What You Need to Know About Intermittent Fasting

Some fans of this trendy eating plan report weight loss and increased energy — all without counting calories. Here’s what happened when I tried it.

By
Published December 27, 2019
Getty Images

What do Halle Berry, 53, and TV host Terry Crews, 51, have in common? Beyond good looks and big bank accounts, both reportedly manage their weight by intermittent fasting (IF). That means cycling between periods of eating and periods of fasting, which can range from 12 hours with no food to two days (yikes!) per week of eating fewer than 500 calories.

The 16/8 method, however, is one of the most popular. Followers of this method fast for 16 hours. For many people, that means skipping breakfast, then consuming all their meals between an eight-hour window, say between 1 and 9 p.m.

Fitness influencer Janielle Wright, 29, has used various timeframes and credits IF, plus a low-carb diet and six days per week of exercise, with her losing more than 100 pounds. She details her holistic wellness journey from 337 pounds to less than 237 pounds within a year on social media. Wright stresses the importance of thoroughly researching a weight-loss approach before trying it, as well as nutrition fundamentals such as proper hydration. While her experience shows that IF is trendy (she has 189,000 YouTube subscribers), it doesn’t portray it as a magic bullet: Wright also limited calories.

I took a personal interest in IF after a doctor’s appointment at which I discovered that I was 20 pounds over my happy weight. I talked to my physician and did some online research. I also chatted with my friend Beverly Greene, 76, who had been doing IF for more than a year at the time and had dropped 12 pounds. She skips dinner and reported that her late-afternoon hunger had all but disappeared — and her acid reflux was less severe. “I wish I’d known about it at 50,” she told me.

I decided to try IF for myself. If you’re curious about the craze, read on for answers to some commonly asked questions.

Is it safe for me? IF may be an option for many people, but according to Kristen Gradney, dietitian and nutritionist spokesperson for the Academy of Nutrition and Dietetics, individuals diagnosed with diabetes or who are on diabetes medications should only attempt it under the close supervision of a physician. Ask your health care provider if it’s a good move for you.

How does it work? Monique Tello, a physician at Massachusetts General Hospital, explained it like this in the Harvard Health Blog: Everything we eat is broken down by enzymes and ends up as molecules in our bloodstream. Carbohydrates, for example, are reduced to sugars, which the body uses for energy. If we eat more sugar than we need, the excess is delivered to our fat cells by the hormone insulin and stored as fat. But a few hours after eating (provided we haven’t snacked), insulin levels drop, cueing our fat cells to release stored sugar for energy. The idea is that IF allows our insulin levels to drop low enough, and stay low long enough, that our bodies burn fat and we lose weight.

Besides weight loss, how else does IF change the body? IF may protect against diabetes and cardiovascular disease, according to a 2017 report from the National Institutes of Health (NIH). A 2018 study of overweight men in the journal Cell Metabolism found improvements in blood pressure after IF. But future, more inclusive research would help to confirm or clarify these findings.

Isn’t skipping breakfast discouraged by many health experts? More research is needed to better understand how morning eating habits affect weight control. According to a study published in April in the Journal of the American College of Cardiology, researchers found a link between skipping breakfast and deaths by heart attack. “Our study supports the benefits of eating breakfast in promoting cardiovascular health,” they said. Plus, breakfast fuels our body and muscles, and it can help us avoid cravings, dietitian Katherine Zeratsky writes on MayoClinic.org. Fasting in the evening and eating in the morning may be a more beneficial option.

Do you need to cut calories? Simply by restricting your mealtimes during IF, you may cut your caloric intake. But eating within an eight-hour window doesn’t mean you can gorge on whatever you want. I was advised by Gradney to eat a Mediterranean diet — lean protein, legumes, fruits and vegetables — and drink tons of water. According to Gradney, “You need some carbs to feed your brain, your muscles and fuel yourself. But fruits and vegetables should be the primary source.” Also, you’re allowed to have coffee, tea and water during fasting hours.

What’s it like in real life? Experiences can vary. Real talk: My first few days on IF were terrible. I had a tough time concentrating and endured what felt like a week-long headache. The good news: Because I eat pretty healthy, meaning I don’t eat fast food, beef or pork, and I consume several servings of vegetables and fruit daily, I didn’t have to significantly change what I ate. I did watch my sugar intake and limited myself to one alcoholic drink per week.

Here’s my conclusion: Giving up nighttime snacking was hard. And when I’d go out to dinner, my 16-hour fast couldn’t start until after the final bite, which meant that sometimes I couldn’t eat until midafternoon the next day. But after about a month, I’d lost six pounds and noticed I had a lot more energy, even when I didn’t get a great night’s sleep.

Gradney cautioned me that over the long term my weight loss might be modest, but since IF can increase metabolism, it may help followers avoid future weight gain. I chose not to continue with the program, as I found that I loved breakfast way too much! 

Rebekah Sager is an award-winning journalist and published author with over a decade of experience. She has contributed to the Washington Post, Hollywood Reporter, Playboy, VICE, and more. Her work is featured in the anthology “Chicken Soup for the Soul: I'm Speaking Now: Black Women Share Their Truth in 101 Stories of Love, Courage, and Hope.” She is a senior staff writer with Daily Kos.