Remember when the quintessential big screen body transformation belonged to Robert DeNiro in Raging Bull? These days, it seems like any actor worth his weight in awards statuette gold commits to a role that requires an extreme physical makeover. For some, it's about look-at-my-muscles machismo, while others go for ego-shedding emaciation, or full-on fatness.
The good news for these guys is that studies have shown that weight cycling – aka yo-yo dieting – doesn't necessarily alter a person's body composition over time. But the bad news is that it can damage blood vessels and increase a person's risk of a heart attack. So does that mean a one-time weight shift for a role is less dangerous than making a career of it? "It's not healthy to artificially manipulate your body in this way, says Linda Bacon, author of Health at Every Size: The Surprising Truth About Your Weight. "The more you do it, the more problematic it is."
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For anyone who has an underlying history (or even just an inherited risk) of medical conditions such as diabetes or high blood pressure, gaining a significant amount of weight for a role – even if it's only temporary – can be a dangerous pursuit, says Dr. Robert F. Kushner, clinical director at the Northwestern Comprehensive Center on Obesity. Even without any predispositions, these guys are still putting themselves at risk for those medical conditions, not to mention high cholesterol or a fatty liver. And don't forget the cosmetic effects of gaining weight quickly: stretch marks.
Extreme weight loss, on the other hand, can result in low blood pressure and blood sugar, dehydration, decreased muscle mass, and compromised immunity. (One study found that moderate weight loss can affect a person's immunity, while another study concluded that high-intensity endurance exercise also can increase a person's chances of getting sick. A depletion of vitamins, minerals, and even carbs are to blame).
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Regardless of the direction the scale moves, Kushner says, "I would be shocked if these actors don't have someone with medical training or fitness training or nutritional training who is watching them very closely." Take a look at some of Hollywood's biggest shape-shifters, from those who tried it once, to the repeat offenders.