Every foodie and fitboy/girl is raving about this new diet, it’s allegedly the answer to all the world’s problems: Intermittent Fasting.

In this guide we'll discuss:

What is Intermittent Fasting?

Intermittent fasting (IF) is simply said, a pattern of eating that doesn’t change what foods you eat, it primarily concentrates on when you eat them. It’s basically an umbrella term comprising a cycle between fasting and non-fasting periods of time.

Although IF recently became trendy, it’s not entirely novel. It all even started by ancient hunter-gatherers that didn’t have supermarkets and freezers, so basically no access to all year-round food. If they couldn’t find anything to eat, they just didn’t eat. As a consequence, humans evolved to operate without food for extended periods of time. [1,2]

Since we now can rely on our beloved refrigerators, freezers and supermarkets, food availability isn’t our main reason to commit to (intermittent) fasting anymore. Currently, IF gained popularity because of a possible relationship found with weight loss and metabolic health improvement. [3,4] Nevertheless, this approach to IF is still found in its early stages and additional clinical research is needed to draw definite conclusions. [5]

However, the outcomes of many small and short-term conducted studies support the existence of health benefits from IF. That’s why we pull out this guide on how to start incorporating IF in your life.

This guide will tell you everything you need to know before trying out an IF diet. We will first dive into the different types of IF. Next, we will tell you the benefits and downsides of this eating pattern. And finally, we will show you how Jimmy Joy can be a helpful companion when committing to an IF diet. Enjoy the ride!

How to do intermittent fasting

As mentioned earlier, IF is a pattern of eating that doesn’t change what foods you eat, but when you eat them. This concept can be implemented in different manners, depending on lifestyle and goals. Buckle up for a little dive into the three main categories of IF approaches!

Modified fasting regimes

The modified fasting regime allows the consumption of 20-25% of energy on scheduled days. An example to do is, is the 5:2 diet, which doctor and journalist Michael Mosley came up with. He dedicated multiple books to this type of fasting, with accompanying recipes and scientific back-up. But how does it work? The name says it all! For five days a week a normal number of calories can be eaten. This amount is restricted to 25% of the normal intake on the other two non-consecutive days, corresponding with a daily intake of approximately 500 calories for women and 600 for men. Despite cutting your energy intake for two days, there is still little evidence considering its effect on weight loss and metabolic changes in comparison to standard energy restriction regimes. [6,7]

Modified fasting regimes

Alternate-day fasting

The approach of alternate-day fasting, focuses on fasting days where no energy-containing food and beverages are consumed. An example of this approach is the Eat stop eat diet. This method is characterized by two non-consecutive fasting days per week, and developed by Brad Pilon during his graduate research on short-term fasting.

The alternate-day fasting approach seems as effective as simple caloric restrictions considering e.g. fasting insulin and glucose concentrations and triglyceride concentrations as shown in animal studies. Besides that, a positive effect on metabolic parameters is shown in human studies, but evidence is limited. Nevertheless, due to self-reported hunger on fasting days which did not decrease over time, this approach is less popular and more difficult to implement than others. [6,8,9]

Time restricted feeding

An easier approach to implement into your lifestyle, is the time restricted feeding approach. Here, days are split up in a window of consumption and fasting intervals ranging from 12 to 20 hours. One way to do so is the 16:8 method, originated from the book 8 Hour Diet by David Zinczenko and Peter Moore who suggest that your body needs fasting periods to process the nutrients you consume. While research is limited, several animal studies have shown a relation with this approach and maintaining optimal metabolic functions. The time restricted feeding compared to the previous approaches has been seen easier to maintain for a longer period, as shown in one of the few studies performed amongst humans. [6,10-12]

Time restricted feeding

What are the benefits of intermittent fasting?

Many promising studies have been done on IF, in both animals and humans. As mentioned earlier it’s still important to understand that some studies have more scientific evidence behind them than others. Since IF is still a pretty new research area, many of the health effects have only been seen in cells or in animals. In humans, IF is safe and considered effective, but no more effective as any other diet. [13]

However, according to some studies, there are some specific benefits that can be attributed to IF, which we will explain in detail up next!

Benefits for prediabetes and insulin resistance

Some studies suggest that there are positive outcomes from prediabetes (people with higher than normal blood sugar level) doing fasting. According to a 2018th study, conducted by E.F Sutton et. al, eTRF (Early Time Restricted Feeding: a unique style of IF where an individual is meant to consume most of their calories in the first few waking hours of the day) improved insulin sensitivity, β cell responsiveness, blood pressure, oxidative stress, and appetite. For this study, eight men with prediabetes were randomized to a 6-hr feeding period, with dinner before 3 p.m. or a control schedule 12-hr feeding period for 5 weeks and later crossed over to the other schedule. [14]

Another study suggested that IF has some major benefits for insulin resistance and can lead to an impressive reduction in blood sugar levels. [15] What this implies, is that IF may be interesting for people who are at risk of developing type 2 diabetes. However, at least for prediabetic men, because a study in women showed that blood sugar control actually worsened after a 22-day long IF protocol. [16]

Reduction of inflammation and oxidative stress

Ever heard of oxidative stress? It’s an imbalance of free radicals and antioxidants in the body, which can lead to cell and tissue damage. It also plays a role in the aging process. [17]

Some studies have shown that IF may enhance the body's resistance to oxidative stress. [18,19] Research amongst 40 healthy volunteers between 20 and 39 years old showed positive results on the inflammatory status of the body and the risk factors for cardiovascular diseases. [20] There were also some studies that suggested that IF could reduce inflammation (the body’s response to injury), which is related to various diseases. [19,21,22]

Reduction of inflammation and oxidative stress

Intermittent fasting for weight loss

IF is seen as a popular strategy for weight loss, which may present independent health benefits. However, according to conducted studies, strong recommendations on IF for weight loss cannot be made at this time. A systematic review of 40 clinical studies found that IF was effective for weight loss, with a typical loss of 7-11 pounds over 10 weeks. Yet, the variability in size of the studies was wide, ranging from 4 to 334 subjects, and followed from 2 to 104 weeks. These studies used different study designs and methods of IF, and the characteristics of the subjects differed (lean vs. obese). Half of the studies were controlled trials which means: comparing the fasting group to a comparison group and/or a control group (either continuous calorie restriction or usual lifestyle), with the other half examining an IF group alone. According to the systematic review IF may reduce body weight and possibly appetite but not other adaptive responses such as brain activity. [23,24]

It can help you live longer?

Some people suggest that IF may improve your lifespan. Wait, what?! Yes, but don’t get your hopes up too high, because these findings were only found in mice. According to a 2018th study published in Cell Metabolism an increased time between meals made male mice healthier overall and live longer compared to mice who ate more frequently. The scientist reported that their health and longevity improved with increased fasting time, regardless of how many calories they consumed or what food the mice ate. These findings are encouraging for future human studies but unfortunately do not necessarily mean that we should all dive into an IF diet straight away. The lifestyle and stress factors one has are not comparable to the ones of an animal under study, which is something that needs to be taken into account. Also, there are some restrictions required to study over a whole lifetime… Once we’re able to travel through time we will hopefully fully know. [25]

live longer through intermittent fasting

What are the downsides of intermittent fasting?

Apart from limited evidence-based research, there may be some other downsides to take in consideration before starting your IF diet. We don’t want to discourage you, but IF is not perfect for everyone and there are some pitfalls with it.

Some studies found that there’s a high dropout rate among intermittent fasters. This may suggest that it might not be a sustainable approach. Another downside may be that it could have its negative effects on your social life… For example when your friends are having dinner at 7 and you’re not allowed to eat anymore after 6, you’ll just have to sit there and drool at their plates. According to Dr. Seltzer (MD, weight-loss physician and certified personal trainer) IF may also increase the urge of binge-eating behavior. “Not eating for 16 hours could make you feel extremely hungry. Because of this you’re more likely to go way over your daily calorie amount,” Dr. Seltzer explains. According to Alissa Rumsey (RD, a NYC-based dietitian), IF can also lead to an unhealthy obsession with food for some people. “Since people are only allowing themselves to eat in a certain window of time, they are completely ignoring their internal cues of hunger.” [26]

Another potential downside may be digestion problems. Eating large amounts of food in a short period of time can lead to digestion problems, because lager volumes of food need more time to digest. This can cause additional stress on your digestive tract, leading to indigestion and bloating. This is why IF is not recommended to people that experience digestive issues or suffer from IBS (Irritable Bowel Syndrome). People suffering from these issues are recommended to obtain regular bowel functions by eating at regular times and not skip meals. [27]

Should I give intermittent fasting a try?

As stated before, IF is not for everyone. If you're considering IF, make sure to first discuss this with your doctor. Avoiding meals and limiting calories can be dangerous for people with certain conditions, such as diabetes. Anyone with a history of disordered eating, women who are pregnant or teenagers and children should not consider this. People who take medications for blood pressure or heart disease also may be more prone to face problems from fasting. [28]

According to Dr. Stephen Freedland, associate professor of urology and pathology at the Duke University Medical Center, there also remains debate about whether the actual fasting is responsible for the health benefits, or if it’s simply the reduction of calories. If the health benefits can be attributed to calorie reduction, it’s probably wiser to start reducing your overall calorie intake, before ‘torturing’ yourself by fasting. [29]

In the end, the most important thing is to develop a healthy eating pattern that is sustainable and can support a healthy weight over time. As of now, intermittent dieting has not been proved to meet this key criterion according to Kathy McManus, director of the Department of Nutrition at Harvard-affiliated Brigham and Women's Hospital. But of course, every individual is different, so we leave this up to you. [30]

How can Jimmy Joy help with intermittent fasting?

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Complete Guide to Intermittent Fasting

What is Intermittent Fasting?