Intermittent fasting (IF) is a dietary pattern that involves cycles of fasting and eating. What IF doesn’t do is specify which foods you should eat, but rather when you should eat. In general, people practice IF by restricting their food intake to certain hours of the day or days of the week. The main goal is to ease your body into the practice rather than trying to drastically change your habits with an all-or-nothing approach.
In today's world, we find ourselves almost constantly surrounded by food. Knowing when and what to eat is a never-ending struggle, filled with tough decisions and efforts to balance long-term and short-term goals. This is why diets like intermittent fasting have become more popular over the past few years. A growing body of evidence suggests that intermittent fasting (IF) has a large number of health benefits, including weight loss, improved insulin response, and lower blood pressure. One of the best things about intermittent fasting is that you get to decide how long you want to fast, and what type(s) best fit your lifestyle and goals.
Intermittent fasting is a powerful tool that offers a less-restrictive way to improve your daily health and increase energy levels. It’s important to remember that there is no one-size-fits-all approach, the key is to find a method that works for your body and lifestyle. If you’re new to IF, start with shorter cycles and increase the length of your fasts gradually. Always be sure to listen to your body — if you start to feel off, adjust accordingly.
Intermittent fasting can transform an individual's relationship with food by encouraging a more mindful and intentional approach to eating. By imposing specific windows of eating and fasting, it fosters a deeper awareness of hunger cues and signals from the body. This heightened awareness allows individuals to differentiate between true hunger and emotional or habitual eating, helping them make more conscious food choices.
Furthermore, intermittent fasting can break the cycle of constant snacking and late-night eating, promoting structured meal planning and healthier eating patterns. It encourages individuals to savor their meals, focus on nutrient-dense foods, and appreciate the importance of balanced nutrition. Fasting can help you reset your relationship with food. By fasting for periods of time, you can train your body to feel satisfied on less food. This can lead to eating less overall and consequently, weight loss. When you fast, you’re likely to eat less overall. You may find that you’re less inclined to overeat or make impulsive food choices as often.
When you’re used to eating regularly throughout the day, it can be easy to mindlessly snack or overindulge. Frequent eating keeps blood sugar levels high and signals that there is no need to burn any fat. There’s a constant supply of food coming in, so your body just keeps on storing more away.
When you fast, you’re forced to use up the glucose stored in the cells - allowing your body to burn fat for fuel instead. For this reason, fasting can actually increase your metabolic rate. It works as a powerful weight-loss tool on both sides of the calorie equation. Helping to boost your metabolism (increases calories out), while also reducing the amount of food you eat (reduces calories in).
Intermittent fasting promotes the body's utilization of stored fat for energy during fasting periods, further supporting weight loss. During periods of fasting, especially in extended fasts, the body depletes its glycogen stores, which are the primary source of energy derived from carbohydrates.
Once glycogen is depleted, the body shifts into a state called ketosis, where it begins to rely on stored fat as its primary fuel source. This process involves the breakdown of triglycerides into fatty acids and the conversion of these fatty acids into molecules called ketones. Ketones can cross the blood-brain barrier and provide the brain with an efficient energy source during fasting. As a result, fasting can lead to increased fat oxidation and promote weight loss, making it a valuable tool for those looking to reduce body fat and improve their metabolic health.
Your Body Can Take It
Evolution + Fasting
Ancient hunter-gatherers evolved to survive and make it through occasional periods of scarcity to remain functional for extended periods without food.
If you’re considering trying intermittent fasting, it’s important to understand what's happening in your body hours after your last meal.
During the first four hours after eating, the body is in what’s known as the "anabolic growth phase" - meaning that nutrients are available and the body can use them to build muscle, burn fat, or store them. Your body is using up the energy from your last meal to fuel your daily activities, as well as for cellular and tissue growth. Right after a meal, your blood sugar levels rise, causing your pancreas to release the hormone insulin to regulate levels. Insulin signals the body to burn energy by pushing glucose (sugar) into cells. Excess sugar is stored for later use in the liver as glycogen or stored in fat cells.
After a meal, you digest and absorb food into your bloodstream. Then, your pancreas releases insulin to manage the rising glucose levels. Insulin helps store excess glucose as glycogen in your liver. Once your liver’s glycogen storehouse is full, the remaining sugar is turned into fat.
As this phase begins, your blood sugar and insulin levels will start to decline. You'll also experience a drop in your leptin levels - the hormone responsible for telling you you're full. Ghrelin, the hormone that signals hunger, will rise. In the early fasting state, your body switches from the anabolic to the "catabolic," or breakdown, phase, when all those stored nutrients can now be put to use. When insulin levels fall, your body will begin burning off your glycogen stores of glucose from your liver. That’s why it’s so important to wait that long between meals so you can keep recycling your glycogen stores. Otherwise glycogen can build up and contribute to fatty liver.
Eventually, your body will run low on stores and start searching for another energy source. A process called lipolysis (fat-burning) begins. This causes the breakdown of fat cells, which are converted into energy. A few hours post-meal, about 60% of your energy will come from the liver’s glycogen storehouse and the other 40% comes from fat burning. At night, this reverses, with 60% of your energy coming from stored fat. Typically, it takes between 4 and 18 hours of fasting for you to burn through glycogen stores. Your body will start to break down its fat stores even before it finishes using up all the glucose in your system. With this in mind, research suggests that intermittent fasting can help boost your fat-burning abilities!
A few hours after a meal, insulin levels begin to drop. This signals the body to release energy from glycogen storage sites in the liver and muscle. Fat burning begins.
When glycogen stores are finally depleted, your body will transition into a state called ketosis, where fat becomes the primary source of energy. Ketones are the natural breakdown product of burning fats. As fat cells are broken down for energy, ketone bodies are created and released into the bloodstream, carrying a number of key benefits. When your gut has finished absorbing your last meal, your pancreas stops producing insulin.
As insulin levels remain low, the amount of glucagon – a hormone that controls blood sugar levels – signals your liver to slowly start releasing the stored sugar (glycogen) into your bloodstream. It’s during this stage that your body also starts to do something really interesting. It activates a natural healing process known as autophagy. Autophagy helps your cells clean up and get rid of any old or damaged components. The idea behind autophagy is that the body recycles its cell components to protect against stressors and regenerate healthy cells. To enter this phase, your body requires low liver glycogen. .
During the fasting state, fats take over as a primary energy source. Glucagon levels rise to prevent blood glucose levels from dropping too low, and Autophagy begins.
Learn why hydration is a cornerstone of maximizing your fasting experience including maintaining adequate electrolyte levels to maintain your energy + wellness during fasting periods:
Here are answers to the most common questions about intermittent fasting:
All in all, any amount of calories will break a fast. You should avoid calorie-containing drinks or foods during this time.
Yes. During fasting hours, you can drink water, black coffee, or tea - with no added sweetener, cream, or flavoring of course.
Add ¼ teaspoon of natural sea salt to 1L of your drinking water to get those vital minerals back in your body. Aim to consume at least half your body weight (in ounces) of mineral water. If you want to invest in your health, a liquid electrolyte supplement can be beneficial to optimize hydration
Yes, you can take supplements while intermittent fasting! Keep in mind that some supplements like fat-soluble vitamins may work better when taken with meals.
Yes. In fact, working out while fasting can help you burn more fat and improve your overall health. However, it's important to remember that you shouldn't overdo it. If you're new to intermittent fasting, start slowly by working out for 20-30 minutes a day. Once your body gets used to the fasted state, you can gradually increase your workout time.
If you're doing a high-intensity workout, it's best to do so during non-fasting periods, so you can eat something before or during your workout. This will help you avoid feeling lightheaded or dizzy.
Losing muscle while fasting is a common concern, especially among those who are new to fasting. However, there is no need to worry. Fasting does not cause muscle loss. In fact, research has shown that intermittent fasting may actually be more effective formaintaining muscle massduring weight loss than non-fasting diets. According to a 2011 study, intermittent fasting causesless muscle lossthan regular calorie restriction diets.
There's no evidence that intermittent fasting reduces your metabolic rate any more than other diets. The argument against intermittent fasting is that it puts your body into "starvation mode", which prevents you from burning fat and shuts down your metabolism. While it’s true that long-term weight loss can cause you to burn fewer calories over time, this happens no matter what method you use.
A short-term fast can actually increase your metabolic rate because norepinephrine levels increase, which stimulates your metabolism and signals your fat cells to break down body fat. Research shows that fasting for up to 48 hours can boost metabolism by 3.6–14%. However, with longer fasts of 3 or more days, your metabolism can reverse, decreasing instead.
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