Intermittent fasting has surged in popularity the past 5-10 years as one of the newest ‘diet trends’. Although the biggest mistake we see around fasting is that people perceive it as a diet instead of a lifestyle. The benefits of fasting are vast, but it is by no means an entry level diet approach - the body must be healthy and your nutritional foundation must be solid to get the benefits that fasting has to offer.
So if you’ve been considering fasting to drop a few pounds, or maybe you’ve tried fasting without much success - we recommend you read further and understand how to get the most out of fasting, and also whether it may do more harm than good for you!
Different Types of Fasting
There are two main ‘types’ of fasting that we see most commonly:
1) Time Restricted Eating -
What most people are doing nowadays as their form of intermittent fasting is actually what we refer to as ‘Time Restricted Eating’. This is where you shrink your eating window during the day. This will range anywhere from a 12 hour fast up to a 20 hour fast - leaving whatever time is left in the day as your ‘eating window’. This may include skipping breakfast or dinner, but there are technically no restrictions around what you consume during that window of eating.
If you’ve never tried fasting before, it's recommended to start with a smaller fasting window, around 12 hours, and build up to a larger fasting window.
The most common splits of fasting are:
- 12 hour fast/12 hour eating window
- 16 hour fast/8 hour eating window
- 18 hour fast/6 hour eating window
- 20 hour fast/4 hour eating window
Most programs will say that water, coffee (plain black), and non-caloric drinks are fine to consume during your fast. During the eating window, there are no ‘standard’ recommendations, which is where this diet trend tends to go wrong. You must still abide by the rules of nutrition to have progress and adequate nourishment. Shortening your eating window makes it hard to eat enough, so ensuring that you have proper calorie intake and also high quality foods is a must.
2) Full Day Fasts -
This is exactly what it sounds like - a full fast for 24 hours, which is usually performed 1-2x per month or once per week. This is not something we recommend to many individuals, only those that have a very solid base of longer fasts and have been successful with them and how they feel when doing them.
The goal with these is to break your fast with a normal sized meal, not a feast to try to make up for the fast, and also to try to keep exercise more non-stressful on this day. It should also be noted that the benefits of full-day fasts are not only different, but more impactful than time-restricted eating, which we will get into more later.
The Foundation to Fasting
With any fasting approach, it is important to understand that fasting alone is not some magic pill. Simply closing your eating window will not vastly improve your health or cause immediate weight loss unless you were severely over-eating prior, and by closing the eating window, we have reduced calories naturally.
For individuals to get the highest benefit from fasting, there must first be a solid foundation of nutrition and lifestyle in place. We see this with our clients all the time, when people have blood sugar imbalances due to inconsistent eating schedules or high levels of stress, cortisol dysregulation is the culprit. If we aren’t managing adequate calories and nourishment, and we don’t keep stress under control, intermittent fasting makes blood sugar worse.
So before you even attempt intermittent fasting to gain the benefits, a great checklist run through would be the following:
- You are eating adequate calorie intake in the form of high quality foods and proper balance of foods between proteins, carbohydrates, and fats. (i.e. you aren’t eating 1400 calories or less of processed food)
- You are eating regularly throughout the day (i.e. every 2-4 hours).
- You are sleeping through the night most nights and wake up feeling rested.
- Your weekdays and weekends look similar in terms of intake.
- You are not in a high stress time in your life.
- You don’t have any known blood sugar regulation issues (i.e. hyperglycemia, reactive hyperglycemia, or hypoglycemia).
These habits are much more impactful than many realize, and simply putting these in place might bring greater progress than you’d think. They are especially necessary to ensure your body responds in as positive of a way as possible if you do choose to implement a fasting window.
Benefits of Fasting
There are quite a few benefits to fasting, but like we just discussed, these benefits are not going to be present without a healthy foundation in place first!
- You Begin to Burn Fat vs. Sugar -
Our body utilizes the calories we consume as our energy source. The main energy source the body wants to utilize and will utilize are carbohydrates. If our cells don’t use all of this available glucose, once broken down from carbohydrates, we store it as fat. Although during a fast, our cells switch from burning glucose to burning fat (aka triglycerides). This shift has been seen to occur as early as 10 hours into a fast, but the most pronounced effect seems to happen between 16-18 hour fasts (SOURCE).
This obviously depends on the types of food you tend to consume and what type of diet you follow, but fasts do tend to bring our body into a fat burning state versus the normal sugar-burning state we are often in.
- Improves Insulin Sensitivity -
When we consume food, particularly carbohydrates, our blood sugar increases and in turn, insulin floods our system to facilitate where that glucose floating around in the blood goes. When we constantly consume food, insulin never gets a break, and in worst case scenarios you can develop insulin resistance or Type 2 Diabetes. On the contrary, when you fast, insulin levels drop - allowing the body to develop sensitivity with insulin again (SOURCE).
This can help to aid weight loss, and has even been shown to help prevent and reverse diabetes (SOURCE).
- Increases Human Growth Hormone (HGH) -
Fasting has shown to skyrocket human growth hormone levels by up to 5x their normal amount - which is significant because as we age, HGH tends to naturally decrease (SOURCE). We’ve talked many times before about how important maintaining muscle mass as we age is, and fasting can help to not only maintain muscle with higher levels of HGH, but also decrease fat tissue!
- Increases Your Cellular Health -
Fasting is a form of stress to the body that we consider a ‘good stress’. Other variations are things like high intensity exercise, cold therapy, infrared saunas, and oxygen deprivation - but essentially, what each of these does, including fasting, is create a ‘what doesn't kill you makes you stronger’ situation.
This is because when our cells undergo this stress response, it initiates cellular autophagy and turnover. During cellular autophagy - where the cell basically takes out its own trash and regenerates itself - it allows for old unhealthy cells to become new cells. This protects our body from disease, increased aging, and even oxidative stress and inflammation (SOURCE).
This effect has been shown to be much more prominent in full day fasting vs. intermittent fasting.
- Improves Circadian Rhythm -
We’ve done a whole blog on circadian rhythm and it’s importance to our health, but circadian rhythm is basically our body’s internal clock. It helps us to maintain energy during the day, it helps us to get adequate and restful sleep at night, and it helps regulate hunger. Research has also shown that our metabolism seems to be most efficient when we adhere to eating when it is light out, and fasting while it is dark. Unfortunately, in today’s world, many individuals eat late at night, or even overnight, which can impair our metabolic abilities.
By fasting, you are restoring your body’s natural internal clock and allowing for higher metabolic efficiency to break down and process your food versus storing it.
Who Should Avoid Fasting
There are obviously numerous benefits to fasting and time-restricted eating, but like every nutritional approach, there are certain populations where this type of eating can do more harm than good. Some populations to be wary of the fasting approach:
Chronic Under-eaters - If you are already someone that struggles to consume enough food, or tends to under-consume, shrinking your eating window is not going to be something we recommend as it will only make it harder to get your body proper nourishment.
Trying to Conceive - If you are working to maximize fertility, the stress that fasting can create on female hormones is not recommended for this population.
High Stress or Chronic Fatigue- If you battle chronic fatigue, or have known HPA Axis dysregulation, fasting will tend to drive further stress on the body in a negative way.
Pregnant or Breastfeeding - It is important to provide the body adequate calories and regulate blood sugar during this time, it is not recommended to fast.
- Other populations: Underweight individuals, thyroid conditions, not getting adequate sleep, chronic infections.
Like with any nutritional approach, it depends on the individual and the situation as to whether time restricted eating or fasting would be beneficial for you. There are obvious benefits to fasting that may seem enticing, but we always recommend addressing the foundational aspects of nutrition and lifestyle before diving into a more advanced approach to eating like fasting provides.