#051 Intermittent Fasting, Weight Loss, Longevity

Intermittent Fasting, Weight Loss, and Longevity

Could the secret to maintaining a normal weight, avoiding chronic medical diseases, and living a long life be as simple as intermittent fasting? Recent research suggests this is true.  Just what is intermittent fasting as is it something you should do?

Caloric Restriction and Longevity

Restricting calories while still getting the right nutrients for health has been shown to dramatically increase the lifespan of everything from the mouse to the monkey.  For example, caloric restriction, without malnutrition, in mice and rats has been shown to not only increase their lifespan by 30-40% but to also allow them to maintain a youthful appearance.

Caloric restriction appears to slow down the aging process through reduced oxidative stress while at the same time protect the heart and help to prevent cancer. Many repair mechanisms in the body are triggered during periods of reduced caloric intake.

Most of us would love to slow down the “sands of time” and maintain our youth and vitality until very late in life.  For me, I would love to be able to ski until well into my 100s.  However, like most of you, I love to eat and could never willingly practice caloric restriction.

These same life extending benefits of intermittent fasting have not yet been proven to occur in humans.  Also, caloric restriction in humans can be potentially dangerous as you have to ensure that you are getting the right nutrients for health or you could quickly undo any potential health benefits of caloric restriction.

The question naturally arises, is there a better way to achieve the same benefits of caloric restriction without all of the “pain” and potential risks? Fortunately, recent data suggest that intermittent fasting may offer the same benefits as caloric restriction.

Intermittent Fasting

Many different forms of intermittent fasting have been proposed and studied over the years.  These have ranged from reducing calories two days each week, popularized in the Fast Diet, to going without food for 12 to 24 hours.

Many different religions have also promoted fasting for spiritual reasons.  Christians, Jews, and Muslims have practiced intermittent fasting for millennia to gain greater spiritual awareness.

For me, growing up in a religious home I was taught from a young age to fast for 24 hours once each month as a means to gain greater spiritual awareness.  Unfortunately, the hunger pain of fasting for 24 hours was usually too intense for me to obtain much spiritual benefit.

Fortunately, recent data has suggested that fasting for shorting periods of time, such as even just 12 hours, could offer the same health benefits as a 24 hour fast.  A twelve hour fast is something that is relatively easy for most people to do and something you may already be doing without realizing it.

As part of my health turn around several years ago, I started intermittent fasting for 12 hours on most days.  This was not something that I specifically set out to do.

Rather, in efforts to lose weight, I told myself that I had to stop eating by 7 pm each night.  By shutting down the kitchen for me at 7 pm, I naturally fasted for about 12 hours each day.  This is now something that I recommend for my patients who are trying to lose weight and live a long and healthy life.

Intermittent Fasting in China’s Longevity Village

Over the last several years, my wife and I have led a research team studying the centenarians in China’s Longevity Village located in Southwest China near the Vietnam border.  Remarkably, this group of people have been able to avoid the chronic medical conditions that plague us in Western countries.  It was common in this rural Chinese village to see people still working full-time in the fields until well into their 80s, 90s, or even 100s free of disease and the need to take medications.

Of the many principles we learned from these people, which will be described in an upcoming book (here is a link to watch our book trailer), one important factor is that they practiced intermittent fasting every day of their lives.  These centenarians all ate an early and light dinner and then went 12+ hours before their next meal.  This was part of their culture and tradition.

Seven Reasons to Become an Intermittent Faster

1. Weight Loss

There have now been several well designed studies demonstrating that intermittent fasting can be a very effective weight loss strategy.  For example, in this study, women randomized to “relative” intermittent fasting two days a week as they were still permitted to eat on these “fast days,” were still able to lose just as much weight as those who cut their caloric intake every day.

From research performed at my hospital in 448 patients, we found that people who practiced intermittent fasting weighed much less than those who do not.  Even more interesting is that these intermittent fasters were not even trying to lose weight!

Personally, reducing calories for just two days a week sounds a lot better, and possibly even more effective, than trying to cut calories every day.  I suspect that the reason for this is that if you reduce calories every day your metabolism slows down so it is hard to gain any ground.  In contrast, with intermittent fasting you can keep your metabolism high while shedding the pounds.

2. Improved Brain Function

When we go without food for as little as 12 hours our body runs out of stored glucose to burn and starts burning fat.  This fat burning process is called ketosis.

By reducing our dependence on glucose for fuel we can protect our brains from the damaging effects of sugar.  Indeed, intermittent fasting has been shown to improve cognitive function and protect against age related degeneration of the neurons in our brains.  Other studies have shown that intermittent fasting boosts brain derived neurotrophic factor (BDNF) which allows us to create new brain connections, repair failing brain cells, and protect healthy brain cells from damage.

Perhaps this is why religious people for millennia have found spiritual enlightenment with intermittent fasting?

3. Prevent or Reverse Cancer

Intermittent fasting is well known to reduce the tumor inducing insulin-like growth factor 1 (IGF-1).  IGF-1 not only increases the risk of cancer but also allows children to grow big and adults to develop increased muscle mass.

Lower levels of IGF-1, from intermittent fasting, have been shown to prevent or even reverse cancer.  A study published this year showed that a drug which blocks IGF-1 can suppress cancer.

Interestingly, there is a rare genetic condition called Laron Syndrome.  People with Laron Syndrome cannot make IGF-1.  As a result, they tend to be dwarfs but yet live exceptionally long lives free of cancer.  Amazingly, if you give Laron Syndrome people IGF-1 during puberty they will grow to a normal height but yet will still be protected against cancer.

There may be other factors also at play which prevent against cancer with intermittent fasting.  One study even reported that intermittent fasting may be as effective as chemotherapy in fighting cancer.  Please note that I am not recommending intermittent fasting as a treatment for cancer.  If you are battling cancer right now or are just interested in trying intermittent fasting, be sure to talk with your physician first before considering intermittent fasting.

4. Prevent Diabetes

The most commonly reported benefit of intermittent fasting in the medical literature is the prevention or reversal of diabetes.  As mentioned above, going without food for 12 or more hours puts our bodies in a ketotic state.  During this period of ketosis, abnormalities in our glucose/insulin metabolism (insulin resistance) can be corrected so that when we resume eating again our body’s will respond appropriately to glucose and insulin.

An interesting study was published on the effect of Ramadan in people with diabetes.  During the month of Ramadan, Muslims fast from dawn to sunset every day.  An added benefit is that for many Muslims, during the month of Ramadan their diabetes may even go into remission.

5. Prevent Heart Disease

Dr. Ben Horne from my hospital has led a number of research studies looking at the role of intermittent fasting to prevent or reverse heart disease.  His studies have uniformly shown that plaque build up, or coronary artery disease, is less common in intermittent fasters.

In listening to my colleague, there are many potential reasons why intermittent fasting may protect the heart.  Foremost is the effect of intermittent fasting on protecting against diabetes and elevated triglycerides.  However, the most recent research from Ben suggests that other factors might also be involved like the reduction of TMAO which has been associated with coronary artery disease.

6. Restore a Healthy Gut Flora

Increasingly more research is emerging about the importance of maintaining a healthy gut flora and preventing leaky gut syndrome in disease prevention.  Intermittent fasting has been shown to promote a healthy gut flora and may be one additional reason why intermittent fasters enjoy better health.

7. Live a Long and Healthy Life

Many studies in animals show that intermittent fasting may confer the same life preserving effects as caloric restriction.  In addition to the above mentioned mechanisms, it is possible that one additional reason why intermittent fasting may allow for longevity is that intermittent fasting helps to put our bodies into the proper circadian rhythm.

This is certainly one factor we observed during our time in China’s Longevity Village.  These centenarians all had a healthy sleep-wake and feeding natural rhythm.  There is a natural rhythm to life that we need to honor to achieve health and longevity.

Do you intermittently fast?  Intermittent fasting may be as easy as just eliminated that before bed snack.


Disclaimer Policy: This website is intended to give general information and does not provide medical advice. This website does not create a doctor-patient relationship between you and Dr. John Day. If you have a medical problem, immediately contact your healthcare provider. Information on this website is not intended to diagnose or treat any condition. Dr. John Day is not responsible for any losses, damages or claims that may result from your medical decisions.

    • Hi Lawrie,

      Most of the studies looking at intermittent fasting allowed for only water. In these studies anything else was considered breaking the fast.