Your Mom Was Right
My friend Nancy has been intermittently fasting for about a year now. She started by eating for eight hours and fasting for sixteen. Now she eats only one meal daily and occasionally fasts for multiple days.
“Without a shadow of a doubt, it’s one of the best things I have ever done for my health. I plan to continue for life,” she says.
Intermittent fasting is so popular that in 2019, February was declared National Fasting Month.
What is intermittent fasting?
You’re already intermittently fasting at night when you sleep. The idea behind the new fasting fad is to extend that period of not-eating for a couple of hours or longer. Maybe you postpone breakfast or skip it altogether. Maybe you skip dinner instead.
Instead of being considered starvation, skipping meals is now considered healthy. “In the past century, a shift has occurred away from disease caused by insufficient nutrient supply towards over-nutrition, leading to obesity and diabetes, atherosclerosis, and cardiometabolic disease,” explained a 2018 report from the Washington University School of Medicine.
Intermittent fasting is an outgrowth of research into caloric restriction. First theorized in the early 1900s, experiments on animals throughout the 20th century demonstrated an extended lifespan resulted from the reduction of caloric intake by a third.
The National Institute of Aging began a clinical trial on humans in 2002 called CALERIE. CALERIE studied human participants over a series of years. The trial results supported previous research, connecting “sustained human calorie restriction (for at least two years) and the favorable effects on predictors of longevity and cardiometabolic risk factors.”
What’s the difference between intermittent fasting and caloric restriction? Caloric restriction means you eat as often as you like, but substantially fewer calories. Intermittent fasting features two or three meals compressed into a short period of time, with more rest and digestion time before dinner and breakfast.
During that increased digestion time, your body shifts over to burning fat. “After about 8 hours of fasting, the liver will use the last of its glucose reserves. At this point, the body enters into a state called gluconeogenesis, marking the body’s transition into fasting mode. Studies have shown that gluconeogenesis increases the number of calories the body burns. With no carbohydrates coming in, the body creates its own glucose using mainly fat,” Medical News Today reported.
In no way are either caloric restriction or intermittent fasting intended to create starvation or anorexia. The key here is that you have to eat a regular meal at some point, or your body will go into starvation mode and begin eating muscle when it runs out of fat.
But burning fat while you sleep sounds pretty good, right?
What are the health benefits?
With the exception of CALERIE, most research has been done on rats. In rodents, intermittent fasting improves their overall health and lowers the risk of retinopathy in diabetic rats.
A recent literature review published in the New England Journal of Medicine summarizes the available research to date: “Preclinical studies and clinical trials have shown that intermittent fasting has broad-spectrum benefits for many health conditions, such as obesity, diabetes mellitus, cardiovascular disease, cancers, and neurologic disorders.”
However, almost all of the studies cited in the review article test caloric restriction or alternate day fasting, rather than daily intermittent fasting. For instance, three diabetic patients in Canada were able to cease insulin treatment via alternate day fasting.
One recent study seems particularly promising. A 2018 paper from Columbus State University in Georgia and Pennington Biomedical Research Center in Louisiana tested intermittent fasting tied to circadian rhythms. For five weeks, eight pre-diabetic men stopped eating at in the afternoon and resumed eating at sunrise.
“Our proof-of-concept study also constitutes the first trial of early time-restricted feeding (eTRF), a form of IF that involves eating early in the day to be in alignment with circadian rhythms in metabolism,” the researchers wrote.
Participants ate during a six-hour window beginning at sunrise and ending by 3pm. Their menus included waffles, oatmeal, pasta, white meat and fish; there was no weight loss goal included in the study.
The resulting improvements in blood pressure and insulin sensitivity (cholesterol did not improve) disappeared when the men were switched back to a twelve-hour eating window.
Blood pressure and insulin sensitivity levels worsened even more when the men were switched to a six-hour eating window late in the day, signaling the importance of eating earlier rather than later.
How do you do it?
While that study had limitations for everyday practical use — it only included eight men and no women, test subjects were pre-diabetic — it does seem evident that some health improvements can be gained by eating earlier in the day and fasting longer overnight. So: dinner earlier, no night snacking.
Generally speaking, you don’t get the benefits of fasting if you eat whatever you want. You still have to eat healthfully and moderately. Even the men in the circadian rhythm study ate little red meat or high-fat foods. In that regard, there is an element of caloric restriction in it: you can’t overeat or eat junk during your mealtimes and expect to benefit.
There’s an app called Zero that will help you select and stick to a level of fasting. After you chose the number of hours you’d like to fast, it provides you with a countdown clock. And of course, like every app, after you complete a fast you receive a badge. It’s helpful at first but after you get on a schedule, you may find you don’t need it.
However long you choose to fast, be careful to choose a length of time that doesn’t leave you ravenous at the end. Personally speaking, if I don’t eat for 18 hours, I will eat everything within sight when my fast ends. A sixteen hour fast is achievable for me and doesn’t result in bingeing.
As for Nancy? She’s seen most of her bloodwork improve (not her lipids), and she says her chronic pain, acid reflux and inflammation are gone. I haven’t been fasting for as long as she, but I can also say my acid reflux has greatly improved.
Unfortunately, like the men in that last study, I haven’t lost so much as a pound.