C.J. Hunter, the ex-husband of champion sprinter Marion Jones, is alleging that Jones used performance-enhancing drugs during the 2000 Olympics in Sydney, Australia. Hunter, a retired shot putter, says his then-wife relied on a cornucopia of banned substances, including human growth hormone, the steroid THG, the endurance booster EPO, and insulin. How is an athlete's performance aided by insulin, a substance more commonly used by diabetics to control their blood sugar?
Chiefly by boosting the body's supply of glycogen, a crucial muscle fuel. As diabetics know well, insulin, which is produced naturally by the pancreas, is a hormone that regulates blood-sugar levels by enabling the breakdown of glucose. The hormone stimulates this process (called glycolysis) by transporting glucose into muscle cells, where it is metabolized. If the muscles are flooded with too much glucose at once, however, they store the excess in the form of glycogen, a complex carbohydrate that provides energy to muscles during physical exertion. The more glycogen an athlete possesses, the longer she can keep her muscles pumping.
Insulin is thus popular among endurance athletes, such as cyclists. But in combination with anabolic steroids, glycogen is also effective at maintaining muscular bulk. The substance plays a key role in inhibiting protein breakdown; that's why, when bodies are starved of insulin (and, as a result, glycogen), they tend to quickly metabolize muscle proteins in order to gain energy. So bodybuilders, powerlifters, and other athletes concerned with sheer mass like to use insulin as a way to preserve the muscular gains they've made with steroids.
The hazards of insulin abuse are well-documented. An overdose can cause the body to break down far too much glucose, leading to dangerously low blood-sugar levels. The consequences of this condition, known as hypoglycemia, can range from nausea to death. Last December, for example, a former Miss Universe contestant from Scotland, Louise Nuttall-Halliwell, died after spending nearly two years in an insulin-induced coma.
Theoretically, at least, it shouldn't be difficult to test for the presence of illicitly consumed insulin, as the injectable variety—which is either genetically engineered or taken from animals—differs chemically from the stuff manufactured by the human pancreas. Unfortunately, insulin also passes through the body rather quickly—usually within an hour—and so post-competition tests have almost zero chance of catching a miscreant red-handed.
Bonus Explainer: Insulin has been on the International Olympic Committee's list of banned substances since 1998. But the IOC makes exceptions for athletes who can prove that they genuinely suffer from diabetes—good news for American swimmer Gary Hall Jr. A four-time Olympic gold medalist who was diagnosed with Type-1 diabetes in 1999, Hall recently qualified for his third Olympic team.