Intermittent Fasting May Help Support Brain and Body

While typical diets are built around restrictive lists of foods that you should and shouldn’t eat, one of the most popular strategies in recent years takes a very different tack. Intermittent fasting focuses on when you should eat, not what.

More of an eating pattern than a diet, intermittent fasting doesn’t exclude specific food groups, such as carbohydrates, fats, sugar or animal protein, which may be part of its appeal. The idea is that by restricting the number of hours we can be munching, we will reduce our calorie intake.

In addition, the science suggests that daily fasting for a long block of time — for example, after dinner ends at 7 or 8 p.m. until around 11 a.m. the next morning — helps reduce the levels of insulin, blood pressure and cholesterol and causes the body to burn off more fat.

It’s also a pattern of eating that is more in sync with the way the human body naturally operates. Our metabolism is programmed for daytime eating and nighttime sleep. Eating at night can throw off this balance, leading to weight gain and a greater risk of diabetes and heart disease, to say nothing of sleep problems, studies show.

For people at midlife and older, there may be additional benefits. Studies of older adults using intermittent fasting suggest that it can help reduce inflammation in some people, and several studies found it was linked to improvements in short-term memory in older adults. Intermittent fasting may also help cells clear out damaged cells, which could potentially improve brain function.

Fasting is nothing new, of course. It’s been practiced throughout history for cultural and religious reasons. The current version took off in 2012 with a documentary by BBC broadcast journalist and physician Michael Mosley called “Eat, Fast, Live Longer,” followed by books like The 5:2 Diet by Kate Harrison and internist Jason Fung’s 2016 bestseller The Obesity Code.”

The strategies for intermittent fasting generally fall into two categories: a daily window of around eight hours for meals followed by fasting, or the so-called 5:2 weekly method, in which people eat normally for five days, but gradually limit themselves to just 500 to 600 calories on each of two nonconsecutive days.

No matter which strategy you choose, talk to your doctor before trying a fasting plan, stay well-hydrated and choose healthy foods for meals. Those with chronic diseases or who need to take medication at specific times or who have had problems with disordered eating should also take particular care and caution before trying any fasting plan.

Many find the daily meal window method easier to follow than the 5:2 weekly plan where you’re “hardly eating anything two days a week,” Mark Mattson, a neuroscientist with Johns Hopkins University School of Medicine, who has been researching intermittent fasting for 25 years and following it himself since the 1980s, said in an interview.

Fasting 16 hours, from the end of dinnertime to late morning the next day, “is enough to trigger changes in the brain and body, studies suggest,” Mattson said, although it may take the body several weeks to adjust to the new way of eating. And by the way, if you’re caffeine-dependent, having unsweetened coffee or tea in the morning instead of an early breakfast won’t break the fast.

For those who can’t skip breakfast in the morning, Lauri Wright, a spokesperson for the Florida Academy of Nutrition and Dietetics and chair of the department of nutrition and dietetics at the University of North Florida, suggests narrowing the fasting window to eight to 12 hours, with “the bulk of the fast occurring while you sleep,” she said in an email.

The idea, says Mattson, “particularly in people who are overweight, is to use intermittent fasting to change their eating pattern, which may help them keep their weight within healthier limits and also have some cognitive benefits. Exercise and keeping intellectually engaged is also important.”

Mattson and coauthor Rafael de Cabo of the National Institute on Aging, published a paper in December 2019 in the New England Journal of Medicine that reviewed the current state of intermittent fasting research in both animals and humans. 

They wrote that studies and clinical trials show that “intermittent fasting has broad-spectrum benefits for many health conditions, such as obesity, diabetes mellitus, cardiovascular disease, cancers and neurologic disorders.”

Animal studies, which make up the bulk of intermittent fasting research, suggest that intermittent fasting improves an animal’s health throughout its life span. Human studies, however, have mainly looked at fasting’s effects over several months, so “it remains to be determined whether people can maintain intermittent fasting for years.” And results of research in animals doesn’t always translate to the same results for research in humans.

What you need to know:

• It’s not for everyone. Dietitian Lauri Wright admits she’s not a huge fan of intermittent fasting. Some of her older clients have tried it, but have found it hard to stick with. She worries that “fasting can make some people feel lightheaded or dizzy, which could increase the risk of a fall. I also worry about seniors getting adequate nutrients while intermittent fasting, especially protein.”
• Talk to your health provider first. “Anyone considering intermittent fasting should first discuss it with a doctor, especially if they’re taking medications that may need to be adjusted, have a chronic disease or a history of eating disorders or disordered eating,” Wright advises. A better idea may be working with a registered dietitian who can individualize a meal plan to fit your needs and goals.