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Before he faces off against undefeated boxer Floyd Mayweather, UFC champion Conor McGregor must conquer the scale.

And that could prove an even more dangerous opponent.


In pre-fight trash talk, Mayweather has claimed that McGregor looks “extremely heavy” and has been scrambling to try to drop 10 pounds. (Both fighters have to come in under 154 pounds at the weigh-in on Friday afternoon if their much-hyped bout is to proceed.)

The truth is, though, shedding 10 pounds in a couple days is no big deal for most MMA fighters. In the past, McGregor has reportedly cut more than 25 pounds in eight days’ time.

The key question is whether they can do it without damaging their health. And even the nutritionist charged with guiding McGregor to his fighting weight said that’s a difficult balance.


“It’s nothing I’d recommend to everyday people,” George Lockhart, the nutritionist, told STAT in an interview. “I always tell people if health was your number one priority, MMA is not the sport you should be going into.”

MMA fighters are known to dehydrate themselves — using everything from saunas to sweat suits, hot baths to water pills — to shed up to dozens of pounds in the days ahead of a weigh-in. After making weight, they try to quickly regain it by eating food and drinking water in hopes of gaining the competitive advantage of size over their opponent.

Lockhart, a former fighter and Marine veteran, generally starts on the Tuesday before a weigh-in. He removes sodium from a fighter’s diet and offers herbal diuretics that include potassium to replenish lost nutrients. He’ll also have a fighter taper water consumption over several days — two gallons on Tuesday, one gallon on Wednesday, occasional sips when thirsty on Thursday. The day before the weigh in, Lockhart takes carbohydrates out of fighter’s diet and “cleans out” his or her intestinal tract. On that final night, fighters sometimes work out or take a hot bath. He monitors vitals, including body temperature and blood pressure, throughout the process.

“Ten pounds in four days is like a hiccup,” Lockhart said. “What Floyd’s talking about, it just shows he’s probably never cut weight before.”

But dropping weight that fast — even “just” 10 pounds — draws concerns from doctors. Dr. Larry Lovelace, a ringside physician in California, told STAT several fighters have died over the past few years from the practice, which athletic officials have called “the biggest problem in the sport” today.

A 2013 study in the Journal of Strength and Conditioning Research found that 39 percent of MMA fighters studied experienced “significant or serious dehydration” before their fights. Lovelace said the body doesn’t fully rehydrate for at least two days — well after a fight ends. That means fighters could experience muscle cramps and loss in agility while in the ring, he said.

“It only takes 2 percent dehydration to impair your performance,” Lovelace said. “There’s no way they’re going to recover, and it’s definitely going to affect their performance.”

There are bigger health risks, too. They include:

The brain: When a fighter takes a punch to the head, the brain rattles off the front and the back of the skull. That’s not healthy in the best of conditions. Dehydration makes it worse. “The brain is bathed in fluid,” said Dr. Edmund Ayoub, vice president of the Association of Ringside Physicians. “Without that fluid, the brain has less cushion.” Therefore, the risk of injury could be greater for a fighter who spars during the process of weight cutting. “The brain can hit harder against the skull,” Ayoub said. “You may have more [risk for] brain injury.”

The heart: A fighter’s heart beats faster than normal when dehydrated. “If you normally walk around with a resting heart rate of 72, now it may be 90 or 100,” Lovelace said. “So going into a cage to fight, there are potential cardiac risks.”

In a 2013 interview with Vice Sports, ringside physician Dr. Michael Kelly said dehydration can impact how the body regulates sodium and potassium levels and, in turn, mess with the cardiac fibers conducting electricity inside the heart. “So if those signals aren’t propagating along the channel correctly,” Kelly said, “the heart can go into an irregular heartbeat or fatal heart rhythm and wind up in cardiac arrest.”

The kidneys: Nephrons, the tiny structures inside the kidney that produce urine to remove waste from the body, malfunction without enough water.“Your kidneys literally dry up,” Ayoub said. “When kidneys get dried up, you can get kidney damage.” In 2015, fighter Johny Hendricks had to be rushed to the emergency room after weight cutting led to intestinal blockage and a kidney stone. Doctors say they’re also at risk of sustaining chronic kidney issues due to the practice.

Ayoub thinks fighters would remain healthy if they made sure to lose no more than 2 percent of their body weight each week. If McGregor had to lose 10 pounds, for instance, he should aim to shed it over three weeks instead of just one, Ayoub said.

Lovelace, though, said there is “nothing to be gained” from the practice of weight cutting, in part because both fighters are often doing the same thing, canceling out any potential advantage from packing on pounds immediately after the weigh-in.

Lockhart, for his part, believes fighters will keep cutting weight no matter what. So he considers it his job to help them do it as safely as possible. “There’s no degree for weight cutting,” Lockhart said. “You need people to show them how to do it in the proper way.”

MMA writer Iain Kidd, who has observed Lockhart’s training methods for a forthcoming book, puts it this way: “There are ways to do it safer — but not ways to do it safely.”

  • This “fight” will be over Saturday. It is the most egregiously over hyped, advertised and boring in the history of fights. I am so sick of it, and here we are on a medical website and you are making it worse. I don’t like a “sport” that champions 2 people who are trying to kill each other with their hands/body. They will apparently both make a lot of money, >100 million. Jesus wept!

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