The intermittent fasting benefits may be is something you have heard others discussing, read about online, or seen in a TV segment. Becoming an increasingly popular way to lose weight and lead a healthy lifestyle, intermittent fasting has gained traction due to it being more of an eating pattern than an actual diet. No cutting out specific foods or counting calories necessary. Instead of changing what you eat, you change when you eat.
But, still wondering exactly what intermittent fasting is?
Intermittent fasting is an umbrella term for a variety of diets that cycle between fasting and non-fasting. Some of these diets will also include calorie restriction during the eating periods for weight loss. Intermittent fasting diets can be broken into three categories: alternate day fasting, whole day fasting, and time-restricted feeding.
Alternate day fasting is exactly what it sounds like: one day you fast, the next day you eat a normal diet. There are two variations of this diet. In first version, called alternative day modified fasting (ADMF), you are allowed to consume 500-600 calories on your fast days, plus as many calorie-free drinks as you would like. In the second version, fast days are true fasts. This means that every other day you are restricted to only consuming calorie-free beverages such as water, coffee (black coffee that is) or tea. Several studies have examined the effectiveness of ADMF for weight loss. A study conducted by the University of Illinois-Chicago showed that participants found it easier to stick to the every other day fasting diet than a typical caloric restriction diet. They also found that participants adapted quickly to intermittent fasting and that hunger on the fast days decreased by the 2nd week, even when exercise (about of 6500 steps per day) was maintained on fasting days.
A variation on alternate day modified fasting is whole day fasting. In this variation, also known as the 5:2 diet, a normal number of calories is consumed five days a week and then, for two, non-consecutive days, only 25% of usual caloric intake is consumed. This comes out to be about 500 calories for women and 600 calories for men. It’s not a full-on fast, but it sends your body into a similar starvation mode. On days you aren’t fasting you stick to a healthy diet, containing the same number of that you’d typically consume. This diet has become extremely popular in Britain and is overall one of the most popular of the fasting diets.
Time restricted feeding is restricting food consumption to a limited number of hours per day. Typical fasting periods are anywhere from 12 to 18 hours, leaving a 6-12 hour window for eating. This often looks like only eating between the hours of 8am and 6pm. Studies have found that when limiting the number of hours for food consumption, people typically eat fewer calories.
The different styles all have a similar goal in mind: restricting calories on certain days or during certain hours. The motivators for adopting this style of eating include weight loss, plus a myriad of other health benefits.
Weight loss is the number one reason people turn to intermittent fasting. It’s a unique take on calorie restriction; instead of restricting your calories every single day, you restrict on certain days or for certain hours of the day. It’s a simple concept that eliminates the need to constantly keep track of everything you consume.
So what does the research say? Several studies have shown that weight loss is likely with intermittent fasting. The University of Illinois-Chicago study found that people who maintained an intermittent fasting diet for 6 month experienced a weight loss of 3-8%. Calorie consumption was lower and weight loss was higher when participants did alternate day fasting versus time restricted feeding. Alternate day fasting led to a 1.5 lb weight loss per week, whereas the time restricted feeding variation only resulted in a 0.5 lb loss per week.
Another study done by Stanford University found that intermittent fasting plus restriction of total calories helped obese women successfully lose weight. The take home message here is that while for some individuals, following some form of intermittent fasting will allow them to naturally eat less, for others, intermittant fasting can provide the structure needed to more successfully follow a low-calorie diet.
On top of being a potentially superior way to reduce caloric intake, a study done by the University of Vienna found that after fasting for 30 to 60 hours, participants’ basal metabolic rate increased. Why does this matter? Your basal metabolic rate is the number calories needed to keep your body functioning while at rest. With a higher metabolic rate, you burn more calories while at rest, which typically leads to weight loss. They also found that fat metabolism increased, meaning that participants burned more fat than muscle during fasting. However, it is important to remember that you do not need to fast for over 24 hours to experience metabolic benefits from intermittent fasting.
One area that researchers have studied extensively is the impact of fasting on your hormones. There are several positive effects that have already been discovered. First, intermittent fasting has been found to increase the production of the human growth hormone (HGH). A study done by the University of Virginia School of Medicine found that men typically produce HGH at highly varied times. When fasting, men produced HGH at more regular intervals. HGH is important as it helps to promote fat loss and increases muscle mass. It also helps to increase cardiovascular fitness.
Insulin is another hormone that was impacted by intermittent fasting. A study conducted by the Pennington Biomedical Research Center found that alternate day fasting led to reduced insulin levels. The participants fasted every other day for 22 days. By the end of the time period, researchers found that fasting insulin levels had decreased. Lower insulin levels allow your body to burn more fat. Insulin sensitivity also improved. This is important because if we become less sensitive to insulin, we are more likely to be at risk for diabetes. If we aren’t that sensitive to insulin, our bodies need to produce more to maintain blood sugar levels. Pushed to its limits, the pancreas at some point will no longer be able to produce insulin properly, and that’s when diabetes occurs. Keeping our insulin sensitivity high is an important factor in warding off diabetes.
For those who are already at risk for type 2 diabetes, intermittent fasting can improve your risk factors. The research done by the University of Illinois-Chicago found that participants on the intermittent fasting diet saw a 3-6% reduction in fasting blood sugar levels while fasting insulin dropped by as much as 31% in some participants. Reducing blood sugar levels and improving insulin sensitivity are two major factors in reducing the overall risk for type 2 diabetes.
We’d all like to stay younger for longer and intermittent fasting may help with that. In a study by The Scripps Research Institute in La Jolla CA, short term fasting was shown to increase autophagy. Autophagy is the process by which cells digest and remove old and dysfunctional proteins that build up inside them. It’s essentially your body’s way of cleaning house and then recycling or disposing of what is damaged or worn-out. Autophagy can help make our bodies more efficient by ridding it of faulty cells or undesirable clutter. Autophagy is brought on by stress, and intermittent fasting or exercise can provide the stimulation the body needs to get the process rolling. This process can help to prevent autoimmune disease, heart disease, and even cancer. Fasting is a way this process can be induced, which can provide some long term health benefits.
The Institute of Aging studied intermittent fasting in rats and found that 83% of rats that were on the fasting diet lived longer than those that were not.
There is also clear evidence that fasting can help prevent aging of our brains, and even Alzheimer’s. Research by the Department of Neuroscience at John Hopkins University has shown that fasting can help prolong the health of the nervous system. The nervous system is extremely vulnerable to advancing age and when impacted can lead to Alzheimer’s or Parkinson’s Disease. Their study found that intermittent fasting impedes upon the metabolism and cellular stress response systems in a way that protects the body from environmental and genetic factors to which they’d otherwise succumb during aging.
There is some promising research being done with mice and rats that shows that intermittent fasting may help prevent cancer. A study completed by the Université de Grenoble in France found that middle aged mice that were kept on an alternate day fasting diet saw lower rates of lymphoma than those that were not. The Mount Sinai Hospital Center in Chicago also did an interesting study on the impacts of alternate day fasting on tumor bearing rats. Half of the tumor-bearing rats were fed every other day, while the other half were allowed to eat freely. They found that the alternate day fasting group experienced an increase in survival. Their conclusions were that dietary restrictions could help to slow the progress of cancer and improve survival of human cancer patients.
The metabolic effects of fasting may also be part of the key in the prevention or slowing of cancer. The Feinberg School of Medicine at Northwestern University found that sirtuins, a class of proteins that impact a wide range of cellular processes like aging and inflammation, may have anticancer effects. They believe that sirtuins can be activated by fasting, which then allows these proteins to impact the body’s insulin response and antioxidant defense system. Sirtuins involvement in metabolic regulation allows them to shift the metabolism to different cells, reducing the proliferation of cancer cells.
Intermittent fasting may also improve cancer treatments. Multiple studies have shown that fasting while undergoing chemotherapy treatment can improve results. A study by UCLA found that short term fasting can increase the number of normal cells being produced in chemotherapy patients. They also found that patients had fewer side effects or a reduction in those side effects from chemotherapy when they fasted.
Another study done by the Norris Cancer Center at the University of Southern California found that fasting slowed the growth of cancer cells as well as increased the sensitivity of certain cancer cells (breast and melanoma) to chemotherapy treatment. The tests were run on mice, so further reasearch is needed to confirm that these results would also apply to humans, but this study found that the combination of intermittent fasting plus chemotherapy resulted in long term cancer-free survival.
Early animal research studies show that intermittent fasting could have very positive effects on the brain. As mentioned previously, intermittent fasting improves many metabolic features including improving of insulin sensitivity, reduction in blood sugar, reduction in inflammation and oxidative stress, all of which positively impact our brains. On top of that, a study from the National Institute on Aging found that in rats, intermittent fasting actually increased in the number of newly generated neural cells.
Researchers at the Institute for Neurosciences in Baltimore discovered that intermittent fasting can protect the brain during a stroke. Research done on mice showed that mortality, brain damage, and functionality impairment were all reduced in mice on an intermittent fasting diet. These are again all early studies, but very positive signs that intermittent fasting can have positive impacts throughout our bodies and help to protect our bodies.
Heart health is one of the most important health related issues facing most of us. Heart disease is the number one killer and comes in many forms from heart attacks to heart failures to strokes. Any and all opportunities to reduce our risk factors are worth considering. The study done by the University of Chicago found that LDL, triglycerides, and total cholesterol were reduced after 8 weeks on an alternate day fasting diet. Systolic blood pressure of the participants also dropped in that time period.
A study on rodents conducted by the Faculty of Health and Medical Sciences at the University of Surrey in the UK found that alternate day fasting over a 2 year period led to protection from ischaemic injury and reduced the likelihood of heart failure. The researchers found that overall cardiovascular health was improved by an intermittent fasting diet.
While much of the research is early, there are many positive signs that an intermittent fasting diet can improve your short-term and long-term health. But, it is important to note it might not be for everyone. Some people can’t tolerate the extended periods without food and another approach to weight loss may be better. Individuals with certain medical conditions (hypoglycemia, history of eating disorders) should talk to a doctor or refrain from fasting. There is also some concerns about potential harmful effects on hormones in women of childbearing age. Like with any new major diet shift, it is important to evaluate it is right for you.
From aiding in weight loss to improving insulin sensitivity, intermittent fasting can help improve some of our more obvious and immediate health problems. There are also strong potential health gains to be made in the slowing of aging, improvement of heart health and prevention of cancer. While intermittent fasting could easily be dismissed as the newest diet fad, it does, in fact, have a strong basis in science and research. There are great reasons everyone’s talking about it, as it could be a key to improving our overall health.