We've been told since we were children that we need to eat three square meals a day. But new research shows that we don't need to be eating throughout the course of the day. And in fact, it might even be undermining our health. These insights have given rise to what's known as "intermittent fasting" — the daily restriction of meals and caloric intake. Here's why some health experts believe you should starve yourself just a little bit each day.
Most people associate fasting with juice cleanses or religious rituals — a torturous affair that lasts an entire day if not longer, and the sort of thing that should only be done a couple of times each year. But fasts can encompass any number of different strategies, including routines that simply limit the times when you eat each day, or on certain days of the week.
For example, there's Alternate Day Fasting (ADF) and the Two Day Diet (also known as the 5:2 diet). We'll get into these in just a bit, but what's really starting to take off is daily fasting — the practice of eating only during an 8-hour window of your choosing, and then fasting for the remaining 16 hours of the day.
While some might be inclined to cynically dismiss intermittent fasting as just another fad diet, the scientific evidence in support of daily fasting (or any fasting for that matter) is compelling. Restricting caloric intake for extended periods seems to do a remarkable job of staving off a number of health problems, while yielding some definite benefits.
Now before we get into the details, it's important to note that intermittent fasting is not for everyone. Before you try any of this, you should probably check with your doctor to make sure you're healthy enough to go without food for an extended period — even if it's just a 16 hour stretch. It's also important to note that intermittent fasting is not really meant as a way to lose weight — though it happens to be a good way to regulate food intake.
One of the most important studies in this area was conducted just last year at Salk's Regulatory Biology Laboratory. In an experiment, biologist Satchidananda Panda and colleagues restricted the feeding of mice to — conveniently enough — an 8-hour period each day. The researchers were attempting to study whether obesity and metabolic diseases like diabetes were the result of high-fat diets, or from the disruption of metabolic cycles.
To that end, Panda gave the mice lots of fat to eat. In fact, 60% of the calories consumed were derived from fat (which was meant to simulate foods like chips and ice-cream). The researchers also created a control group that ate the same thing, but these mice could eat any time they wanted (interestingly, as nocturnal creatures, they ate half their meals at night, while grazing on the remainders during the day). As for the restricted group, their 8-hour window was at night.
One hundred days later, the free-for-all group was a mess. They gained weight, developed high cholesterol, high blood glucose, and experienced liver damage and diminished motor control (ouch).
But as for the mice who practiced the intermittent fast, they weighed 28% less and showed no signs of adverse health. And what's remarkable is that both groups ate the same amount of calories from the same fatty food. Not only that, the fasting mice also performed better on exercise tests — including a control group of mice who were eating normal food. (You can check out the study for yourself: "Extended Daily Fasting Overrides Harmful Effects of a High-Fat Diet: Study May Offer Drug-Free Intervention to Prevent Obesity and Diabetes")
As a result, the scientists concluded that time restricted feeding can prevent metabolic diseases — and without having to restrict caloric intake. At least in mice. They theorize that eating willy-nilly throughout the day creates metabolic disturbances to naturally occurring metabolic cycles. Essentially, the scientists say that spreading caloric intake throughout the day perturbs metabolic pathways that are regulated by circadian clocks and nutrient sensors.
It's possible to extrapolate this to humans, too. Though anthropologists are not entirely sure how our paleolithic ancestors ate, it's unlikely that they sat down for breakfast, lunch, and dinner. Those are eating routines from a more modern era — and even then, it's likely that only the wealthy could afford multiple meals in one day. In all likelihood, our ancestors ate one or two big meals a day. And that was it. Consequently, their bodies were likely both adapted for and accustomed to going for extended periods without food during much of the day.
Other studies point to similar conclusions. Take the work of Valter Longo, for example. Longo, who works out of the University of Southern California's Longevity Institute, has studied the effects of intermittent fasting on IGF-1, an insulin-like growth factor.
When we consume food, this hormone keeps our body in "go" mode, where our cells are driven to reproduce and facilitate growth. This is great when we need it, but not so much when we're trying to keep off the weight. Moreover, while it's good for growth, it can also speed up the aging process. And in fact, Longo compares the effect to "driving along with your foot hard on the accelerator pedal."
Intermittent fasting, on the other hand, decreases the body's expression of IGF-1. And it also appears to switch on a number of DNA repair genes. Restricted feeding, says Longo, makes our body go from "growth mode" to "repair mode."
Other research by Krista Varady of University of Illinois in Chicago has looked at the way fasting impacts chronic diseases, like cardiovascular disease, type 2 diabetes, and cancer. Her work, which involves both animal and human test subjects, seeks to compare the effects of intermittent fasting with caloric restriction (an extended low-calorie dietary routine that has known health benefits).
What her animal models showed was that intermittent fasting (in this case, alternate-day fasting) lowers the chances of acquiring diabetes, while also lowering fasting glucose and insulin concentrations — and at rates comparable to caloric restriction.
Her tests on human subjects were not much different, which showed greater insulin-mediated glucose uptake. Her evidence suggested that fasting can increase HDL-cholesterol (that's the good kind), while lowering triacylglycerol concentrations. Fasting had no effect on blood pressure. She concluded her study by suggesting that fasting can modulate several risk factors that are known to bring about various chronic diseases.
Moreover, her study showed that intermittent fasting can offer many of the same benefits of caloric restriction, which includes a slight increase in longevity (though this has been recently thrown into question) and increased insulin sensitivity.
Varady recommends an alternate-day fasting routine in which there's no need to restrict the quantity of foods for one day (yes, really), followed by a day in which no more than 600 calories can be consumed.
Another typical intermittent fast is the so-called "5:2 diet." People using this strategy are encouraged to eat normally for five days of the week, but two days are set aside for the fast in which no more than 600 calories are consumed.
And there's more. In addition to Varady's study, other research shows that intermittent fasting can offer neuroprotective benefits. Studies on humans show that it can help with weight loss and reduce disease risk.
And incredibly, there may even be a link to cancer. Another study study by Varady and M. Hellerstein on mice indicated that both caloric restriction and alternate-day fasting can reduce cancer risk and reduce cell proliferation rates.
Short-term fasting can induce growth hormone secretion in men (which is a problem for guys after they hit 30), it reduces oxidative stress (fasting prevents oxidative damage to cellular proteins by decreasing the accumulation of oxidative radicals in the cell — what contributes to aging and disease onset), and it's good for brain health, mental well-being, and clarity.
And as a study published just last week has shown, restricting calories can also lengthen telomeres — which has a protective effect on our DNA and genetic material, which in turn helps with cellular health (i.e. it helps us extend healthy lifespan).
And for people who wish to maintain a ketogenic diet — a metabolic state in which the body is in a perpetual state of fat burning instead of carbohydrate burning — intermittent fasting is a good way to help the body stay in ketosis.
I actually practice daily intermittent fasting, and I've been doing it for about five months. Admittedly, the first week was difficult, but now I don't give it a second thought. My cravings have largely disappeared, but my stomach starts to grumble in the late stages. I feel great, though, my mood is upbeat, and I'm often full of energy (I also do strength-and-conditioning work, which helps).
My particular routine — which is quite typical for daily intermittent fasters — sees me having my last meal of the day sometime between 6:00 and 8:00 PM. But then I don't eat until 1:00 PM the next day. My lunch is usually a big deal, and I savor every bite (a neat benefit of the daily fast is how much better food suddenly tastes). Likewise, my dinner is also a grand affair. So I basically eat two solid meals each day, and fast for a 16 hour stretch.
I also drink coffee and tea during the fasting period (both without cream and sugar). These are zero calorie foods that have little impact on the body's metabolism. And not only that, caffeine is a known appetite suppressant.
Lastly, I also tend to eat very little carbs. As many people know, carbohydrates are notorious for creating food cravings — carbs cause a kind of negative feedback loop. But as all this new research it's showing, it's not necessarily the kind of foods you eat. Rather, it's the fasting that's important. But that said, I wouldn't tempt fate; it's probably prudent to keep the foods healthy.
As a final note, given that this is a restrictive dietary routine, it's important to keep our health goals in mind as they relate to our daily enjoyment of life. Limiting our eating to such a small window of time could certainly be construed as a draconian measure. If a routine like this threatens to make you miserable, it may simply not be worth the bother.
But for me, it's not a problem, and fits in rather nicely with my overall health strategies.
Images: lev dolgachov/Shutterstock, cath5/Shutterstock, Valter Longo, Krista Varady.