveston