Here’s what experts say about the benefits — and risks — of intermittent fasting

“So, what do you do to eat?”

My annual medical examination was going well and my doctor inquired about my diet. “A bit of everything in moderation? I said, shrugging my shoulders; then, I shot back, “What the hell you to eat?”

“Well,” replied the doctor, “I do intermittent fasting.”

I had heard the hype over the years about how fasting can help maintain a healthy weight and potentially stave off everything from Alzheimer’s disease to sleep apnea to cancer. But it was the sight of my energetic, razor-sharp doctor — who is my age but looks nowhere near him — that made the most compelling case I’ve ever seen for fasting.

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As someone who has never uttered the phrase “I forgot to eat”, who carries granola bars specifically to avoid hunger pangs, I imagined myself as an unlikely candidate for skipping meal. And the information about intermittent fasting seemed so confusing, so contradictory, that I didn’t even know where to start. Do you restrict certain types of food? Do you only eat at certain times of the day? Do you not eat at all on certain days? But above all, I wanted to know: what does it really bring me?

Turns out a lot…maybe.

“Intermittent fasting isn’t about what you eat, it’s about when,” says Elizabeth Ward, a Boston-area dietitian and nutrition consultant. “With no calorie restrictions or special foods to prepare or purchase, IF (intermittent fasting) is more of a lifestyle than a normative diet.”

How you go about it, however, can be flexible.

“There are several types of IF, including time-restricted eating and not eating or eating very little food for entire days,” Ward continues. “On the 16:8 plan, only calorie-free drinks are allowed for 16 hours and you eat for an eight-hour period of your choosing. The 5:2 plan involves eating as usual five days a week and consuming 25% of your daily calories (about 500 for women and 600 for men) on other days Alternate Day Fasting (ADF) means drinking calorie-free beverages every other day of the week and eating on the remaining days.

Most people find out about IF because they are interested in losing or maintaining weight, as it seems to promise dramatic and fast results. It’s definitely a simple way to limit calories and avoid foods that are less nutrient dense.

“Breakfast in the United States is generally a high-carb, high-sugar, high-calorie meal,” says New York physician James Stulman, a physician in my local practice. “And then after 7 p.m. it’s a really tough time. A lot of my patients, myself included, are hungry by 9:30 p.m. We’re snacking on cookies or something sweet. So if you’re disciplined enough not to eat after seven hours, you’re probably getting rid of all the bad carbs, which are the real problem.”

But unlike other diets, intermittent fasting seems to offer real possible health benefits because it triggers different processes that can make the body more efficient. A 2021 article in the journal Nutrients explains, “Following periods of restricted food intake, the human body initiates a metabolic shift from glucose to stored lipids, leading to a cascade of associated metabolic, cellular and circadian changes. many health benefits in animal models and humans. Periods of FI have not only been associated with weight- and metabolism-related diseases, but also with reduced risk/prevalence of neurological diseases.

And a widely circulated review from the New England Journal of Medicine in 2019 on the “Effects of Intermittent Fasting on Health, Aging, and Disease” reported that “The metabolic shift from glucose-based energy to energy-based on the ketone” may result in “increased resistance to stress, increased longevity and decreased incidence of diseases, including cancer and obesity.”

There is science that attests to why intermittent fasting can be healthy for your cells. Christine Kingsley, director of health and wellness at the Lung Institute and advanced practice registered nurse, explains that “during intermittent fasting, the body reaches lower glucose levels more efficiently, catalyzing the activation of synapses and resistance to stress. This allows the brain to function at its full humanly possible capacity, which is why verbal memory is significantly improved during and after practice.”

There are also other potential benefits.

“One of the main effects is a reduction in insulin levels,” explains John Landry, Registered Respiratory Therapist and Founder and CEO of Respiratory Therapy Zone. “HHigh insulin levels have been linked to an increased risk of chronic diseases like diabetes and heart disease. By reducing insulin levels through intermittent fasting, individuals may be able to reduce their risk of these conditions. Intermittent fasting has also been linked to lower inflammation, which is thought to be a contributing factor to several chronic diseases.” He adds, “There is currently little research on the effects of intermittent fasting on lung health. However, some studies suggest that intermittent fasting may have potential benefits for respiratory function, such as reduced inflammation and improved oxidative stress.”

Intermittent fasting also means your body isn’t busy digesting during your off hours. It can lead to better sleep, experts say.

“An IF schedule that schedules your last meal at least two to three hours before you go to bed (caution: for the general population, not for night shift workers) can support healthy sleep and optimal daily energy by several ways,” says Chester Wu, a board-certified physician in psychiatry and sleep medicine with the RISE sleep and energy app. “It allows for better digestion, reducing the risk of heartburn and acid reflux that keeps you up at night.” Plus, he says, “when we sleep, our brain eliminates waste. But if your body is busy digesting a meal, blood is diverted to the digestive system, leaving the brain with fewer resources to do that job.”

Regardless of the perceived benefits of SI, some people absolutely shouldn’t try it. As Elizabeth Ward explains, this includes “persons under 18 and over 75; pregnant and breastfeeding women; those taking medications that must be taken with food at certain times of the day; those with a chronic illness, such as kidney disease; people with a history of eating disorders.” She adds: “IS can be a trigger. Preoccupation with when to eat can encourage obsessive behaviors regarding food. Additionally, exercise lowers glucose and insulin levels, and people who are SI-dependent may need to modify the intensity and timing of exercise to prevent fatigue.”

I may be intrigued by intermittent fasting, but my current lifestyle isn’t really compatible with it. I could get by with just black coffee for breakfast, but I’m not ready for ever-early dinners just yet. People who have families, who travel or socialize, or who have irregular schedules would likely also have difficulty staying on intermittent fasting. And any diet is only as good as your ability to stick to it. So for now, I will continue to pay more attention to what I eat than when. “First and foremost the most important,” says Dr. Stulman, “is your food choices.”