By Dr. Mercola
Research1 published in the journal Cell Metabolism concluded that time-restricted eating not only prevented but also reversed obesity and related metabolic dysfunction.
Indeed, intermittent fasting is one of the most effective interventions I’ve found to reverse insulin resistance, shed excess weight, and improve body composition.2 Two core mechanisms responsible for these benefits are:
- Improved insulin and leptin sensitivity
- Triggering your body to more effectively burn fat for fuel
Intermittent fasting also has other health benefits that can be valuable for just about anyone—including increased longevity and neuroprotective benefits—but if you’re not insulin resistant, it’s not as crucial.
If you’re among the minority of Americans who do not struggle with insulin resistance, then my general recommendation is to simply avoid eating at least three hours before bedtime. That automatically allows you to “fast” for at least 11 hours or longer depending on if and when you eat breakfast.
Efforts to Develop Intermittent Fasting as an FDA-Approved Cancer Treatment Underway
Interestingly, one research group is reportedly working on getting intermittent fasting approved by the US Food and Drug Administration (FDA) as an adjunct therapy for cancer patients.
Earlier research has demonstrated that calorie restriction helps extend the lifespan of animals by improving insulin sensitivity and inhibiting the mTOR pathway. Fasting has also been shown to “starve” cancer cells while simultaneously protecting cells from chemotherapy toxicity.
Intermittent fasting—which is easier to comply with—has been found to have very similar effects, and researchers are now looking at using intermittent fasting to augment cancer treatments and improve long-term survival rates.3
One recent study,4 published in the journal Cell Metabolism, found that bimonthly cycles of four-day long low-calorie intake produced multi-system regeneration in mice.
Visceral belly fat was reduced, and the risk for cancer and inflammatory diseases declined. Meanwhile, immune and brain function improved, and lifespan was increased. In the mouse brain, neurons were regenerated, improving learning and memory.
“The mouse tests were part of a three-tiered study on periodic fasting's effects - testing yeast, mice and humans. Mice, which have relatively short life spans, provided details about fasting's lifelong effects.
Yeast, which are simpler organisms, allowed researchers to uncover the biological mechanisms that fasting triggers at a cellular level. And a pilot study in humans found evidence that the mouse and yeast studies were, indeed, applicable to humans...
In a pilot human trial, three cycles of a similar diet given to 19 subjects once a month for five days decreased risk factors and biomarkers for aging, diabetes, cardiovascular disease and cancer with no major adverse side effects.”
Intermittent Fasting Reprograms Your Body to Age Slower and Rejuvenate Faster
In the human pilot study, the participants’ calorie intake was reduced to 34-54 percent of their normal for a period of five days once a month. The meals had a nutrient composition of:
- 9-10 percent proteins
- 34–47 percent carbohydrates
- 44–56 percent fat
One of the ways intermittent calorie restriction appears to reduce cancer risk is by decreasing IGF-1—a hormone linked to aging and cancer susceptibility. According to co-author Valter Longo:7
“Strict fasting is hard for people to stick to, and it can also be dangerous, so we developed a complex diet that triggers the same effects in the body. I’ve personally tried both, and the fasting mimicking diet (FMD) is a lot easier and also a lot safer.
It’s about reprogramming the body so it enters a slower aging mode, but also rejuvenating it through stem cell-based regeneration. It’s not a typical diet because it isn’t something you need to stay on.”
As reported by the University of Southern California:8
“Longo believes that for most normal people, the FMD can be done every three to six months, depending on the abdominal circumference and health status.
For obese subjects or those with elevated disease risk factors, the FMD could be recommended by the physician as often as once every two weeks. His group is testing its effect in a randomized clinical trial, which will be completed soon, with more than 70 subjects.
‘If the results remain as positive as the current ones, I believe this FMD will represent the first safe and effective intervention to promote positive changes associated with longevity and health span, which can be recommended by a physician,’ Longo said.
‘We will soon meet with FDA officers to pursue several FDA claims for disease prevention and treatment.’”
How Fasting Affects Your Body
Researchers have repeatedly and consistently concluded that fasting—which includes not only eating less food overall, but also eating less frequently—can have a beneficial effect on a wide array of biological functions and systems.
One 2013 review9 found a broad range of therapeutic potential of intermittent fasting, even when total calorie intake per day did not change, or was only slightly reduced. Research included in that review, and other published studies, indicate that intermittent fasting can help:
Limit inflammation; reduce oxidative stress and cellular damage Improve circulating glucose Reduce blood pressure Improve metabolic efficiency and body composition, including significant reductions in body weight in obese individuals Reduce LDL and total cholesterol levels Prevent or reverse type 2 diabetes, as well as slow its progression Improve immune function,10 and shift stem cells from a dormant state to a state of self-renewal Improve pancreatic function Improve insulin and leptin levels and insulin/leptin sensitivity Reproduce some of the cardiovascular benefits associated with physical exercise Protect against cardiovascular disease Modulate levels of dangerous visceral fat Boost mitochondrial energy efficiency Normalize ghrelin levels, known as “the hunger hormone.” Help eliminate sugar cravings as your body adapts to burning fat instead of sugar Promote human growth hormone production (HGH). Fasting can raise HGH by as much as 1,300 percent in women and 2,000 percent in men.11 HGH plays an important part in health, fitness, and slowing the aging process. It’s also a fat-burning hormone Lower triglyceride levels and improve other biomarkers of disease Boost production of brain-derived neurotrophic factor (BDNF), stimulating the release of new brain cells and triggering brain chemicals that protect against changes associated with Alzheimer’s and Parkinson’s disease. (Alternate-day fasting—restricting your meals on fasting days to about 600 calories—can boost BDNF by 50 to 400 percent, depending on the region of the brain.12
Choosing an Intermittent Fasting Plan
There are a variety of intermittent fasting schedules, and the ideal one is the one you will actually follow. As a general rule, it involves cutting calories in whole or in part, either a couple of days per week, every other day, or even daily. The one I recommend and have personally used involves restricting your daily eating to an eating window of 6-8 hours. Compliance is a critical factor in any of these approaches and it seems this is one of the easiest intermittent fasting schedules to implement and maintain—especially once your body has shifted over to burning fat instead of sugar as its primary fuel.
Fat, being a slow-burning fuel, allows you to keep going without suffering from the dramatic energy crashes associated with sugar. And, if you’re not hungry, then not eating for several hours is no big deal. If you’re insulin/leptin resistant, I recommend doing this every day until your weight, blood pressure, cholesterol ratios and/or diabetes normalizes. At that point, simply do it as often as you need to maintain your healthy state.
The 5:2 Intermittent Fasting Plan
Another popular intermittent fasting schedule is the 5:2 plan, promoted by Dr. Michael Mosley in his book, The Fast Diet: Lose Weight, Stay Healthy, and Live Longer with the Simple Secret of Intermittent Fasting.13 It involves eating normally for five days per week, and fasting for two days. On fasting days, he recommends cutting your food down to one-fourth of your normal daily caloric intake, or about 600 calories for men and about 500 for women, along with plenty of water and tea.
It doesn’t matter which days you choose as your fasting days. Monday can be a good place to start if you’re fired up at the beginning of a new week or if you’ve “feasted” over the weekend. On a fasting day, you can spread your 500/600 calories throughout the day, or you might choose to enjoy them all at an evening meal. Just find the routine that works best for you. Dr. Mosley offers three “golden rules” for success:14
- Be sensible on non-fasting days. Eat normally, enjoy treats in moderation, but avoid bingeing.
- Watch what you drink. Juices, lattes, alcohol, fizzy drinks, and smoothies typically contain a glut of calories and sugar but won’t satisfy your appetite, so avoid them all.
- Try adding another fasting day. Go for a 4:3 pattern (four days of normal eating, three days of reduced calories).
A third variation that is quite common is the alternate day fast. This fasting protocol is exactly as it sounds: one day off, one day on. The drawback is that it requires you to go to bed with an empty stomach every other day, which can be tough for most people—at least initially. This plan, and the science behind it, is detailed in Dr. Krista Varady’s book The Every-Other-Day Diet: The Diet That Lets You Eat All You Want (Half the Time) and Keep the Weight Off.
Dr. Varady’s research shows that alternate-day fasting, where you consume about 500 calories on fasting days and can eat whatever you want on non-fasting days, works equally well for weight loss as complete fasting, and it’s a lot easier to maintain this type of modified fasting regimen.
As an assistant professor of kinesiology and nutrition at the University of Illinois, Dr. Varady has conducted many studies on intermittent fasting. In one of her studies, they found that splitting the 500 calorie meal up into multiple smaller meals throughout the day was not as successful as eating just one meal, once a day. So ideally, eat your low-calorie fasting day meal either for lunch or dinner. The main problem relates to compliance. If you’re truly eating just 500 calories in a day, you will lose weight. But when eating tiny amounts of food multiple times a day, you’re far more inclined to want more, so the cheat rate dramatically increases.
Her research also refutes concerns that intermittent fasting may result in loss of lean body mass.15 I have not found this to be true, and according to Dr. Varady’s research, 90 percent of the weight people lose is body fat, with only 10 percent being lean body mass.16 Moving throughout the day and consuming an appropriate amount of high quality protein will also help minimize loss of muscle mass.
Intermittent Fasting versus Eating Six Small Meals a Day
Traditionally, three square meals a day has been considered key for weight management, but while this may help stabilize blood sugar and insulin levels for some people, it’s important to realize that, historically, humans simply did not have access to food 24/7. The most obvious risk with spreading out your meals to morning, noon, and evening is overeating. Spreading it out over six meals a day magnifies that risk even more—unless you’re truly mindful of eating very, very small snacks or meals.
Avoiding high-sugar foods is also key for both general health and weight loss, no matter how many meals a day you eat. And, one of the near-automatic side effects of eating a diet higher in healthy fat and low in sugars is decreased hunger and cravings. So if you’re getting enough healthy fat in your diet, you may not be hungry enough to actually eat six times a day! The issue of which is better—intermittent fasting or eating six small meals a day—was recently addressed in a US News article,17 which states:
“Even if you consume the same amount of calories you would otherwise, eating six times a day may help you maintain more metabolism-revving muscle mass than you would if you ate less often, according to a 2015 study published in Nutrition Research. Yet, while eating six meals a day might sound like a weight-loss dream, it’s actually a lot of work – and may not be right for everyone, [Martha Belury, professor of human nutrition at The Ohio State University] says.
People who are great with routines respond well to the six-a-day meal plan, for example, but it can be impractical for those who aren’t up for prepping and packing meals to eat throughout the day, at least a few of them at the office. After all, if the goal is weight loss, the meals shouldn’t be drive-thru or candy bars. They need to be home-cooked and balanced, she says. And each meal needs to be small; otherwise, you could end up overeating and packing on the pounds.”
How to Radically Increase Your Intermittent Fasting Success
If the very thought of fasting makes you shudder with anxiety, then you’re in luck! EFT (Emotional Freedom Technique) practitioner Julie Schiffman has a great video for reducing your anxiety about fasting. EFT is a powerful energy psychology tool that has helped hundreds of thousands overcome emotional challenges. It uses acupuncture meridians to help neutralize electrical brain disturbances that emotional wounding can cause. I strongly recommend tapping along with her if you have any hesitation at all about fasting. Being in the right mindset is 90 percent of the challenge, and EFT is a highly effective tool toward that end.