How much weight can you lose during a water fast

On the night of September 30, Hayley Ryczek and her husband went out to one of their favorite restaurants, where Ryczek sunk her teeth into a sizzling ribeye steak. When she came to the last bite, she savored it; it would be the last she would eat for a month.

The next day, Ryczek, a cookbook author and lifestyle blogger who lives near Pittsburgh, would embark on a 31-day “water fast,” during which she would consume only water, tea, seltzer, lemon juice, vitamin pills, and occasionally broth.

On the first day, she went on a six-mile hike, and the next, she prepared a spread of food for a church party. “Pretty much all day I wasn’t tempted to eat,” she wrote, “only dying for a big glass of sangria!” (She resisted; booze wasn’t part of the plan.)

If Ryczek was going to diet, she would go all the way. “I’m one of those people who set their sights on the best of the best,” she told me recently. “If you lift weights, you want to lift the most you can. I was ready to clean some things up, get a fresh start, always on a journey … Why not just do it?”

She is part of a small—yet surprisingly vocal—community of health fanatics who purport to have given up food for a month at a time or more. Weight loss, if accomplished, is often underplayed, as though it’s a mere fringe benefit to the enlightenment that self-imposed starvation provides.

Some, following Jesus’s example from the Bible, fast for 40 days for spiritual growth—and some have died trying. Others crave a vague “detox” or “reset” of their bodily systems. One graduate student fasted for a month in order to “clean” her insides and get “a fresh start with everything.” Some combine all of these motivations into a hodge-podge, depriving and actualizing the self all at once: “The 40 day fasting diet was like a ‘reset button’ in my life,” one faster wrote. “Isn’t [it] great that God in His wisdom has provided us with this tool to engage in a more intimate way of life with Him, while at the same time restoring health to our bodies and minds!”

Successful fasters post their own guides online, doling out wisdom like, “If you ever feel dizzy during your fast, try to sit down as quickly as possible.” One woman, who drank only juice for 31 days, dismissed her headaches as “healing reactions.” Ryczek is personally inspired by the work of Jason Fung, a Canadian nephrologist and the author of The Complete Guide to Fasting. Over email, Fung told me there is “nothing wrong” with fasts of up to a month. “The key to longer fasts is that you should feel well throughout the time,” he said. “If you feel weak or tired, then you should stop.”

The exact numbers of these marathon fasters are unknown. Certainly not all who try it post about it online, because the scorn can be overwhelming. Ryczek said she received death threats after her post was shared on a “lynch mob, troll Facebook group.”

“They were a pro-GMO, pro-vaccine group that came at me and attacked,” she said. “They said I’m a liar and if I’m not already dead from my lie, someone should kill me.”

For those who wonder if Ryczek must have cheated: It’s technically possible to survive more than a month without food, though the likelihood you’ll live depends on your level of fat—and thus, the amount of energy your body can burn before it starts eating itself. The longest known fast was in 1971, when a 27-year-old man survived on water and supplements for 382 days and shrank from 456 to 180 pounds. In 1981, Irish republican prisoners refused food for more than two months before dying, but in 2010, a Florida woman on a water-only religious fast died within just 26 days. (The precise length of her fast wasn’t clear. When her family members broke down her door, she was already gone.)

Ryczek is propelled not by a cause but by an iron will. She’s fasted for shorter periods previously, even sitting through big holiday dinners without so much as a nibble.

For the first few days of the monthlong fast, she was irritable, finding herself “wishing (even more than usual) that Ray [her husband] would just stop freaking talking,” she wrote, adding, “I’m starting to realize that my defense mechanism against feeling has been turning to food/drink. I’m grateful to be on this path, giving me the opportunity over the next 22 days to break that vicious cycle, no matter how much I cry.”

Still, she claims her energy never flagged. She had so much, in fact, that she cooked for her husband and remodeled her kitchen. (“When you fast, as your body gets away from digestion, it has so much more energy to do other things,” she told me.) Though occasionally she would sense an empty pang in the pit of her gut, most days she didn’t feel hungry.

Other faster-bloggers similarly claimed they worked long hours almost every day of the fast. (“90 percent of eating is EMOTIONAL,” one person wrote, in bold.)

Even if these fasts are technically possible, though, medical experts don’t recommend fasts of more than a day or two. Most people, including overweight people, lose some muscle mass with every pound they shed. Without glucose going to the brain, thinking becomes more difficult. Blood pressure drops, and you risk passing out.

“In the absence of getting protein and glucose from the food that you eat, you start to cannibalize the body’s protein,” explains Thomas Wadden, the director of the Center for Weight and Eating Disorders at the University of Pennsylvania. After using up the liver’s glycogen stores, the body comes for the glucose in the muscles. “You end up eating up the body’s muscle tissue,” Wadden says.

This includes the heart, which, after all, is just a large muscle. Eventually, the heart may slip out of rhythm. If the heart doesn’t fail before the fast ends, heart troubles can persist after the person starts eating again.

Decades ago, doctors tried treating obese patients with fasting, but they stopped after five patients died, two from heart problems. In the 1970s, nearly 60 people died after spending an average of four months on a fad liquid protein diet. People with severe anorexia most commonly die of heart disorders.

Ryczek, who was about a size 10 when she began her fast, didn’t worry about the health impacts. In an effort to balance her electrolytes, she drank Himalayan sea-salt water.

Prolonged fasting is also not as effective a weight-loss strategy as it may seem, experts told me. Though intermittent fasting—in which people consume little or nothing for up to 24 hours at a time—has been shown to help some people lose weight, the same is not true of long-term fasts.

“One of the big-picture ideas behind intermittent fasting is called hormesis,” said Grant M. Tinsley, a Texas Tech University professor of exercise physiology who has studied intermittent fasting, via email. “Hormesis refers to an exposure to a relatively small amount of some stressor, which could cause the body to adapt and become more able to deal with other stressors. This is in contrast to exposure to a large stressor, which could cause harm to the body. In my opinion, short-term fasts, such as those used during intermittent fasting, would fall into the category of the small stressors which could promote health benefits. However, long-term fasts could potentially fall into the ‘large stressor’ category.”

Reducing food intake for weeks causes metabolism to slow, so that a person who once needed 2,000 calories per day to function might now need only 1,800. After the fast is over, it’s not clear whether the metabolism will bounce back. A recent study of contestants on The Biggest Loser, who cut their calorie intakes dramatically for the show, found the participants must now eat hundreds fewer calories each day than people of a similar size in order to maintain their reduced weights.

The other reason extreme dieting was discontinued as a treatment for obese people was that the majority regained most of their weight shortly after the treatment. In a 1994 study conducted by Wadden, people on a “very low-calorie diet” of 420 calories per day lost more of their starting weights than people on a more reasonable diet of 1,200 calories a day. But the “very low-calorie” group regained much of their weight within the next year, ending up heavier than the group that didn’t starve themselves.

Another case for prolonged fasting that Ryczek and others have cited is that it’s supposedly our natural state. It was common, the thinking goes, for ancient humans to go months without food. Even if they did, “that doesn't mean that starvation per se is good for us,” said Marlene Zuk, a professor of ecology and evolution at the University of Minnesota, via email. “The body is remarkably flexible in what it can deal with, but it doesn’t necessarily follow that dealing with a particular challenge makes us stronger.”

Finally, Alan Aragon, a nutrition researcher, cautions that fasting can set the stage for eating disorders such as anorexia and bulimia. “Any way you slice it,” he says, “it’s a bad idea.”

Wadden suspects people undertake long fasts because they “can feel very virtuous by giving up eating for a while.” But, he concludes, “there’s nothing beneficial about total fasting. You’re living in a physical body that does have nutritional needs.”

The end of the fast can be the most hazardous part. Reintroducing food into the body can shift electrolytes and fluids in a way that strains the organs. Despite careful re-feeding in a hospital, the performance artist David Blaine suffered abnormally low phosphate levels when he began taking in nutrients again after emerging from a glass box in which he had been fasting for 44 days in 2003.

Ryczek was never tempted to break her fast, though she did fantasize about the meal she would eat to conclude it. On October 31st, the day had come. She made herself a roasted butternut squash puree, venison chops, green beans, and some mushrooms. (“Amazing!!” she proclaimed.)

In all, she had lost 24 pounds. It’s was just the beginning, though: Next year, she plans to do another fast, this one 40 days long.

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