The Science behind how we store, use and utilise food

This is a lengthy blog post, but well worth a read for those of you who are interested in the 'why' you should fast, just as much as the 'how'.

Food is more than an energy source and fasting is more than simply going hungry. Unprocessed foods (‘wholefoods’) nourish our body and mind, deliver energy, and support our digestive and endocrine (hormonal) systems, among others. 

But we consume too much processed food laden with chemicals, preservatives and fillers, and it is - quite literally - killing us. When we eat carbohydrates (and most people eat more than they need to), the pancreas secretes insulin, the ‘storage hormone’, which helps maintain blood glucose levels. 

Insulin’s job is to drive blood glucose (sugar) from our blood into our muscles, fat cells and liver for storage. When we consume carbs in quantities that reflect our energy needs, insulin can do its job, but when we eat too much (so much that it can’t be utilised or stored in our muscles) it’s stored as fat. 

The higher your blood glucose levels, the more insulin is needed to help lower it. But resistance to insulin can build, especially when blood glucose levels are elevated too often, for too long. Insulin resistance is when cells in your muscles, fat, and liver don’t respond well to insulin, which causes blood glucose levels to elevate, eventually leading to pre-diabetes, and if uncontrolled, to diabetes and then diabetes-related complications.

Chronically high levels of blood glucose as a result of poorly-controlled diabetes can contribute to heart disease, diabetic retinopathy (a form of diabetic eye disease that can lead to blindness), nephropathy (kidney disease), and neuropathy (a nerve disorder).
It’s important to understand that injected insulin is absolutely necessary for controlling type-1 diabetes, since your body cannot supply its own, but type-2 diabetes can be prevented, controlled and reversed with proper diet and lifestyle; the latter two under medical supervision.

Not all carbohydrates work the same in the body. Highly-processed foods and ‘simple carbs’ like those found in sweets, sodas and even naturally in fruits, trigger a fast ‘spike’ in blood glucose, while others result in a slow and sustained blood glucose (and therefore, insulin) response.

The glycaemic index (GI) addresses these differences by assigning a number to foods that reflects how quickly they increase blood glucose compared to pure glucose (sugar). The GI scale goes from 0 to 100, where pure glucose has the highest GI and is given a value of 100.


Eating low-GI foods can minimise peaks in blood glucose and the insulin response and supports weight-loss and healthy weight. Frequent snacking (especially when these snacks are high-GI and carb-heavy) results in insulin secretion and glucose being stored as fat. Fasting elicits no insulin response, and therefore not only improves your body’s ability to use glucose more effectively, but allows you to tap into stored fat for fuel.


Additionally, glucagon and growth hormone are also increased during fasting. Glucagon is the fat burning hormone, while the growth hormone helps the body repair and grow. Now that glucose isn’t available in the body, it begins tapping into stored fat for fuel. As you increase the duration of your fasts (i.e., the time between meals), your body uses fat and ketones rather than glucose (sugar) as its main fuel source (known as being in a state of ketosis). But this only happens once glycogen stores are depleted.

Fasting for at least 14-hours will get most people into a state of ketosis, especially when coupled with a diet lower in carbohydrates, and rich in fibre, good fats and protein.

If appropriate for you, once you have built-up to responsibly applying prolonged fasting techniques (for periods of 24 to 72-hours), autophagy (the body’s process of replacing old or damaged parts of cells), begins to take place along with anti-aging benefits and increased energy producing capabilities as the body begins to tap into stored fat as energy and repair itself thanks to higher levels of human growth hormone.

From a very young age, we are programmed to have breakfast first thing in the morning, lunch around 12-1pm, and dinner at 7pm. Ghrelin, our hunger hormone (and another storage hormone) increases just before meal and snack-times, cueing us to eat. Have you noticed that your stomach always knows when it’s lunch time?

But, is eating 3 meals and 2 snacks a day really best for you? There is a lot of evidence to suggest this may not be the best approach. In fact, eating 2 meals instead of 6 has been shown to improve metabolism in people with diabetes.

Further, Diabetes UK estimates that around 5 million people will have diabetes by 2025, and it’s easy to see why, with so many of us making poor or misdirected lifestyle choices leading to weight gain year-on-year.

If you'd like to learn more about fasting, which type of fasting method is best for you and how to fast correctly, check out The Fasting Playbook for more.