Why intermittent fasting is all the rage

/

I've hesitated writing about about intermittent fasting (IF) because there is so much information floating around (to date there are more than 8000 scholarly articles if you do a quick google search) and the thought of summarizing the subject has seemed totally overwhelming.

But I was prompted by a friend this past weekend to write about it, so here it goes - a refined, nutshell version based on studies and research done by two prominent voices in the intermittent fasting world: nephrologist Dr. Jason Fung and neuroscientist Dr. Mark Mattson.

Each comes at it from a different perspective - Dr. Fung focuses on weight loss and the role of insulin, while Dr. Mattson is particularly interested in the effects that fasting has on cognitive function, neurodegenerative diseases and longevity.

Lose stubborn weight


As a doctor working with diabetes patients, Dr. Fung saw a direct relationship between insulin and weight gain. In his book, The Obesity Code, he states the following:

I can make you fat.

Actually, I can make anybody fat. How? By prescribing insulin. It won’t matter that you have willpower, or that you exercise. It won’t matter what you choose to eat. You will get fat. It’s simply a matter of enough insulin and enough time.

It was this observation that led Fung to intermittent fasting, as a way to quickly lower insulin in the body. Prolonged periods of low insulin force the body to turn to stored sugar (glycogen) as a fuel source, and when that’s been depleted, to turn to fat.

And burning fat for fuel can lead to weight loss.

Insulin is a driver of obesity


Insulin is known as a fat storing hormone. In laymen's terms, when we eat, our blood sugar goes up, insulin is secreted and signals to our cells (mostly liver and muscle) to take in the blood sugar for energy. Cells will take in as much as they can, and the rest is stored as fat.

Three big contributors to excess insulin production are:
1. What we eat - specifically, too much sugar and simple carbohydrates, which turn into sugar in our bodies (pasta, bread, cereal, refined grains, rice, potatoes, processed foods, etc).
2. When we eat - it could be multiple times a day, where many people nowadays literally eat over the course of 14-15 hours a day (three meals a day and snacking in between, right up to bedtime); or simply snacking on smaller meals throughout the day.
3. How much we eat - fairly self explanatory :)

The point is we never give our body a break, so insulin is always circulating. And over time, our cells can become insulin resistant, leading to pre-diabetes and ultimately diabetes.

This is where intermittent fasting and time restricted feeding (TRF - a form of intermittent fasting where you eat during a set window of time during the day) have been shown to lower circulating insulin in the body, and ultimately achieve weight loss for many. And of course, weight loss can lead to a whole variety of positive changes in the body, including decreased inflammation, decreased triglyceride levels, a decrease in blood pressure and a stronger immune system.

Note that intermittent fasting and time restricted eating are patterns of eating. They are not diets.

So which method do I choose?


There are many variations of both IF and TRF, and it's important to note that everyone's body reacts differently. And it's also important to ease into it - like anything, if change is too dramatic, we often don't stick with it. Here are some variations worth considering:

  • Twelve-hour fasts (TRF): A 12-12 fast is very achievable. If you finish eating at 8pm in the evening, you wouldn't eat breakfast before 8am the next morning. We tend to go through our glycogen stores (stored sugar) in approximately 10-12 hours, and their may be fat utilization for energy during the last two hours.

  • Sixteen-hour fasts (TRF): You may enjoy faster results with a 16-8 IF schedule. Most people choose to consume two meals and a snack (or two) a day within an eight-hour window. For example, you might set your eating window between 12 noon and 8pm, or between 8am and 4pm.

  • 5:2 (IF): This is an eating pattern that involves regular fasting. It means eating normally 5 days/week, and then for 2 non-consecutive days eating only 500 calories. Those two days are where your body will use up its glycogen stores (sugar/energy) and start burning fat for energy.

Two reasons why many people find IF more effective for losing weight than going on a diet are as follows. First, some find IF easier to stick to vs daily restricted eating associated with a diet. Secondly, IF forces our body to go into fat burning mode, whereas one rarely achieves that state if they are simply cutting back on food daily (ie - they will always have stored glycogen to use as energy).

Our brain on IF


Dr. Mark Mattson, a neuroscientist at the National Institute on Aging and a professor of neuroscience at John Hopkins University, says IF is similar to exercise in that it's a necessary stressor for the body. His human controlled studies of IF are wide ranging, including its positive impact on asthma, MS, obesity and most recently (still ongoing), the brain.

To date, animal studies comparing alternate day IF to eating daily, have shown that nerve cells respond positively to the stress of famine. Specifically, certain pathways in the brain are activated, increasing the resistance of the brain cells to more stress, as well as increasing their resistance to age-related neurodegenerative disorders, including parkinsons, alzheimers and strokes (1).

Says Mattson:

  • A major ecological factor that drove the evolution of cognition, namely food scarcity, has been largely eliminated from the day-to-day experiences of modern-day humans and domesticated animals. Continuous availability and consumption of energy-rich food in relatively sedentary modern-day humans negatively impacts the lifetime cognitive trajectories of parents and their children. Mattson 2019

Mattson is in the middle of a human controlled study which he feels strongly will provide a direct link between IF, mental clarity and improved cognitive function.

Other IF / TRF benefits


Many studies have been done highlighting the positive benefits of IF/TRF in the area of autophagy (cell death and regeneration), inflammation and more, but most of these studies have been done on animals. More research needs to be done with humans.

What we do know is that fasting has been going on in most cultures for 1000's of years, and that the studies to date, especially within the area of weight loss, have been very positive. Having said that, just remember, YOU are the expert on how you feel. If you try it out, and it doesn't feel right for you, then don't do it!

Finally, if you are pregnant, suffer from disordered eating, or have adrenal and/or thyroid issues, IF and TRF aren't recommended. And if you have a chronic illness, make sure you check with a medical doctor, naturopath or functional doctor first.

And as always, please don't hesitate to reach out if you want to chat about taking your health to the next level.

Thanks for reading :)

gillian

(1) https://www.ihmc.us/stemtalk/episode007/