Research-Based Information on Intermittent Fasting
Intermittent fasting has started to get more and more attention for both its positive effects on weight loss and other health benefits. Some might think of this as a fad diet, but there is a lot of research and physiological backing behind fasting.
The purpose of this article is to go through the research and talk about the findings, discuss the different ways to fast, debunk some of the myths, and then discuss helpful hints on how to incorporate these changes into your lifestyle.
What We Know About Intermittent Fasting and Calorie Restriction
There are benefits to calorie restriction that cannot be denied. Undisputed research has shown that caloric restriction dramatically improves metabolic health, many important markers of health, and longevity of life.
It is important to realize that the research deciphers between two different kinds of energy deprivation:
1. Caloric restriction (CR). This is decreasing the amount of calories consumed in general.
2. Total caloric desistance (TCD). Total caloric desistance comes in many different forms including intermittent fasting, alternate-day fasting, routine periodic fasting, or intermittent energy restriction. For the purpose of this article, I will call use the term intermittent fasting as a broad term to describe this category.
In a nutshell, calorie restriction is the broad term, and intermittent fasting is how we can truly incorporate fasting into our lives. Intermittent fasting can be achieved in various ways; either by eliminating or significantly reducing calories for a few hours everyday, fasting for 1-3 days every week, or fasting intermittently throughout the year.
Want to know more about specific techniques for intermittent fasting? 5 Intermittent Fasting Methods
In 2015, a comprehensive review of research published in The American Journal of Clinical Nutrition showed positive results of fasting and calorie restriction. The more that we eat, the more we demand out of our bodies. Whenever we eat, we create more free radicals and oxidative stress that breaks down cells, DNA, and puts more wear and tear on the body as a whole. Studies indicate that short-term fasting can increase longevity, help regulate glucose levels, and help treat everything from asthma and autoimmune diseases to cardiac arrhythmias.
Therefore, research shows that there is one guaranteed way to live longer… eat fewer calories throughout your life.
What are the research-based benefits of fasting and intermittent caloric restriction?
1. The body uses fats for energy during intermittent fasting
2. Results in cellular-level repairs, functional optimization, and metabolic rejuvenation
3. Long-term health benefits including reduced cardiovascular risk factors and atherosclerosis
4. Helps support healthy glucose metabolism
5. Improves cognitive function
Why is intermittent fasting so powerful for weight loss?
It is as simple as hormone control.
Insulin has two main jobs.
1. To take blood sugar out of the blood and push into the cell for energy production.
2. To manage the storage of fat for energy reserves.
Eating too much not only increases insulin but also IGF-1, insulin growth factor. We utilize IGF-1 and insulin to regulate crucial functions in our body that are responsible for growth. However, too much of these hormones cause various long-term problems. If we produce too much, or it is not regulated properly, then it can lead to accelerated aging, the breakdown of cells in the body, and even cancer.
If you are constantly eating throughout the day, then you are constantly feeding your stress hormones, cortisol from the adrenal glands. If you fast and take breaks from eating, then you “starve” your adrenals during that time. This can cause your body to release fewer stress hormones and instead focus on repairing and rejuvenating the body. Moreover, less cortisol means better weight management especially for visceral fat (fat around the middle).
Research backs up that the body sheds fat during times of fasting. Small human studies revealed a weight loss of 2.5–8% after 3–8 weeks of alternate-day fasting. In a larger 3-month study, weight was 6.3% lower after taking a twice-weekly approach to fasting.
Therefore, by fasting, one manages his or her insulin, IGF-1, and cortisol. By decreasing the output of these hormones, many health benefits are achieved, even beyond just weight loss.
It is not just about food quantity but also about food quality.
By regulating the different hormones with how we eat, we change the way that our body is being signaled by food.
We have also learned that we activate a longevity gene by intermittent fasting. This gene is there to help us through times when food is not as readily available. Clearly we needed this gene in the past, but not as much in a time when we are overfed and undernourished. But we can tap into this innate wisdom of the body by eating less and eating more nutrient dense foods through intermittent fasting.
Taking a Closer Look at the Research
One of the many people responsible for studying intermittent fasting is Krista Varady, Ph.D., an associate professor of kinesiology and nutrition at the University of Illinois at Chicago. She has published about 20 different studies on alternate-day fasting and is currently completing a one-year study funded by the National Institutes of Health on alternate-day fasting.
Varady’s research demonstrates that there are many benefits to intermittent fasting. One of her recent studies published in the November 2013 issue of Nutrition Journal randomly divided 32 subjects into two groups. One group practiced alternate-day fasting for 12 weeks, while the control group ate normally. Varady found that those in the alternate-day fasting group lost approximately 1 pound per week, experienced cardioprotective effects, and saw a triglyceride concentration decrease of 20% with positive improvements in LDL particle size (which decreases the risk of coronary heart disease).
In her research, Varady also found that alternate-day fasting seemed to help lower diabetes risk. A review of 12 animal and three human trials she published in the July 2007 issue of the American Journal of Clinical Nutrition found a lower diabetes incidence and reduced fasting blood glucose and insulin concentrations in those following alternate-day fasting diets.
Important metabolic and cardiovascular benefits have been reported in humans that deserve further consideration in therapeutic fasting trials, such as decreases in fat mass, LDL- cholesterol particle size, LDL cholesterol, triglycerides, and C-reactive protein.
Why are athletes utilizing different types of intermittent fasting?
Krista Varady also found with her research that fasting did NOT lower participants’ resting metabolic rate like many people would think that it would. A matter of fact, she found that lean tissue was preserved, and better metabolic rates were achieved through fasting. With most diets, 75% of what people lose is fat, and 25% is muscle. According to a study published in Metabolism in January 2013 and a study in American Journal of Clinical Nutrition from November 2009, with alternate-day fasting, the loss comes from a more favorable 90% fat and 10% muscle. That is why it doesn’t change your metabolic resting rate and is beneficial for overall body composition. And the reason for this is due to its effect on Human Growth Hormone. Research has shown that fasting increases Human Growth Hormone (HGH) that facilitates the repair of tissue, fat breakdown, and fatty acid release during fasting as energy.
As we age, HGH levels naturally decrease. HGH deficiency in adults will lead to an increase in body fat, lower lean body mass and a decrease in bone health and mass. Therefore, to naturally be able to cause surges in HGH on fasting days has many health benefits. This dramatic increase in the effect of HGH does only seem to occur while fasting and goes back to normal after normal feeding resumes.
This benefit is huge for everyone because it means that fasting will cause a decrease in body fat while preserving lean mass through the increase in HGH. This is why we see such a benefit and many intermittent fasting plans focus on utilizing it with elite athletes.
Let’s look a little closer at a few of the concerns people have with fasting.
But don’t we want to eat small frequent meals?
We have been told for years to eat frequently. We given the guidance that “it is best to eat small meals throughout the day; one should shoot for 6-7 meals a day.” Even though this can have some benefits on “keeping up your metabolism,” it can have severe metabolic consequence, especially for individuals with metabolic concerns.
If you are constantly fed, then you are constantly asking insulin to control sugar levels in the blood and cell. You are also constantly feeding the adrenal glands, which can lead to more cortisol production and weight gain. You are also causing constant oxidative stress (free radical production) that leads to accelerated aging and more wear and tear on the body.
It must be said that constantly grazing interferes with metabolic processes. It demands more out of the body and puts much more stress on having the body normalize blood sugar, breakdown food, and regulate energy.
See how this is a more complicated balance than we were originally led to believe.
Why is it important for us to control oxidative stress in our body?
Also, remember that we were not made to have to eat the same amount of foods and at the same time everyday. This would not make sense at all from a survival mechanism of how we were engineered to eat back in the day.
We are all jumping on the Paleo Diet bandwagon to eat the foods that our ancestors ate (even though our food sources have changed drastically), but we have yet to incorporate HOW they ate. Which might be more important! And truly our paleo ancestors intermittently fasted as part of their way of living.
It seems that you only lose weight because you restrict calories.
The majority of research on intermittent fasting is on weight loss. Time and time again it is shown that it is a great tool for fat burning. It has a positive effect on insulin levels and cortisol levels. By controlling these hormones, somebody can easily utilize insulin, and therefore go into a fat burning state.
Because of the positive effects that we have seen in body composition with fasting then the results are more than just due to calorie restriction. Also, it has been shown that individuals that incorporate fasting eat fewer calories even on the days they don’t fast (about 10% on average) less than those that don’t incorporate intermittent fasting. Therefore, the benefits come from much more than just fewer calories on the days you fast.
What about cravings?
Clinically, I have noticed this is the hardest component of incorporating any intermittent fasting into your life. The truth is, though, that most cravings come from the type of foods that you are eating and not genuine hunger.
We now know through research that cravings stem from any overactive opioid response in the brain. Certain foods cause certain people’s brains to become addicted to these foods due to the increase in opioids. These opioids increase pleasure and lead to the roller coaster of cravings/addiction. Besides this physiological reason for food cravings, they often have a connection to emotion and desire.
Therefore, the best way to cut out cravings is to cut out these foods completely. You can’t be addicted to gambling and still go to the casino. You can’t be addicted to drinking and still go to the bar. And you can’t have this addictive response in the brain and still dabble with the foods causing the cravings. YOU MUST CUT THEM OUT COMPLETELY.
And usually, the foods that cause the most cravings are carbohydrates. Therefore, it can extremely beneficial to start by drastically decreasing your carb intake and then gradually add in intermittent fasting after the cravings have been controlled.
Or start with a more ketogenic diet to get carbs and sugars out of the diet and then utilize intermittent fasting.
However, I find that cravings need to be respected. And there are things that can be taken to help control these cravings. I find that 5-HTP based supplements can be extremely beneficial because they increase serotonin levels to help combat the brain response to eliminating these foods.
Overall, the research and physiological rationale behind intermittent fasting shows the many positive effects that it can have on both weight management and overall health and longevity. It is important to incorporate a method of fasting that works for you.
Article and Research By Dr. Meaghan Kirschling, DC, APRN, RN, MS
