Fasting has been a widespread practice throughout most of human history. It all began involuntarily with the “feast or famine” realities of hunter-gatherer times and continued voluntarily as several religious groups have used fasting in yearly traditions and daily routines for millennia.

Most recently, we voluntarily use fasting for its recognized benefits for our health and well-being.

Up until the technological revolution and the surge of the food industry, food production and consumption were related to direct effort and preparation. We primarily ate fresh or preserved/fermented foods—a stark contrast to today.

Think about how the technology of refrigeration alone changed how we consume meat and produce!

Today, typical American eating habits look much different, earning the well-deserved “SAD Diet,” or Standard American Diet. Our dietary staples are processed, concentrated energy sources with low nutritional value, while simple, nutrient-dense whole foods are few and far between.

Benjamin Franklin claimed, "The best of all medicines are resting and fasting." In this blog, we explore how the ancient and time-tested practice of fasting can benefit our cardiometabolic health, energy levels, and long-term wellness.

What is Fasting?

Fasting has many definitions, applications, and variations. For the purpose of this article, we will simply define fasting as “a period of non-eating that begins when you stop consuming calories.”

Both what and when we eat determine how our bodies create energy from food and utilize energy stored in body fat, proteins, and other internal sources. In practice, as long as we are eating and snacking, our body prioritizes processing the energy it gets from food, especially carbohydrates.

If we eat more calories than we can immediately use for energy, they are generally stored as body fat. Hormonal signals also play a key role in fat storage.

What Happens When We Fast?

When you fast (stop consuming calories) for long enough, you use up your immediately available calories from meals and snacks. Then, your body switches to seeking internal energy sources. We call this “metabolic switching.”

What source does the body turn to for fuel? Most commonly and applicable to this discussion, it switches to stored fat. Now you might see why fasting has become a hot topic in the world of weight management.

How long do you need to fast for this metabolic switching to take place? Typically, about 2-4 hours, but it depends on several factors:

• The amount of calories consumed in the most recent meal
• The type of calories consumed in the most recent meal
• Your metabolic rate, which is affected by hormonal signals, exercise and movement demands, etc.
• The efficiency of your mechanical digestion (chewing food enough, strength of digestive enzymes, etc.)

As you can see, our bodies are evolutionarily designed to adapt to alternating periods of scarcity and sufficiency. Fasting is a way we “practice” strengthening the efficiency of our metabolic switching pathways.

Common Types of Fasting and Where to Begin

Intermittent fasting (IF) is a particular method of fasting that’s drawn attention in research and wellness spheres alike. It’s an umbrella term that applies to describe both Time Restricted Eating (TRE) and Alternate Day Fasting (ADF).

There are many other forms of fasting, such as Fasting Mimicking Diets (FMD), that have overlapping benefits to intermittent fasting. For this section, we’ll explore TRE further.

Time-Restricted Eating is often the most accessible approach for beginners. As the name suggests, fasting periods are introduced at specific time intervals. The most common is a 12/12 fast – 12 hours of non-eating and 12 hours in which you consume your daily calories (i.e. fast from ending dinner at 7:00 pm to starting breakfast at 7:00 am).

Other common TRE intervals are 16/8 and 20/4, with 16 and 20 hours being the fasting windows. When you reach a 24-hour fasting period, it becomes Alternate Day Fasting. Prolonged fasting may not be for everyone, but research shows some people can undergo days or weeks of fasting. Proper medical guidance is definitely recommended to make sure your unique health situation is considered before prolonged fasting.

Potential Benefits of Modern Fasting

Constantly living in a state of calorie and carbohydrate excess means your body virtually never switches from burning what you eat and drink to burning stored fat – a common reason for weight loss difficulties.

To heighten the issue, as with any consistent environment, your body can hormonally adapt to this situation, making the capacity for fat-burning even less efficient.

Fasting trains your body to efficiently use carbohydrates and turn to stored fat as an energy source. Of course, it can be helpful for weight management, but that isn’t the only reason to consider this practice.

Other potential research-backed benefits of fasting include:

• Resetting the bowels and digestive process
• Supporting blood sugar regulation over time (consult your healthcare practitioner if you have blood sugar concerns such as pre-diabetes or diabetes)
• Optimizing energy-producing pathways in the body
• Supporting emotional regulation and mood
• Improving blood pressure regulation

Tips for Success with Fasting

First, if you’re considering fasting, it’s important to consult with a healthcare practitioner who can tailor advice to your unique situation and needs. Fasting can be safe and effective when practiced appropriately.

For example, improper fasting techniques, including extreme fasting or calorie deprivation, or fasting with certain health conditions can put the body into “starvation mode.” This can complicate weight loss efforts, and negatively affect hormone function.

Here are some tips to help you experience the benefits of fasting and avoid common pitfalls and potential complications:

• Prioritize eating whole food sources with quality proteins and healthy fats to sustain energy while fasting. Fasting does not replace healthy eating.
• Drink plenty of water with a quality, low-sugar electrolyte supplement to maintain hydration and electrolyte status.
• Eat your first meal or a nutrient-rich snack before exercising.
• Prioritize light to moderate intensity movement, and refrain from pushing your body past its limits.
• Consider including the support of a quality multivitamin supplement to maximize nutritional intake.
• Make sure you’re consuming enough calories when you do eat. Fasting is different than calorie restriction. When combined, it’s particularly important to seek professional guidance and watch for nutrient deficiencies.
• Social support or fasting with a partner, friends, or family can make the process much easier. I always say, “Health is contagious!”
• Make fasting a ritual of intention and focus. There’s a reason fasting is integrated into major world religions – it can possibly enhance mindfulness, intention work, and self-awareness.
• Consult a healthcare practitioner or nutritionist with experience in fasting if you have unique concerns or chronic conditions such as diabetes, hypothyroidism, PCOS, or blood sugar issues.

Lastly, there really is no “one-size-fits-all” method for fasting. We are all biochemically unique individuals, and our metabolisms are no exception! Every health endeavor requires learning the general principles and finding the specifics that work best for you.

Keep in mind that your body is constantly changing – what works in this season of your life might have a different effect in a few years. Listen to your body, safely discuss with a knowledgeable health and wellness practitioner, and tailor a fasting plan specific to your needs and health situation.