By Dr. Mercola
While there are many potential factors1 contributing to unsuccessful weight loss, if you're struggling with excess weight then when you eat may be just as important as what you eat.
In over 30 years of clinical practice, intermittent fasting is one of the most effective ways to shed excess weight I have ever seen. This is for two reasons:
- It helps improve your insulin and leptin sensitivity
- It "resets" your body to more effectively burn fat for fuel
Eating too close to bedtime is another meal-timing factor that can have serious health consequences.
There's compelling evidence showing that when you supply fuel to your mitochondria at a time when they don't need it, they leak a large number of electrons that liberate reactive oxygen species as free radicals.
These free radicals damage your mitochondrial and eventually nuclear DNA. There's also evidence indicating that cancer cells uniformly have damaged mitochondria, so the last thing you want to do is eat right before bedtime.
But personally I strive for six hours of fasting before bedtime, but at bare minimum, avoid eating at least three hours before going to bed.
If you have serious adrenal challenges then you would likely need to resolve them before implementing intermittent fasting.
Also if your goal is to have large muscles, intermittent fasting would likely not be your best strategy. But personally I believe that working to eliminate your risk of cancer for the goal of living much longer is a far better choice for most of us.
Research Shows Most Americans Eat Four to 15 Times a Day
Research reveals that a vast majority of Americans eat all day long. Most also consume a majority of their daily calories late in the evening, and this type of eating pattern is a recipe for weight gain and metabolic dysfunction.
As reported by LA Times:2
"... Americans' 24/7 culture of work, entertainment, and digital connectivity now also extends to our dietary consumption patterns, new research3 finds.
Americans' erratic, round-the-clock eating patterns, suggests the new study, have probably contributed to an epidemic of obesity and Type 2 diabetes.
But they can be changed, and the restoration of a longer nighttime 'fast' shows promise as a means to lower weight and better health..."
The study4 revealed that most participants spread their eating and drinking over the course of 15 hours each day. About 25 percent of their daily calories were consumed before noon, and more than 35 percent after 6 pm.
Other trends revealed by carefully tracking the timing and content of people's food and beverage intake for three weeks included the following:
- The 10 percent of participants who ate and drank the fewest number of times each day still averaged 4.2 consumption-events per day
- The 10 percent who ate most frequently averaged 15.5 consumption-events daily
- Less than 10 percent of participants went without food for 12 hours or longer
- The majority fasted less than 9 hours a day
- An average of 12 percent of the total calories participants ate each day were consumed after 9 pm
Fasting 12 Hours a Day or More May Be Key for Successful Weight Loss
Previous animal research5 has demonstrated that when mice are allowed to eat whenever they want, they tend to get obese, whereas animals whose food availability is restricted to eight or nine hours a day stay leaner — even though the overall calorie consumption is the same between the two groups.
The mice that fast for 15 to 16 hours a day also had lower levels of inflammation, less fatty liver disease, and healthier cholesterol and metabolic markers, compared to the non-fasting mice.
As noted in the featured article:6
"Pointing to such research, the Salk researchers have suggested that a nightly fast of 10 to 12 hours might do much more than just limit the consumption of excess calories:
Even without changing daily calorie intake, a lengthy nighttime fast appears to 'reset' a circadian clock disturbed by 24/7 feeding and drive up the body's ability to burn off extra calories.
While humans cannot have their chow taken away for half the day, the authors wrote, their 'erratic daily rhythm of eating/fasting... can be manipulated to obtain desirable health benefits.'"
To evaluate the validity of their claim, the researchers recruited eight of the original study participants for a small pilot study in which the only dietary change made was restricting their eating to a 10 to 12 hour window each day. For the remaining 12 to 14 hours, they fasted. After four months, the participants had lost an average of more than seven pounds. And, while not specifically instructed to cut calories, they ended up reducing their daily calories by an average of 20 percent anyway. Along with weight loss, the participants also reported improved sleep and increased energy levels.
Temporary Fasting Mimics Long-Term Calorie Restriction
Calorie restriction has been one of the very few interventions that has been consistently shown to promote longevity. But living life on the brink of starvation is just too tough for most people. But, as recently demonstrated in a study7 led by Valter Longo, temporary starving yourself every now and then effectively mimics continuous calorie restrictive diets, and provides many of the same health benefits.
The researchers tested a fasting schedule on yeast, mice, and humans, to evaluate the effects. Thirty-eight healthy individuals between the age of 18 and 70 were enrolled in the human portion of the study. Half of them ate normally throughout the three-month long trial. The other half fasted for five days each month.
During the five fasting days, their diet was all plant-based, low in carbohydrates and protein, and high in healthy fat. On the first day, they ate about 1,090 calories, and then only 725 calories on the remaining four days. As reported by the Detroit Free Press:8
"The test subjects who ate the special diet experienced drops in their fasting blood glucose levels and in factors associated with cancer and cardiovascular risk. In mice, the researchers saw increased numbers of stem cells, suggesting that starvation-like conditions killed off old, weaker cells and allowed younger, refreshed cells to emerge. 'Everything is getting a little younger and it goes back to working much better,' Longo said."
Evidence-Based Health Benefits of Intermittent Fasting
✓ Improved cellular repair and waste removal processes
✓ Reduced cancer risk
✓ Hormonal adjustments that help release stored body fat, such as reduced insulin levels and increased human growth hormone (HGH) release
✓ Improvements in risk factors for heart disease, such as blood pressure, cholesterol levels, triglycerides, and inflammatory markers
✓ Beneficial genetic and molecular changes associated with longevity and disease prevention
✓ Improved brain health and reduced risk for neurodegenerative diseases such as Alzheimer's (courtesy of reductions in inflammation, oxidative stress, reduced blood sugar levels, and improved insulin sensitivity)
✓ Reduced oxidative stress and inflammation
✓ Extended lifespan
Intermittent Fasting Schedules
Intermittent fasting covers an array of different fasting schedules. As a general rule however, intermittent fasting involves cutting calories in whole or in part, either a couple of days a week, every other day, or even daily, as in the case of the scheduled eating regimen I use myself. The "best" one for you is the one you will actually adhere to. Here's a quick summary of several different eating schedules:
✓ Restrict daily eating to 6 to 8 hour window (the key here is to eat breakfast or dinner, but not both)
For the last couple of years, I've suggested skipping breakfast, and having lunch be your first meal. However, some people really struggle without breakfast. More recently, I have refined my views on this strategy. It likely doesn't matter which meal you skip — breakfast or dinner — as long as you skip one of them. The key to remember is to only eat within a window of six to eight consecutive hours each day, and avoiding food for at least three hours before bedtime.
As long as you restrict your eating to this window, you can choose between having breakfast and lunch, or lunch and dinner, but avoid having both breakfast and dinner. If you chose to eat dinner, it's important to avoid eating for at least three hours before going to bed.
I have recently appreciated that this is another important factor that can help optimize your mitochondrial function and prevent cellular damage from occurring.
✓ The 5:2 Fast11
On the 5:2 plan, which Dr. Michael Mosley is a major proponent of, you cut your food down to one-fourth of your normal daily calories on fasting days (about 600 calories for men and about 500 for women), along with plenty of water and tea. On the other five days of the week, you can eat normally.
✓ Alternate Day Fasting
Dr. Krista Varady is a proponent of the alternate day fasting protocol, which is exactly as it sounds: one day off, one day on. When you include sleeping time, the fast can end up being as long as 32 to 36 hours.
✓ The Warrior Diet (by Ori Hofmekler)
This is a protocol designed to improve your fitness by exercising in a fasted state. I've interviewed Ori and posted detailed articles on this in the past. His plan calls for 20 hours of fasting, and four hours of "feasting." You exercise during the day in a fasted state. Raw vegetables are allowed during your fast, but no protein, which is reserved for "feasting" or post-exercise recovery meals. To learn more about the Warrior Diet, please see this previous interview with Ori.
✓ Eat Stop Eat (created by Brad Pilon12)
In this protocol, you fast for a full 24 hours once or twice a week. Your fast should be broken with a regular-sized meal (i.e. avoid gorging when coming off your fast), and you can maintain a regular exercise program without any special diet recommendations for workout days.
Fasting for 24 hours can be tough for some people, but eating a high-fat, low-carb diet can make 24-hour fasting easier, as a higher fat diet will tend to normalize your hunger hormones and provide improved satiety for longer periods of time.
✓ LeanGains (a fasting protocol by Martin Berkhan13)
This is a daily 14 to 16 hour fast, during which time you consume nothing with the exception of non-caloric fluids. Sleeping time is included in this time-frame, leaving an 8 to 10 hour window during the day when you're allowed to eat.
This protocol is designed with regular exercise in mind, with specific nutrient ratios for workout days and rest days, and is geared for those who want to shed excess fat and gain muscle mass. Hence, it's best suited for those who are actually exercising and lifting weights each week and can tolerate working out in a fasted state.
Must You Intermittently Fast for Life?
While many end up sticking to intermittent fasting long-term once they get used to it, you don't have to continue on forever if it doesn't appeal to you long-term. If you need to lose 50 pounds, you're looking at about six months or so of intermittent fasting, after which you can revert back to eating more regularly. Just keep an eye on your insulin sensitivity; if your insulin level starts to rise back up, you may want to go back on an intermittent fasting schedule again for a period of time. I strongly recommend paying careful attention to your food choices, however. Even on non-fasting days, I believe it's important to eat a diet that is:
- Based on REAL FOOD, ideally organic and/or locally grown.
- High in healthy fats. Those who are insulin resistant will benefit from 50 to 85 percent of their daily calories in the form of healthy fat from avocados, organic grass-fed butter, pastured egg yolks, coconut oil, and raw nuts.
- Moderate amounts of high-quality protein from organically raised, grass-fed or pastured animals. Most will likely not need more than 40 to 80 grams of protein per day.
- Unrestricted amounts of fresh vegetables, ideally organic.
The Benefits of Avoiding Late-Night Eating
As mentioned earlier, eating too close to bedtime is another meal-timing factor that can sabotage your health. It's important to have a minimum of three hours after your last food intake before you go to bed. Ideally, aim for as much as six hours between your last meal and your scheduled bedtime.
The rationale for this recommendation has to do with the way your body produces energy. Your mitochondria are responsible for "burning" the fuel your body consumes and converting it into usable energy. These tiny bacterial derivatives live inside your cell and are optimized to create energy from the food you eat and the oxygen in the air you breathe. Your cells have between 100 and 100,000 mitochondria.
Your mitochondria have a series of electron transport chains in which they pass electrons from the reduced form of the food you eat to and combine it with oxygen from the air you breathe to form water. This process drives protons across the mitochondrial membrane, which recharges ATP (adenosine triphosphate) from ADP (adenosine diphosphate). ATP is the carrier of energy throughout your body.
A major side effect of this transfer of electrons is that some leak from the electron transport chain to react with oxygen to form the free radical superoxide. Superoxide anion, the product of a one electron reduction of oxygen, is the precursor of most reactive oxygen species and a mediator in oxidative chain reactions. These oxygen free radicals attack the lipids in your cell membranes, protein receptors, enzymes, and DNA that can prematurely kill your mitochondria.
Please understand that some free radicals are actually good and your body requires them to regulate cellular function. The problem is when you have excessive free radical production. Sadly that is the case for the majority of the population and why most diseases, especially cancers, are acquired. There are two possible solutions, increase your antioxidants or reduce mitochondrial free radical production.
I believe one of the best strategies for reducing mitochondrial free radical production is to limit the amount of fuel you feed your body when it requires the least amount, which is when you are sleeping. If you feed your body shortly before sleeping you will have large amounts of fuel your body simply has no need for, which will result in a massive increase in leakage of electrons that combine with oxygen to form free radicals, which damage your DNA, and thereby radically increases your risk of cancer.
This is one of the reasons why I rarely eat less than three hours before going to bed and frequently it is 5 to 6 hours. A review paper14 that provides much of the experimental work for the above explanation was published in 2011, titled "Mitochondrial DNA Damage and Animal Longevity: Insights from Comparative Studies."
It may be too complex for many laypeople, but the take-home message is that since your body uses the least amount of calories when sleeping, you'll want to avoid eating close to bedtime because adding excess fuel at this time will generate excessive free radicals that will damage your tissues, accelerate aging, and contribute to chronic disease.
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 practitioner Julie Schiffman has a great video for reducing your anxiety about fasting.
EFT, or the Emotional Freedom Techniques, 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.
Contraindications for Intermittent Fasting
While intermittent fasting has many health benefits and has been shown to be a very effective strategy for weight loss, it's not for everyone, all the time. It's also important to remember that when you're fasting, proper nutrition becomes even MORE important, so if you're currently on a processed food diet, you may be better off addressing the foods you eat FIRST. Your focus should be on eating REAL FOOD.
Once you've gotten the hang of cooking from scratch, then you can begin experimenting with intermittent fasting. For many, switching out processed foods for whole foods can go a very long way toward addressing excess weight and insulin resistance — especially in combination with regular exercise.
All of that said, there are some instances in which fasting may be contraindicated. If you're hypoglycemic, diabetic, or pregnant (and/or breastfeeding), you are better off avoiding any type of fasting or timed meal schedule until you've normalized your blood glucose and insulin levels, or weaned the baby. Other categories of people that would be best served to avoid fasting include those living with chronic stress, and those with cortisol dysregulation, or those that are seeking to athletically compete and build large muscle mass.
One of the keys to eliminating hypoglycemia is to eliminate sugars, especially fructose from your diet. It will also be helpful to eliminate grains, and replace them with higher amounts of quality proteins and healthful fats. However it will take some time for your blood sugar to normalize.
You'll want to pay careful attention to hypoglycemic signs and symptoms, and if you suspect that you're crashing, make sure to eat something. The ideal food would be coconut oil as it will not worsen your insulin levels and is metabolized relatively quickly for energy.
As for pregnant and/or lactating women, I don't think fasting would be a wise choice. Your baby needs plenty of nutrients, during and after birth, and there's no research supporting fasting during this important time. Instead, focus on improving your nutrition during this crucial time.
A diet with plenty of raw organic, biodynamic foods, and foods high in healthy fats, coupled with high quality proteins will give your baby a head start on good health. You'll also want to be sure to optimize your vitamin D levels and include plenty of cultured and fermented foods to optimize your — and consequently your baby's — gut flora. For more information, please see this previous article that includes specific dietary recommendations for a healthy pregnancy, as well as my interview with Dr. Natasha Campbell-McBride.