By Dr. Mercola
Intriguing new research is adding weight to the notion that when you eat could be just as important as what you eat... and possibly even more so.
You're probably aware that your body runs on a regular circadian rhythm that coincides with when you sleep and wake.
But each of your organs, including your liver, muscle, fat and gut, have their own clock, and certain organs work best at different times of the day.
Earlier studies support this premise, indicating that nighttime eating may contribute to weight gain; the latest study took this a step further and showed that nighttime fasting may be a powerful weight loss tool.
Is Fasting for 16 Hours Overnight the Key to Weight Loss?
Researchers from the Salk Institute fed mice a high-fat, high-calorie diet but altered when they were able to eat. One group had access to food both day and night, while the other group had access to food for only eight hours at night (the most active period for mice). In human terms, this would mean eating only for 8 hours during the day.
Despite consuming the same number of calories, mice that had access to food for only eight hours stayed lean and did not develop health problems like high blood sugar or chronic inflammation.1 They even had improved endurance motor coordination on the exercise wheel. The all-day access group, on the other hand, became obese and were plagued with health problems including:
- High cholesterol
- High blood sugar
- Fatty liver disease
- Metabolic problems
This suggests that your body may benefit from the break it receives while fasting, whereas constant eating may lead to metabolic exhaustion and health consequences like weight gain. Researchers said their latest work shows it's possible to stave off metabolic disease by simply restricting when you eat with periodic fasting, or even by just keeping to regular meal schedules rather than "grazing" off and on all day.
"[Time-restricted feeding] is a nonpharmacological strategy against obesity and associated diseases."
Intermittent Fasting May be a Secret to Optimal Health and Weight Loss
Because of the research above, combined with many other compelling pieces of evidence, some mentioned below, I have revised my personal eating schedule to eliminate breakfast and restrict the time I eat food to about seven to eight hours, which is typically from noon to 6 or 7 p.m. Just seems to make sense that our ancestors rarely had access to food 24/7 like we do and our genes are optimized for intermittent fasting.
It takes about six to eight hours for your body to metabolize your glycogen stores and after that you actually start to shift to burning fat. However, if you are replenishing your glycogen by eating every eight hours, you make it far more difficult for your body to use your fat stores as fuel.
It's long been known that restricting calories in certain animals can increase their lifespan by as much as 50 percent, but more recent research suggests that sudden and intermittent calorie restriction appears to provide the same health benefits as constant calorie restriction, which may be helpful for those who cannot successfully reduce their everyday calorie intake (or aren't willing to).
Fasting has been used as a spiritual practice in many cultures since ancient times, but it might have been done for health purposes as well. Modern science has confirmed there are many health reasons for fasting, including:
- Normalizing your insulin sensitivity, which is key for optimal health as insulin resistance (which is what you get when your insulin sensitivity plummets) is a primary contributing factor to nearly all chronic disease, from diabetes to heart disease and even cancer
- Normalizing ghrelin levels, also known as "the hunger hormone"
- Promoting human growth hormone (HGH) production, which plays an important part in health, fitness and slowing the aging process
- Lowering triglyceride levels
- Reducing inflammation and lessening free radical damage
A recent animal study published in the International Journal of Endocrinology showed a beneficial glycemic effect that resulted in a lower gain in body weight than in non-fasting animals.2 Other research suggests fasting triggers a variety of health-promoting hormonal and metabolic changes similar to those that occur when you exercise, which may help prevent age-related brain shrinkage and other chronic and debilitating diseases such as Alzheimer's and Parkinson's. As for weight loss, here are three studies from recent years investigating fasting for weight loss, all of which showed positive results:
- Non-obese patients lost an average of four percent of their total fat with alternate-day fasting for 22 days. Their fasting insulin also decreased.3
- Alternate-day fasting was also effective for obese patients in a 2009 study. On fasting days, participants consumed 25 percent of their daily calorie needs. On average, they lost just over 5.5 pounds in eight weeks, and about three percent of their total body fat. Total cholesterol and LDL ("bad") cholesterol decreased, while HDL ("good") cholesterol remained unchanged. Systolic blood pressure also decreased.4
- In young, overweight women, alternate-day fasting was just as effective as calorie restriction for promoting weight loss and improving metabolic markers.5
Exercising While Fasting May Be Most Beneficial of All
Recent research suggests fasting before exercise may help you to achieve your fitness results faster by forcing your body to shed fat. This happens because your body's fat burning processes are controlled by your sympathetic nervous system (SNS), and your SNS is activated by both exercise and lack of food. The combination of fasting and exercising maximizes the impact of cellular factors and catalysts (cyclic AMP and AMP Kinases), which force the breakdown of fat and glycogen for energy.
According to some fitness experts, such as Ori Hofmekler, fasting may indeed push your exercise program to the next level. The reason for this is because exercise and fasting yield acute oxidative stress, which is actually essential for maintaining optimal muscle.
Many find it works out well to skip breakfast like I do, exercise, and then break their fast after working out, which would allow you to get the best of both worlds: the benefits of working out in a fasted state, and protein-loading for recovery about half-an-hour to an hour afterward. On the days that I exercise in the morning, I will have two scoops of Pure Power Protein about 30 minutes after the workout to provide nutrients, especially leucine, for muscle growth and repair.
Interestingly, since adopting this approach for the past few months I have lost two inches from my waist size and gained three pounds, which means I have lost body fat and gained muscle mass. This has been a personal experiment of mine to see if I can get back to my high school waist size of 32 inches, even though I weighed 20 pounds less back then.
Fasting is Not Starving Yourself
Fasting does not mean abstaining from ALL food for extended periods of time; this can be dangerous and counterproductive. Rather, intermittent fasting is a dramatic reduction of calorie intake at regular intervals – whether you opt for a 16-, 20-, or 24-hour fast once or twice a week, or fasting every other day, or simply delaying certain meals, such as skipping breakfast and exercising on an empty stomach.
There are many options, and you can discover what works best for you by listening to your body, and going slow; work your way up to full-day fasts if your normal schedule has included multiple meals a day. Or try ending your meals earlier in the evening or late afternoon and fast overnight while you sleep.
If you're hypoglycemic, diabetic, or pregnant (and/or breastfeeding), you need to be extra cautious with fasting, and may be best served to avoid it entirely, until you've normalized your blood glucose and insulin levels, or weaned your baby. But if you're healthy, intermittent fasting is likely to give your health a boost, especially if you've already mastered a nutritious diet, which really should be your first step.
When you cut out or delay meals for fasting purposes, it becomes all the more important to maximize the nutrients when you do eat. Fasting combined with a highly processed, toxin-rich diet is not going to do your health any favors. Instead, review my nutrition plan for ideas of what constitutes a healthy diet, so you'll be armed with the nutrition you need to thrive during your non-fasting hours.