Here’s how intermittent fasting can be safe and effective

By Kathleen O'Brien, for MDLinx
Published January 8, 2019

Key Takeaways

Are you intrigued about intermittent fasting enough to pencil it onto your list of New Year's resolutions, but worried about how to do it in a healthy manner?

Intermittent fasting restricts caloric intake for a set number of hours or days, and focuses on when you eat instead of what you eat, or how much. One popular version recommends fasting for 2 non-consecutive days each week. Another suggests alternate days of fasting. Others prescribe so-called “time-restricted” feeding or limiting eating to a daily block of time lasting anywhere from 8 to 12 hours.

At the 2018 annual conference of the European Society of Endocrinology, Brazilian scientists reported that while lab rats lost weight after a 90-day regimen of alternate-day fasting, they gained stomach fat and lost muscle. Even worse, these researchers found that pancreatic changes hinted at an increased diabetes risk.

In light of these results, can any intermittent fasting regimen be undertaken safely?

Absolutely, said Monique Tello, MD, MPH, FACP, author of  the newly published “Healthy Habits for Your Heart.” Dr. Tello, internal medicine physician, Massachusetts General Hospital, and clinical instructor, Harvard Medical School, Boston, MA, also contributes to the Harvard Health Blog, where she has written about intermittent fasting.

Dr. Tello noted that the results coming out of the 2018 conference held in Barcelona were presented in a poster. Furthermore, very few details are readily available, and the conclusion goes against many studies done in humans.

“It sounds very provocative and interesting, but we would probably need to see it done again, and explained, and then published,” she said. “So, it's several steps away from being taken seriously. There's so much more (research) that really overshadows what these [researchers] are saying.”

Although Dr. Tello remains convinced intermittent fasting is a good choice for people who already eat a healthy diet but still can't lose weight, she cautioned that it isn't for everyone.

“People who are already on diabetes medications (pills or insulin) shouldn't fast without the supervision of their doctor, because the risk of dangerously low blood sugars is real. If they take their meds and then don't eat, they can become hypoglycemic.”

The other kind of patient who should approach intermittent fasting warily is someone with a history of anorexia, bulimia, or binge eating.

“Intermittent fasting could be triggering and put people who were in remission back in a harmful eating pattern,” added Dr. Tello.

Binge eaters, in particular, may feel justified gorging on food during their non-fasting time slots.

“Fasting does not allow feasting,” she noted. “When you eat, just be eating a normal amount of healthy foods.”

In healthy people, whether they are of normal weight, overweight, or obese, “there is little evidence that intermittent fasting regimens are harmful physically or mentally (ie, in terms of mood),” according to a review of fasting studies done out of Moores UCSD Cancer Center, University of California, San Diego, La Jolla, CA.

Furthermore, of the 13 intermittent fasting trials that were reviewed, 11 were found to have produced weight loss results in trial subjects.

One drawback, of course, is the burden of hunger that will occur during any full day of fasting. For that reason, the more hardcore fasting regimens are the hardest to maintain.

Dr. Tello's advice to patients who want to try some form of structured fasting is to start with a healthy Mediterranean, plant-based diet. Get rid of any over-reliance on red meat or processed carbohydrates first.

Next, cut out snacking as much as possible.

“Give your body time to stop digesting your previous meal before embarking on your next meal. Otherwise, your body never taps into the energy stored in your fat cells,” she said. “I tell people, 'Just eat three meals a day.' People look at me like I'm nuts.”

The final step is to extend the number of hours during which you fast by ditching any late-night snacks and postponing breakfast. That lengthens by several hours the fasting that occurs naturally during sleep.

“I just sort of stumbled into this pattern myself, and it works. And now I know why,” she said. Have coffee or tea in the morning, get busy with work, then eat the day's first meal several hours later than a traditional breakfast. After dinner, the kitchen is closed; no late-night snacks.

“That's really doable for many people,” she said. “For physicians who are busy, this works great.”

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