Approximately three years ago I seriously began to consider the application of Intermittent Fasting. When I would bring the idea of it up with clients, I would see their eyes start to widen with a tilt of their heads wondering to themselves how could I be crazy enough even to consider trying this idea.
Fast forward to the present. Now, I've got clients asking with more frequency "How do you Intermittent Fast? Are 16 hours better than 14, or 12? Should I do a 24 hour fast? Etc. With an increasing amount of questions about Intermittent Fasting coming my way. It seems, at least on this topic, that I'm not so crazy after all!
What is Intermittent Fasting?
Intermittent fasting is the practice of cycling between periods of eating and intentional fasting, or abstaining from food. Humans have fasted since we appeared on the biological and evolutionary scene, whether for religious or cultural purposes or out of necessity during times of scarcity.
In the world we're living in today, it’s rare for most modern people to skip a meal when there is food literally on every corner. Research is beginning to compound on how fasting intermittently affects weight loss and body composition. Unlike traditional “diets” that dictate what you eat, intermittent fasting focuses on when you eat and can be a powerful practice for better health.
Benefits of Intermittent Fasting
The benefits of fasting are similar to those of calorie restriction, which has been shown to have positive effects on weight loss and potentially even longevity. The issue I've noticed for most people is that counting calories is exceptionally tedious, requires a lot of guesswork, and frankly is an advanced technique that needs practice. Long-term calorie restriction without regular re-feeds can be catastrophic for your hormones and lead to lower energy levels, loss of muscle or leave you feeling hungry and cold. Not fun.
That’s where intermittent fasting comes into play.
Intermittent fasting has been shown to mimic the benefits of calorie restriction without the potential drawbacks and the need to restrict food intake intentionally. Studies suggest that intermittent fasting is as effective as traditional calorie-restricted diets for weight loss due to specific benefits that occur during the fasting window:
Improved Fat Burning: Human studies have shown that fasting for periods of 12 or more hours can enhance fat burning and induce mild ketosis.
Increased Metabolic Rate: Short-term fasting has been shown to lead to increased energy expenditure and metabolic rate in human studies.
Blood Sugar Regulation: Fasting can improve insulin sensitivity, lower overall levels of blood sugar, and reduce systemic inflammation, all of which are crucial factors for appetite regulation and metabolic health.
Normalized Appetite: Fasting has been shown to help regulate ghrelin, the “hunger hormone.” Ghrelin antagonizes leptin, the hormone responsible for telling us we’re satiated, so balancing the two is key to regulating appetite.
Better Muscle Retention: Intermittent fasting stimulates the production of growth hormone and testosterone, especially in overweight populations. These hormones help you maintain muscle mass while losing weight, and the more muscle you have, the more calories you burn at rest.
In addition to its benefits for fat loss, intermittent fasting has a host of other health optimizing benefits:
Autophagy: A repair process wherein cells dispose of damaged proteins and replace them with new ones. This process has been linked with anti-aging, longevity, and improved metabolic health because it keeps cells young and functioning optimally.
Improved Gut Health: Fasting can make your gut stronger by giving it a break from digestion, protecting it from the negative impacts of stress, increasing levels of good bacteria, and killing off harmful microbes.
Improved Blood Lipid Profiles: Fasting has been shown to improve many blood lipid markers including blood pressure, cholesterol, blood sugar, and triglycerides.
Better Energy Levels: Most people equate hunger with lethargy, but fasting tends to lead to increased energy levels and cognitive function. This is due to increased fat metabolism and ketone production.
Intermittent fasting is a simple way to regulate energy intake without the need to weigh, measure, track, and count every morsel of food you consume. Many people find fasting to be a more comfortable alternative to calorie-restriction for losing fat, increasing energy levels, and improving metabolic health.
Different Styles of Intermittent Fasting
There are several different styles of intermittent fasting, each of which consists of varying fasting and feeding windows to support different goals. Here are some of the most common types of intermittent fasting:
Time-Restricted Eating: This is an excellent approach for beginners. Time-Restricted Eating involves not eating between dinner and breakfast the next day. If you’ve ever gone to bed a few hours after dinner, gotten a full night’s sleep, and waited a few hours to eat breakfast, you’ve already done this style of fast!
Fasting Duration: 10-14 hours
What This Looks Like: If dinner ends at 8 PM, bedtime is at 10 PM, wake up at 6 AM, breakfast would happen between 8 and 10 AM. Only water is consumed during the fasting window – no other beverages and no supplements.
16:8 Fasting: Also known as the LeanGains Method, Which was brought into prominence by Martin Berkham involves fasting for 16 hours each day – as simple as skipping breakfast. This method is popular because a full day’s worth of food could be fit into the feeding window, making it easy to sustain long-term.
Fasting Duration: 16 hours
What This Looks Like: If dinner ends at 8 PM, eating resumes at 12 PM the next day. Feeding could be compressed into a shorter window of 6 hours after fasting for 18.
Eat-STOP-Eat: Perhaps the most straightforward fasting protocol, the Eat-STOP-Eat method involves fasting for 24 hours once or twice a week. It’s highly effective for people who have a lot of weight to lose.
Fasting Duration: 24 hours
What This Looks Like: If dinner ends at 7 PM, eating will not resume until 7 PM the next day. Frequency: 1-2x per week
Intermittent Fasting Guidelines
So, which type of intermittent fasting is best for you? The truth is that you would need to give one a try to discover how your body will respond. Choosing a method that is sustainable for your lifestyle is a great starting point.
Here are some guidelines that apply to all types of intermittent fasting.
How Long to Fast: The ideal length of fast depends on what your body can tolerate. Start with a short fast of 12 hours and work up from there by adding just an hour at a time.
How Often to Fast: Some people fast for 12-18 hours each day, others prefer less frequent fasts of up to 24 hours. The key is to choose a protocol that’s sustainable and fits effortlessly into your schedule.
What to Eat Before Fasting: Before you fast, have a reasonably sized meal with protein for satiety, fiber to slow digestion, and fat to provide you with slow-burning energy. There are plenty of recipes HERE
What to Eat to Break a Fast: You can break a short fast (12-16 hours) with a normal-sized meal comprised of healthy, whole foods. For longer fasts, consider starting with some bone broth and digestifs like lemon and apple cider vinegar to ease the body back into eating.
What to Consume While Fasting: Most experts agree that you should consume water and avoid significant sources of calories during fasting. However, even the top fasting experts can’t come to a consensus on what exactly breaks a fast.
Let's take a look at what they are saying.
-Dr. Satchin Panda believes that anything aside from water will break a fast.
-Dr. Jason Fung believes that zero-calorie beverages like coffee and tea will not break a fast. -Dr. Valter Longo’s Fasting-Mimicking Diet involves consuming small amounts of food while still reaping the benefits of fasting.
All of that information can feel confusing, but that's the joy of being at the frontier of a field. You get to try all types of protocols to see what works.
Here’s a simple solution for those that are not trying to sort through all the cutting edge science: instead of worrying about what “breaks” a fast, consider how what you consume can enhance or inhibit the benefits of your fast.
Here are a few suggestions to make intermittent fasting easier and accelerate weight loss:
Black Coffee and Tea: Caffeine can help suppress hunger and increase fat oxidation. The polyphenols in these beverages might even enhance autophagy during fasting.
Electrolytes: If you only drink water during your fasting window then you flush out electrolytes, which are vital for essential physiological functions. You can maintain electrolyte balance by merely adding 1 to 2 teaspoons of Celtic sea salt or supplemental electrolytes to your first glass of water each day.
Essential Amino Acids (EAAs): Though EAAs have been shown to inhibit autophagy, they can make fasting easier and more sustainable by suppressing hunger and cravings, improving energy levels, maintaining muscle mass, and supporting training in a fasted state. In other words, if your primary goal for fasting is to lose weight and improve body composition, EAAs will not negatively impact your fast and will likely improve your results. Look for an EAA formula that has minimal calories and is free of added fillers or sugars, as those components will take you out of a fasted state.
Pay attention to your body as you experiment with intermittent fasting. If you’re losing fat, feeling good, and performing well during your fasting window, then keep it going! If you find yourself feeling sluggish and see your weight stalling, then modify as necessary. Fasting has many health benefits, but it doesn’t always work for everyone.
Training While Intermittent Fasting
You might be wondering: can you train while you fast? The answer is yes, and fasted training might even accelerate your fat loss efforts.
Here are some tips to maximize workouts during fasting:
Do the Right Training. If you exercise in a fasted state, opt for workouts that are easily fueled by body fat. Passive aerobic exercise like hiking or high-weight low-rep strength training are great options. It’s best to avoid intense anaerobic, glycolytically-demanding exercise like martial arts and CrossFit as glycogen is depleted while fasting. This is especially true for women.
Take Time to Adapt. If you’re brand new to fasting, you might see a slight decrease in performance. You will adapt over time as your body gets used to tapping into stored body fat for energy.
Train at the Right Time. Women typically see more fat loss when they eat pre-workout and fast after exercise. Men, on the other hand, are more flexible but tend to see benefits when training fasted and having a post-workout meal.
Supplement With EAAs. EAAs increase fat oxidation during workouts and keep the body from cannibalizing muscle when taken before fasted training. Taking EAAs is also a potent hack for extending a fast post-workout, as they provide muscles with the proteins needed for rebuilding and recovery but allow you to continue burning fat until the next meal.
Intermittent Fasting for Women
Due to different hormonal profiles, women have to take some special considerations when intermittent fasting. For women, fasting creates a significant reduction of Kisspeptin, which is a precursor to reproductive hormones. Therefore, fasting can lead to a substantial decrease in sex hormone production in women, which can cause a host of symptoms including hormonal imbalances, loss of menstrual cycle, infertility, or thyroid issues. Women also produce less leptin than men, which means that they are more sensitive to hunger when food intake is restricted.
Should women try intermittent fasting at all?
Yes, but there are a few women that the answer "it depends" is relevant. Fasting is not a good idea for women who are very lean (under 18% body fat) and/or extremely active, have subclinical hypothyroidism, have hormone disorders, have a history of an eating disorder, or are pregnant, breastfeeding, or trying to conceive.
Healthy women typically do best with shorter or less frequent fasts, such as:
The Crescendo Method, which involves fasting for 12-16, hours 2-3 days a week on non-consecutive days. Ideally, fasting would fall on rest days as opposed to training days.
Eat-STOP-Eat, 24-hour fasts once every 1-2 weeks.
Occasional Prolonged Fasting, like a Fasting-Mimicking Diet or an Elemental Diet for 3-5 days, done 1-4 times per year.
Here are some other tips on how women can take advantage of the strong benefits of fasting without sabotaging their hormones:
Avoid intense protocols like CrossFit and long-distance running during fasting. Opt instead for low-rep strength training, low-intensity cardio like hiking or swimming, and therapeutic movement like restorative yoga.
Sleep, ensure you're doing everything possible to get plenty of quality nighttime rest.
Minimize stress, and prioritize relaxing activities.
Eat adequate calories from nourishing foods during feeding windows, including plenty of healthy fats to optimize hormone production.
Common Concerns of Fasting
Will intermittent fasting make me lose muscle? Remember that intermittent fasting is more muscle-sparing than traditional dieting. You’ll only lose muscle if you don’t consume adequate calories (especially protein) during your feeding window. Strength training and supplementing with EAAs will also help support muscle maintenance during fasting.
Will intermittent fasting slow down my metabolism? Fasting has not been shown to reduce metabolism. Your metabolism won’t slow down as long as you exercise and eat enough calories during your feeding window.
When do I take supplements during intermittent fasting? Most supplements contain insignificant amounts of calories and can be consumed during the fasti