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“Fast” Hack for Weight Loss

Updated: Jan 14, 2023

Adipose cells I. Watercolor on paper. Discovery Bay, Hong Kong. April 2020.

One of the most effective new nutrition trends in weight loss these days ironically doesn’t actually involve food choices, but instead it targets the timing of your meals.

Wait - you want me to starve?

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 your next meal; fasting is when you are voluntarily cutting back on eating by controlling the timing of your 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. carbs) that develop over time. Other health benefits may include boosting memory function, reduced inflammation, delayed aging and cancer prevention.

Fasting is when you are voluntarily cutting back on eating by fixing the timing of your intake

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 the stored up fat. Some popular fasting regimens include the 5-and-2 (5 days normal/2 days extreme restriction), and the 16:8 (16 hours of fasting and 8 hours eating window).

How does it work?

One of the key goals of intermittent fasting (IF) is to reduce insulin levels. Insulin is the key hormone produced by your body when digesting food – it works to store excess fuel in the body. So, if we can reduce the levels of insulin by fasting we can allow the body to consume some of that excess fuel (i.e. fat).

By minimizing insulin stimulus, we are allowing our bodies to burn more fat rather than sugar. Most of our bodies have become very efficient at consuming carbs to produce sugar as energy. When we fast, we are retraining our bodies to consume fat to produce ketones are energy instead.

Photo by Rod Long on Unsplash

If you think about it, human beings probably had long periods with little or nothing to eat during the millennia that our ancestors lived as hunter-gatherers – the concept of having an abundance of food with regular meals and frequent snacks only came about in recent decades.

The problem is that we have taught our bodies to become dependent on always having easy access to a constant supply of nutrients, so there is no opportunity to burn off those fat stores that we are all carrying around with us everywhere. I find it’s helpful to draw an analogy with having your freezer packed full of frozen food but instead of using that food, you keep getting take-away food delivered.

There is no opportunity to burn off those fat stores that we are all carrying around with us everywhere

Of course it takes more time and effort to thaw or prepare the frozen food, and ordering DoorDash is much quicker and easier, but eventually your body gets lazy and forgets how to access those fat stores. In fact, it tends to accumulate more and more freezers (fat cells) to store the extra food when we don’t finish all the food.

In this analogy when we fast, we quit ordering online food deliveries and instead we force our bodies to go to the freezer, to learn how to “dine in” again. Over time, our bodies get more and more used to accessing fat stores efficiently, and may even prefer that form of fuel.

Flavours of hunger

Hunger signals in the body can sometimes represent actual physical hunger, like when you haven’t eaten for more than 5-6 hours, but it can also signal a number of other needs.

Have you ever experienced hungry signals like that hollow ache or growling sensation inside, but then it’s not mealtime or maybe you just ate a couple of hours ago? This used to happen to me all the time and it turned out to be one of two flavours of hunger: either I was feeling an urge to eat caused by stress, or I was actually experiencing sugar or carb craving.

Photo by Oladimeji Ajegbile on Unsplash

I had always thought of myself as an even keeled person who was good at controlling emotions. And separately, that I just loved food and snacks, and felt hungry all the time. Until I learned to connect the dots between stress and my using food as my coping mechanism. We all have our vices, right? Could be alcohol, smoking, gaming, shopping, to name just a few. Some are more socially acceptable or obvious than others, but what these coping mechanisms have in common is that they offer us a form of temporary escape or relief from stress.

Hunger can represent an urge to eat caused by stress, or a sugar/carbohydrate craving

I would experience sugar/carb withdrawal as an extremely intense form of voracious hunger that often had an emotional component, also known as “hangry.” This was such a common experience within the family that we used to joke that “hangriness” was a genetic trait. But actually it’s incredibly common, because processed carbohydrate foods are so ubiquitous, and the food industry has gotten so good at manufacturing sugary drinks and foods that light up our dopamine driven pleasure buttons.

Fat fasting

Our obesity and diabetes epidemics in developed countries can be traced back to our physiology which is being overstimulated by highly processed sugar/carbs, triggering repeated bursts of dopamine that drive the addiction cycle. The principle behind intermittent fasting is to break the cycle of addiction to carbohydrates. Insulin levels spike in response to high carbohydrate intake, but when those levels fall off we end up craving more carbs which in turn leads to a vicious cycle and eventually insulin resistance.

While there are many approaches to intermittent fasting (IF), I have found that “fat fasting” is a good way to ease into it. This is where we are teaching our bodies to use fat as a fuel, i.e. “dining in” on the frozen foods stored in our freezers. I found this was most effective when I was able to minimize intake of sugars and starchy carbohydrates, especially processed varieties. As I became more “fat-adapted” (aka burning fat for fuel instead of sugar) I also became less ravenously hungry.

When you get hungry during a stretch of “fat fasting”, first ask yourself if it’s been more than 5-6hrs since you last ate. Could you be dehydrated? Or are you feeling the urge to eat because of something that’s stressing you out?

If you’ve determined that you are legitimately physically hungry, reach for a “fat snack”, like 1-2oz of nuts. Brazil nuts are my favourite because they are filling, and they honestly don’t taste that great, so you’re unlikely to overeat them. Other options include half an avocado, one whole hard-boiled egg, 1-2 oz cheese, or peanut butter (ingredients label should ONLY read peanuts and salt).

Photo by Raspopova Marina on Unsplash

Our bodies tend to do best with gradual adaptation to fasting, slowly extending the fasting time from 8 to 10 hours, then 12 to 15 hours, and so on. Dehydration and salt deficits are common early pitfalls, so be sure to track your fluid intake: make sure you are consuming at least 6-8oz of water every 2 hours, ideally with ⅛-¼ tsp salt.

Okay – I’ll admit it. The urge to use the word “fast” as a pun in the title of this piece was irresistible. Intermittent fasting (IF) is NOT intended to be a quick fix and I don’t believe in short term “diets”. IF is a long term way of eating where you are choosing when to eat as part of a food protocol that is customized to your body.


Please note that this article is intended for education and/or entertainment purposes. Dr Em is a doctor, but she is not your doctor. Our bodies are all different and will respond differently to various eating plans. If you have diabetes, or if you are on medication, guidance should be sought from a licensed dietician or doctor.



Excellent summary of the science behind intermittent fasting as an evidence based approach to weight loss and blood sugar management.

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