Going long hours without eating isn't good for us, we are often told. Our bodies need fuel regularly. Otherwise, we may become lethargic, tired and hungry. Our thinking can become mushy, our ability to work, and even play, hampered.
Not so fast.
A new report by University of Florida researchers suggests that a certain style of fasting can actually be good for us and, illness and disease aside, can be tried at any age. In fact, the study suggests, a certain rhythm of fasting and feasting is something humans have been capable of for eons.
Of course, any serious shift in diet should be cleared with the family physician, cautions Steve Anton, Ph.D., the academic paper's lead author and a faculty member with the UF Institute on Aging.
The study, published in the journal Obesity, reviewed a number of findings that looked at diets, fasting and the results in subjects of all age groups. What these studies showed was that fasting, especially the increasingly popular intermittent fasting, has high potential for weight loss at any age.
The challenge with long-term fasting is that the body tends to consume not only fat, but lean muscle tissue, Anton, 42, explained. "Most people 50 and older want to lose weight but not the muscle."
A typical intermittent fasting pattern consists of 16 hours of not eating and eight hours for eating in a 24-hour day, Anton said. But there can be lots of flexibility in that pattern.
"With most diets, weight loss is not (just) body fat," he said, "and we want to maintain as much muscle tissue as possible."
So how does intermittent fasting work?
"The body essentially flips a metabolic switch" during fasting, Anton said. This means that the body moves from burning glucose, or sugar, for energy to burning fatty acids and their by-products, called ketones. And during fasting, the body converts fatty acids, which are absorbed by the blood, Anton said.
"This switch can happen after a certain period of fasting," Anton said. Typically, after eight to 12 hours of fasting, the level of ketones in the blood significantly increases, he said.
The intermittent fasting pattern can be individualized. For example, a person might eat his last meal at 8 p.m., sleep eight or more hours and resume eating at noon the next day. Water, black coffee and black tea are allowed during the fast. When the dieter returns to food, there's no restriction, other than good, balanced meals.
Intermittent fasting can be done daily, or as a lifestyle, or it can be done two or three times a week.
In studies of nonhuman subjects, the intermittent fasting diet and that metabolic switch point to the possibility that such a diet pattern may lengthen life spans, improve cognitive and physical performance, lower inflammation and lead to better cardiovascular health, Anton said in the paper.
Author Barbara Grufferman devotes an entire chapter to intermittent fasting in her new book, Love Your Age: The Small-Step Solution to a Better, Longer, Happier Life (2018, National Geographic). She underscores that intermittent fasting is safe for anyone without a serious illness but does not recommend it for people under 18 or people with eating disorders.
"What we eat, how we eat and how much we eat is even more critical" as we get older, she said. "Fasting as a way to improve health has been around for decades."
Grufferman, 61, discovered intermittent fasting about five years ago, and her approach was to work with health professionals to monitor her blood as a way of measuring the effects. "When you are intermittent fasting, your immune system gets a big boost," she discovered. "The white blood cells reproduce rapidly after a fast and that strengthens the entire immune system," she said.
There are other benefits, Grufferman said. "This is a way to lose weight and keep it off if you periodically do intermittent fasting," she said.
But too much of a good thing may be harmful, Grufferman added. "I'm not recommending no food at all. Chronic calorie reduction is not recommended."
The author said she has lost weight and maintained that reduction. "When something works, I feel like more people need to know about it," she said.
"We're living in a country that is overweight with a lot of disease that can be avoided."
For the University of Florida's Anton, more research is needed to determine just how people 50 and older can benefit from intermittent fasting and what patterns are most beneficial.
"Intermittent fasting" is a broad term, Anton said. It can mean different things to different people. For Anton's father, who is in his 70s, it's a daily practice. "He has told me he has more energy when he does it."
Another option would be to practice intermittent fasting on alternate days, eating as much as you want on one day and little or no calories the next, Anton said. "Some people, including myself, have a little cream with their coffee," he confessed. "Don't try to be so perfect that you give up. Perfection is the enemy of success."
The key to a successful experience with intermittent fasting, Anton said, is common sense. "You don't have to (fast) 16 hours the first time. You don't try to run a marathon the first time you exercise.
"It's highly recommended you build up the time so your body gets used to it. Once you've adapted, it becomes part of your lifestyle."
Contact Fred W. Wright Jr. at email@example.com.