Fasting for weight loss? Here’s why scientists say it works long-term | Globalnews.ca (2024)

For the past 12 years, Dr. Steve Mount hasn’t eaten on Tuesdays, Thursdays and Saturdays. Those days are earmarked for fasting.

In 2004, he read a study about how intermittent fasting, at least in mice, led to a longer life. The research was compelling enough to give it a try. The University of Maryland geneticist says he was slightly overweight at about 180 pounds. Within six weeks, he lost 10 pounds off of his 5’11″ frame.

“What led me to take it up was that it was doable. What kept me doing it was the response — it did improve my stability, my ability to remain focused throughout the day, my insulin response,” he told Global News.

“It’s not a crash diet. It’s something that’s sustainable.”

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Intermittent fasting, which calls for 12 to 24 hours of skipping meals, used to draw controversy because it seemed extreme. But scientists who study fasting say it’s now widely accepted as a weight loss and weight maintenance tool that works in the short-term and as a lifelong lifestyle.

Dr. Krista Varady remembers presenting her research on fasting a decade ago. While the University of Illinois at Chicago professor’s results showed fasting was promising, they weren’t well received.

“Doctors and dietitians used to be very against this diet and I’d present and people would have a lot of problems with it. They thought about safety issues, the drop on metabolic rate, and the effect on eating disorders,” she explained.

Tweet ThisClick to share quote on Twitter: "Doctors and dietitians used to be very against this diet and I'd present and people would have a lot of problems with it. They thought about safety issues, the drop on metabolic rate, and the effect on eating disorders," she explained.

Fasting is undergoing a renaissance, though.

“People are gaining a lot more confidence in it because the science is behind it. It’s working and it’s not harming people in any way. Clinicians are way more positive about it,” Varady told Global News.

Tweet ThisClick to share quote on Twitter: "People are gaining a lot more confidence in it because the science is behind it. It's working and it's not harming people in any way. Clinicians are way more positive about it," Varady told Global News.

Her over-decade-long tenure in academia has put alternate day fasting — she calls it Every Other DayDiet— to the test in many ways.

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In short-term studies, she learned that those who fast for a day don’t binge the next day at all. At most, they’d eat about 10 to 15 per cent more calories once they broke their day-long fasts. Despite a slight increase, the calorie reduction was still enough to see weight loss.

In other trials, volunteers had lower LDL cholesterol and triglyceride levels, their blood pressure and insulin levels improved, and they gained protection against heart disease and diabetes risk.

Journalists wondered if volunteers had energy to work out. In 12 week studies, those fasting were tasked with exercising whenever they wanted three times a week — turns out, many chose to exercise on their fast days over their feast days.

“It didn’t matter because people felt this boost of energy. They didn’t have a problem with exercising,” Varady explained.

READ MORE: Follow this one tip if you’re trying to lose weight, study suggests

(On her fasting methodology, patients are allowed to eat one 500-calorie meal a day. If exercise is worked into the equation, Varady recommended saving the meal for a post-workout refuelling. The ideal meal is two chicken breasts — about 50 to 70 grams of protein — on a bed of salad and vegetables because it’s rich in protein, fibre and nutrients, she advised.)

Alternate day fasting was within reach for obese volunteers, too. All groups had difficulty with irritability and hunger pangs during the first few tries, but those feelings dissipated within 1.5 weeks, she said.

It didn’t matter if volunteers were on high-fat orlow-fat diets, too. Another study of hers revealed that those on a high-fat diet cheated less and lost a bit more weight than their low-fat counterparts.

How much people lose on an intermittent fast depends on their height and weight. Varady says it’s about one to three pounds of weight loss, while those who weigh more lose up to five pounds.

READ MORE: Will the Paleo diet make you fat? Why this controversial study is angering diehard supporters

Brad Pilon, the Canadian author of Eat Stop Eat, says weight loss is about 0.5 pounds of true body fat. Initial weight loss may seem steep because of water weight.

“On a day you don’t eat for 24 hours, you’re guaranteed to be losing a third or half a pound of non-water weight that’s mostly from body fat,” Pilon told Global News.

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“The truth is intermittent fasting is a way to create slow, steady weight loss.”

Tweet ThisClick to share quote on Twitter: "On a day you don't eat for 24 hours, you're guaranteed to be losing a third or half a pound of non-water weight that's mostly from body fat," Pilon told Global News.</p><p>"The truth is intermittent fasting is a way to create slow, steady weight loss."

Varady said her findings point to people losing up to 90 per cent of fat from fasting while people who reduce calories and slowly lose weight shed about 75 per cent of body fat.

In Pilon’s fasting model, dieters don’t go cold turkey for an entire day if it doesn’t fit their schedule. Instead, they can start after any meal, and aim for anywhere between 12 to 24 hours. Pilon fasts at least once a week and it’s helped him lose 20 pounds and maintain the same weight he had in his university days — a lean 175 pounds, he said.

READ MORE: 9 diet and weight loss mistakes you’re making

Your body runs off of burning food you just ate as fuel but once that food is tapped out, it’ll turn to your fat reserves, Pilon explained.

“The whole purpose of body fat is to be able to burn it when food supply is scarce,” he said.

Fasting has deep roots in evolution, religion and in plenty of cultures that relied on its health benefits for centuries, according to Dr. Mark Mattson, chief of the U.S. National Institute on Aging.

“The way we eat now is built around three large meals a day plus snacks…but we’re geared genetically for going extended periods of time without food and functioning well. If our brains and bodies didn’t function well we wouldn’t have survived,” Mattson said.

He’s been studying fasting since 1996. He hasn’t had breakfast in 35 years and takes up skipping a meal nearly daily in his fasting routine.

“There’s more than one physiological effect on fasting that seems to be good for health,” Mattson told Global News.

In his research on mice, he found that having them fast every other day extended their life expectancy by 30 per cent.

READ MORE:6 misconceptions about nutrition and healthy eating

When Mattson toyed with factors, such as memory loss and heart health, the mice who were on fasting regimes were much more resilient in staving off disease.

In preliminary findings Mattson is combing through now, he found that fasting rodents that had cancer and were on chemotherapy garnered better results in killing cancer cells compared to their peers.

Varady’s findings in mice found that fasting reduced cancer risk overall, too.

The good news for those trying to lose weight is fasting – if incorporated into your lifestyle regularly – doesn’t equate to yo-yo dieting, Varady says.

In a year-long study, she had dieters on alternate day fasting lose nine per cent of their body weight over six months. In the subsequent half of the trial, the group maintained their new weight.

The experts promise fasting is feasible, too. For Pilon, a 24-hour timeframe is easier to adhere to rather than a months-long attempt at logging meals in a food diary and counting calories.

“Once you’re done it, you’re done. It’s a positive reinforcement so it’s a different approach to calorie restriction,” Pilon said.

“Psychologically, it’s easier to focus on a few days a week than having to worry about counting calories at every meal,” Mattson said.

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Tips: If you’re thinking of taking up intermittent fasting, the experts have these tips:

Drink eight to 12 glasses of water: A majority of our water sources comes from food, so on fast days, load up on water, Varady says. If you’re dealing with headaches or migraines, it could be from lack of hydration. Tea and black coffee are safe bets on fast days.

Pick a busy day: If you’re sitting at home with nothing to do, you’ll have food on your mind the entire day, Pilon says. Choose a day where you’ll be social or have projects on the go so you may be too busy to clue in that you’ve missed a meal.

Your feast days shouldn’t be treat days: Pilon breaks has fasts by going back to his regular routine — he grabs Tim Hortons, he’ll have a sandwich for lunch and dinner with his family. Your non-fasting days shouldn’t be cheat days where you overindulge on junk food.

Don’t fast if you’re dealing with other health issues: Varady says fasting isn’t a good idea if you have a history of binge eating, or other eating disorders. If you’re pregnant, diabetic or have low blood pressure, you should consult with your doctor before considering a fast, too.

carmen.chai@globalnews.ca
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