Intermittent Fasting: Is it Worth Trying?

Throughout the years, there have been many fad diets that people have embraced – the Atkins Diet, the South Beach Diet, and the Zone Diet, to name a few. That list can now include intermittent fasting (IF). Enthusiasts claim it helps with focus, weight loss, and energy.  Support from nutritionists, dieticians, and doctors remains divided for this latest trend.  But what exactly is it, and is it a good choice?

What exactly is IF?

Intermittent fasting is an eating pattern that cycles between periods of eating and fasting. It does not focus on what you eat but rather when you eat it. Throughout human evolution, fasting has been a common practice. Ancient peoples did not have food readily available year-round. There were no supermarkets to buy food from and no refrigerators to store food. They depended on what they could gather or hunt, and sometimes there was no food to be had. As a result, human biology evolved to be able to function without food for extended periods. In fact, research has shown that the human body can survive up to two months without food (depending on the individual).   

Fasting is not a new thing even to more modern societies. Many cultures still fast as a part of their religion. We Greeks fast before our Easter cutting out meats and dairy. Taking this eating pattern and evolving it into a lifestyle choice is not that out of the box. A neuroscientist at Johns Hopkins, Mark Mattson, has studied intermittent fasting for 25 years. He states that our bodies can go without food for several days without issue. Even as little as 50 years ago, we maintained a healthier weight by eating less. Without computers, and with television not available 24 hours as it is now, people went to bed earlier, snacked and ate less, and spent more time playing outside. Without realizing it, we were already fasting.

There are several different ways to do intermittent fasting, but all choose repetitive times to eat and fast. Three of the most popular include the 16/8 Method (also called the Leangains Protocol), the Eat-Stop-Eat method, and the 5:2 Diet. For the first, you eat for only 8 hours in the day and fast for 16 hours. The second, fasting lasts for 24 hours once or twice a week. For the third, you consume only 500 to 600 calories on two non-consecutive days of the week and eat dietary guideline calories for the other five. Of all the versions, the 16/8 Method is the most popular as it is the easiest to maintain.

Effects on the Body

When fasting, your body reacts on a cellular and molecular level. First, your body adjusts hormone levels to make stored body fat more accessible.  Human Growth Hormone (HGH) levels skyrocket as much as five times.  (HGH regulates body composition, muscle growth, and sugar and fat metabolism.) Increasing these levels can result in fat loss and muscle gain. 

Next, your body’s insulin sensitivity improves, and the levels of insulin drop (a lower insulin level makes stored body fat more accessible). In addition, your body initiates a cellular repair process. Old and dysfunctional proteins that build up inside cells are removed and digested, making way for new and healthy proteins. Finally, gene expression, the process by which the information encoded in a gene directs the assembly of protein molecules, occurs in the function of the genes related to longevity and protection against disease. 

Fasting can be a tool used for weight loss and overall health.  It changes the body’s equation between intake and outtake.  Eating fewer calories and burning more stored fat has been proven to have numerous health benefits if done right. 

What Studies Show

Much research has occurred on eating and its effects on the body.  Research done on overweight rats using IF has been promising.  They lose weight, their blood pressure, cholesterol, and blood sugars improve. Unfortunately, these same studies on humans have shown that although IF is safe, it is no more effective for weight loss than any other diet.   Intermittent fasting depends on eating fewer calories overall.  Most humans involved in studies struggled with the fasting part. 

Dr. Deborah Wexler, a metabolic expert (and Director of the Massachusetts General Hospital Diabetes Center and Associate Professor at Harvard Medical School), states that changing the timing of your meals significantly benefits one’s metabolism.  Following a circadian rhythm fasting approach, where meals are restricted to an 8 to 10-hour period in the day with fasting overnight, allows your body to accept and react to the benefits of fasting.  When deprived of food, the appetite hormones and the hunger center in your brain go into overdrive.  Instead of reducing our calories, we tend to eat more.

Research has shown that not all IF approaches are the same.  The most successful and sustainable involve a Mediterranean-style diet.  IF is based on when you eat the food.  What food you eat is equally as important, contrary to the principles of IF.  Just think about it.  If you binge and eat massive amounts of food during your eating periods, you defeat its purpose.

In all research, the most exciting result of IF is its effects on the aging process and reduction in cancer risks.  Dr. Frank Hu, chair of the department of nutrition at the Harvard T.H. Chan School of Public Health, points out that fasting can activate cellular mechanisms that help boost immune function and reduce inflammation associated with chronic diseases.  Research with animals has demonstrated a reduced cancer risk and a slower aging process.

Image: Puwadon Sang-ngern

So Far So Good

With all the studies and articles published revealing the health benefits associated with IF, why aren’t we all doing it?  Let’s take a look at the pros and cons.


  • Weight loss: Intermittent fasting can help you lose weight and belly fat without having to restrict calories as with other diets.  Studies have shown that this eating pattern demonstrated beneficial outcomes for body mass index, body weight, and fat mass in more than 5% of participants.1   
  • Diabetes control: Intermittent fasting can lower blood sugar by 3 to 6% and increase insulin levels by 20 to 31%.  Both of these can help protect against type 2 diabetes.2
  • Reduced oxidative stress and inflammation: Some studies have indicated reductions in markers of oxidative stress and inflammation. Both lead to many chronic diseases.3
  • Heart health: LDL cholesterol, blood triglycerides, and high blood sugar are all risk factors for heart disease.  IF has been shown to improved blood pressure and resting heart rates, reduce bad cholesterol, and increase insulin resistance.  All this results in better heart health. 4
  • Brain and tissue health: With intermittent fasting, the brain hormone BDNF increases.  This increase may aid in the growth of new nerve cells and protect against diseases such as Alzheimer’s.  Studies discovered that the working memory in animals greatly increased and tissue damage in surgery decreased with intermittent fasting.5 6 In addition, autophagy, the body’s way of cleaning out damaged cells to regenerate newer, healthier cells, was improved.7
  • Cancer prevention: Studies have shown that periodic fasting in test animals helped protect normal cells from the toxic effects of chemotherapy drugs.  At the same time, cancer cells sensitize to the treatment.8 Unfortunately, human trials are still inconclusive.
  • Anti-aging effects: Animal studies have indicated an extended lifespan through controlled and intermittent fasting.9
  • Improved physical performance: There have been mixed results regarding the retention of muscle mass or improved endurance with intermittent fasting.  One study indicated that muscle proteolysis (the degradation of muscle proteins) did not increase until after 60 hours of fasting.10 Other studies indicated that mice who fed on alternate days showed better endurance in running.
Image: Cottonbro


  • Possible Eating Disorders: Any diet that supports restrictive eating can trigger some unhealthy food relationships, especially in those who already exhibit signs of an eating disorder.  Some people can take intermittent fasting too far or get caught up in an unhealthy dieting cycle.  Former Twitter CEO and founder, Jack Dorsey, advocates intermittent fasting.  He eats a single meal on weeknights followed by a weekend-long deficit.  Some nutrition experts consider this strict regimen a sign of an eating disorder.
  • Fewer nutrients: Overall nutrition may suffer as the intake of foods is limited.  Unless you are increasing your consumption of vegetables, fruits, lean proteins, and healthy fats, you are consuming less of the nutrients your body needs to keep the metabolism working, reduce inflammation, and a host of other benefits that come from these nutrients.  Most people focus on calorie counts rather than the quality of food.
  • No guarantee for weight loss: One of the side effects of intermittent fasting is hunger.  Feeling starved makes some people prone to binging when they can eat.  Rebound overeating will lead to a long-term increase in body fat even with fasting.
  • Lowered blood sugar levels: Although keeping a low blood sugar level is crucial, long periods of fasting can leave you feeling lightheaded, dizzy, or tired.  You may even experience headaches or nausea.  There is some evidence that intermittent fasting may not be as beneficial for women as for men.  For example, one study showed insulin sensitivity improved in men, but blood sugar control worsened in women.11 Some people may even feel colder as a result of the lower sugar levels.
  • Possible muscle loss: Fasting does not only trigger your body into breaking down stored fat but also carbohydrates.  Under normal circumstances, your body burns a combination of both.  Without consuming carbohydrates for six hours, and the depletion of stored fat, your body begins to convert lean tissue into carbohydrates.   Research shows that preventing muscle mass loss is dependent on a higher intake of protein, especially in women12.
  • It may affect women differently from men: Female bodies are more sensitive to calorie restriction than men. In some women, intermittent fasting can result in irregular or missed periods. A small part of the brain, the hypothalamus, gets disrupted. (It helps release GnRH (gonadotropin-releasing hormone), LH (luteinizing hormone), and FSH (follicle-stimulating hormone)). When the brain cannot communicate with the ovaries, a risk of irregular periods and infertility arises.13 It is important to note that, thus far, only studies on female rats have taken place.
  • Mood swings: Being hangry is a real thing.  Depriving yourself of food increases the levels of cortisol, the body’s stress hormone.  Simply put, our bodies talk to us.  They tell us whether we are hungry or full.  Naturally, we all fast overnight when we sleep.  Fasting outside of that overrides your body’s natural intuition.  Forced fasting can lead to changes in our mental outlook with anxiety, stress, irritability, and even depression.
  • Disruptive sleep patterns: Multiple studies have shown that fasting can decrease the amount of REM sleep achieved. Improved memory, mood, learning, and overall health depend on a healthy REM sleep pattern. If eating too little during the non-fasting period, cortisol levels increase and inhibit your natural ability to fall asleep14.
  • It can make you less aware or alert: Dieticians and doctors argue that intermittent fasting can lead to decreased alertness.  They state that the body does not consume enough calories during the fasting window to provide enough energy for the body. Without this energy, you become less aware or alert.  Think of it like a car.  Without fuel, it can only go so far.
Image: Ella Olsson

When Intermittent Fasting is Not for You

Intermittent fasting is not for everyone – it requires a lot of self-control. Not only do you have to stop eating while fasting, but also not binge when it is time to eat. For those interested in IF, pre-packaged and pre-prepared meals are available to make it easier. Companies like Sunfare in the United States and Ketolibriyum in Canada provide prepared meals for weight loss using intermittent fasting. 

How do you know if you should try it?  First, before starting any diet, you should talk with a doctor, a nutritionist, or a dietician.  You may end up doing your body more harm than good.  Some people should steer clear of intermittent fasting. Children and teens under 18, pregnant or breastfeeding women, and the elderly should avoid IF.  People with diabetes or blood sugar problems are also on this list.  Highly active athletes require more fuel and should also avoid IF.  In addition, those who may have an eating disorder or are prone to eating disorders should not attempt IF.

Signs Intermittent Fasting is Not Working

If you are following any diet, you should never be worried about what you will eat next. Doing so could indicate numerous eating disorders, including orthorexia, an obsession with healthy eating.  Canceling social outings because of eating habits or a preoccupation with your next meal are indicators of this disorder.  You should equally not feel guilty or ashamed if you break your fast by eating too early or too late.  Any anxiety surrounding your eating habits can be a warning sign of an eating disorder.  You should never have any health issues resulting from your diet plan.  For example, you should not be skipping a menstrual cycle or depressed and irritable.  If any health issues are happening, you need to stop IF and talk with a professional immediately.

Image: SHVETS production

What to Do…What to Do?

Just because you have the facts doesn’t mean intermittent fasting is right for you.  It is important to check with a health professional before starting any change to your eating habits.  Most nutrition experts recommend a Mediterranean diet as the blueprint for healthy eating.  Stick with whole grains, leafy greens, fruits, healthy fats, and lean proteins, and you will never go wrong. Let’s face it, everybody loves food, and most of us crave snacks.  If we let our body burn fat between meals and consider a more simplistic form of intermittent fasting (no more snacks while watching TV at night), we may see results without the fancy talk and timeframes.  In reality, there is no one-size-fits-all approach to eating.  We are all different, and we must listen to what our bodies tell us, even while we eat.


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