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What is Intermittent Fasting?

Updated: Mar 7, 2022

Fat II. Watercolor on paper. Discovery Bay, Hong Kong. April 2020.

One of the hottest new nutrition trends in weight loss these days ironically doesn’t actually involve food, but more the timing of your meals.

Wait, isn’t fasting just another word for starving?

Fasting is a traditional practice across multiple cultures that dates back for centuries, often done for religious or health reasons. There are many different forms of fasting: water fast, juice fast, bone broth fast, to name a few.

Fasting is not the same as starving: starving is when you don’t know when or even if you will have the next meal; fasting is when you are voluntarily choosing specific windows of time for food intake.

Intermittent fasting (IF) as a health practice in modern times helps us to reset our insulin and metabolism, as well as detoxify from habits/dependencies (e.g. carbohydrates) that develop over time.

Research suggests that sustained metabolic switching can improve memory, executive function and global cognition.

The principle is simple: You cut way back on stimulating your insulin response for a specified time frame in order to give your body a chance to use up some of your fuel stores in the form of stored up fat. There are many popular fasting regimens include the 5:2 (five days per week of normal eating with two nonconsecutive days of extreme caloric restriction), and the 16:8 (sixteen hours of fasting with an eight hour eating window).

Okay – I’ll admit it.

The urge to use the word “fast” as a marketing pun for this piece was irresistible. Intermittent Fasting is NOT intended to be a quick fix.

Short term diets that involve restrictive regimens of eating over weeks or months,are hard to sustain over time, generally leading to rebound weight gain when we go back to “normal eating” eventually. I also don’t recommend a one-size-fits-all approach to nutrition plans.

Metabolic switching

Intermittent fasting is a long term way of planning your meals where you are choosing when to eat and when not to eat as part of a food protocol that is customized to your body. Turns out that we burn mostly glucose for fuel when our bodies are in a feeding or fed state, but we switch to burning ketones for fuel when we are fasting. Ketones serve not only as fuel, but they are potent signalling molecules that influence the body’s stress response, and impact healthy aging.

Beyond benefits such as weight loss and controlling blood sugar levels, research suggests that sustained metabolic switching regimens with caloric restriction can reduce individual risk of certain cancers, as well as improving memory, executive function and global cognition.

Stephen King said, “Sooner or later, what’s old is new again.” You may view fasting as just another health trend, but this one happens to have centuries of history and tradition behind it, as well as emerging science to back it up.



Please note that our bodies are all different and will respond differently to various eating plans. Dr Em is a doctor, but she is not your doctor. You are advised to seek the guidance of your licensed dietician or doctor before embarking on intermittent fasting if you have diabetes, are taking any medication, are training for an athletic event, have experienced an eating disorder or have any other health issues. Ketosis and dehydration can be dangerous in certain medical conditions.



The Obesity Code by Dr Jason Fung is an excellent summary of the science behind intermittent fasting as an evidence based approach to weight loss and blood sugar management.

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