What’s the Deal with Intermittent Fasting?
It’s the new thing!
Everybody is doing it!
It’s so easy!
I feel great!
These are some of the comments I hear about intermittent fasting. And, undoubtedly, people are sincere in their approval of this way of eating. Admittedly, there are a lot of benefits to intermittent fasting (IF), some of which I am experiencing right now as I write this blog - an improved ability to focus and mental clarity!
That’s right, IF (also known as time-restricted eating or TRE) is not just about losing weight. In fact, some of the other benefits are so exciting that losing weight often becomes an added bonus! Let’s look at what happens in our bodies when we don’t eat for an extended period of time.
Around 7pm, we eat our last meal for the day and the glucose in the food triggers insulin to be released from our pancreas. (Foods that contain more glucose are sugar and simple carbs; fats and proteins have less glucose, so require less insulin). The insulin interacts with the glucose so the cells in our body can use the glucose for energy. When those cells are fully fueled, the rest of the glucose is stored. First, some is stored in the liver and muscles as glycogen. When those storage areas are full, the rest is stored as fat in our fat cells.
Within four to twelve hours after our last bite of food, the glucose is cleared and is no longer available for fuel, so the body begins to use the glycogen stores for energy. If we eat again before twelve hours, we are not working to deplete the glycogen stores and so don’t enter a fasted state. Once the glycogen stores are depleted (the timing of this varies, depending on what you have eaten and how much glycogen is stored), the body turns to the fat stores for energy. This fuel is typically in the form of triglycerides (a fat), which is fine for most of the body. However, the brain cannot use triglycerides for fuel so our livers convert the fat to ketones which are able cross the blood-brain barrier and fuel the brain.
While all of that is interesting, it still doesn’t really explain how fasting leads to actual health benefits. So, let’s take a look at what happens in our brains when they are fueled by ketones, and in our bodies when they are fueled by triglycerides.
First, the brain. Increased ketones in the brain coincides with the activation of enzymes that increase autophagy, which is the repair and recycling of damaged cells. This means that we have more healthy brain cells to work with when we fast! Additionally, ketones improve plasticity in the brain, which is the growth and repair of neurons (the things that send signals throughout the brain and body). What that looks like for many of us is an improved ability to focus and an increased capacity to learn new skills. Super cool, right?!
And, the benefits don’t stop with the brain, but extend to our bodies as well! When we tap into our fat stores for energy, we are obviously diminishing the fat we carry. Studies have also shown that IF preserves muscle, unlike other calorie-restricting diets that can deplete muscle along with fat. Additionally, because the liver is not constantly releasing certain hormones that can cause inflammation, we see a decrease in inflammation in the body. Along with these benefits, IF also decreases insulin resistance, which leads to a decrease in obesity, diabetes, hypertension, cardiovascular disease and even some mental illnesses! Now, before you jump on board, let’s look at some basic guidelines for fasting. First of all, THIS DOES NOT WORK FOR EVERYONE! You need to listen to and trust your body! If it doesn’t feel right, don’t do it!
If you want to try it, however, you will need to figure out a fasting window of time that works for you consistently. Consistency is important. Here are some basic guidelines to keep in mind when you are ready to get started:
- 12 hours is the minimum amount of time needed to get into a fasting state, but 12 hours does not always get you there. It is also dependent on how much you have eaten, what you have eaten and what you do during the fasting period - remember, you need to use up all of the glucose and stored glycogen before you make the metabolic switch to using the energy stored in your fat cells.
- 14 hours done consistently over months is the timeframe that has been studied the most so has the strongest data to support it’s efficacy.
- Whatever your window, stop eating 2-3 hours before bed and wait at least one hour after you get up to eat.
- Drink lots of water, especially in the morning.
Another big (and somewhat controversial) question is, “What can I consume during my fasting window that won’t break my fast”? While there are differing opinions on this, I take a pretty conservative stance with my own fasting. If I am going to do it, I want to make sure I am doing it correctly. Therefore, I avoid anything that spikes my glucose level. This includes anything that is flavored (even if I don’t swallow it, like gum) and anything with calories. Here are some Meal Planning Tips to help you.
I have read that MCT’s (medium chain triglycerides - fats that are small enough to get through the blood-brain barrier) and pure fats may not break a fast for some people. However, I don’t eat any fats during my fast because I don’t want to put any fat in my body that my body can use before it taps into my own fat stores. Also, there is conflicting information on artificial sweeteners. I stay away from them in general and definitely avoid them during my fast.
However, Stevia seems to have minimal impact on insulin levels if you absolutely need something sweet. While I am fasting, I stick with lightly salted water (the salt helps to clear the glucose out of my system), unflavored black coffee and unsweetend tea.
Lastly, you might be wondering what you should eat when you are ready to break your fast. While there are many studies that show people lose weight simply by practicing IF without changing their diets, if we want to be as healthy as possible (and not undo the benefits of the fast), we need to focus on fueling our bodies with a variety of nutrient-dense foods. We want to consume healthy fats, proteins, and complex carbohydrates. We want to focus on eating more whole foods, fewer processed food, and less sugar.
With that in mind, I am going to make myself a frittata with olive oil, eggs, spinach, tomatoes and avocado right now! It’s time to break my fast!