Fasting has become an increasingly popular health and wellness trend in recent years. Proponents claim that periodically abstaining from food can provide a variety of benefits, from weight loss to reduced inflammation and improved cognitive function. But is fasting truly as miraculous as some make it out to be? In this post, we’ll explore the science behind fasting and uncover some of the biggest misconceptions about this ancient practice.
What Is Fasting?
At its core, fasting simply means abstaining from food and caloric beverages for a period of time. There are several different types of fasts:
- Intermittent fasting involves restricting eating to a specific window of time each day, such as 16 hours of fasting and 8 hours of eating. This is sometimes called time-restricted eating.
- Water fasting means consuming only water for a predetermined length of time, usually 1-3 days but sometimes longer.
- Juice fasting allows fruit or vegetable juices but no solid food.
- Dry fasting prohibits all food and liquids, even water. This extreme type of fast is not recommended.
- Alternate day fasting alternates normal eating days with fasting days where calories are restricted.
No matter the type, the goal of fasting is to put the body into a mild biological stress state, triggering beneficial changes on a cellular level.
Top 5 Fasting Myths
Now that we know what fasting entails, let’s examine some common myths about this practice.
Myth #1: Fasting Puts Your Body in “Starvation Mode”
One of the biggest concerns people have about fasting is that it will cause the body to enter so-called starvation mode. In starvation mode, the theory goes, your metabolism slows down to conserve energy, you stop burning fat and start burning muscle, and your body hangs on to every calorie you eat.
In reality, studies show that short-term fasting does not cause starvation mode. In one trial, men who fasted every other day for 22 days displayed no decrease in metabolism. Research has also shown that fasting triggers an increase in norepinephrine, a hormone that helps burn fat. Short fasting periods temporarily boost metabolism, not slow it down.
Myth #2: Fasting Will Make You Lose Muscle
Related to the starvation mode myth is the belief that abstaining from food leads to muscle wasting. However, scientists have found that fasting does not consume muscle to a greater extent than regular dieting.
In one study, participants practiced alternate day fasting for 3 weeks. On fast days they consumed 25% of their normal calorie intake. Despite the dramatic calorie reduction on fast days, participants lost only 0.1 kg of lean tissue and 2.2 kg of fat mass over 3 weeks.
As long as your fasts are time-restricted and you maintain physical activity, you’re unlikely to lose muscle mass. In fact, fasting triggers the release of growth hormone, which preserves lean tissue.
Myth #3: Fasting Kills Your Metabolism Long-Term
Studies do show that more extreme “Famine” conditions, with severe calorie deprivation for long periods, can suppress metabolism. However, the types of fasts people voluntarily practice today are much different. Evidence suggests that intermittent fasting and alternate day fasting do not impair your metabolism over the long haul.
For instance, in one trial participants maintained alternate day fasting for a year. At the end their resting metabolic rate was no lower than at the beginning. Research has also demonstrated that cheat days can counteract any transient metabolic slowdown from fasting. Enjoying higher calorie meals 1-2 times per week keeps your metabolism revved.
Myth #4: You Can’t Build Muscle While Fasting
No one would argue that fasting helps you maximize muscle growth. However, with targeted eating and exercise on non-fasting days, you can absolutely build muscle mass through intermittent or alternate day fasting.
In one 10-week study, participants fasted every other day but ate high protein on their normal calorie days. Despite the fasting periods, these subjects gained muscle mass and strength over the course of the trial. Remember: fasting preserves lean tissue. As long as you consume enough protein on eating days, you can still gain muscle.
Myth #5: Fasting Disrupts Your Workouts
Another common fasting myth is that abstaining from food will tank your workouts. Research suggests this isn’t necessarily the case. In a 2021 study, overweight police officers fasted for 19 hours and then did high intensity interval training (HIIT). The fasting group showed identical improvements in VO2 max and power output as the control group who ate normally before exercise.
How is this possible? During short fasts, you tap into fatty acids for fuel rather than glycogen from carbohydrates. Your body’s fat stores provide a nearly unlimited source of energy! Some people even experience increased strength and focus when training fasted. Just be sure to stay hydrated and consume electrolytes.
Should You Try Fasting?
Now that we’ve busted some myths, let’s explore who may benefit from a fasting regimen. Fasting is not for everyone, so consider these factors if you’re thinking about giving it a try:
- Consult your doctor – Anyone on medication or with a medical condition should speak with their physician before fasting.
- Start gradually – Begin with 12-14 hours overnight, slowly extending your fasts over time. This allows your body to adapt.
- Time matters – Women may react differently at different points in their menstrual cycle. Track your cycle and fast accordingly.
- Listen to your body – Hunger, fatigue, shakes, etc are signs to break your fast. Fasting should not feel torturous.
- Stay busy – Boredom can trigger cravings and the desire to eat. Schedule activities and distractions during fasting hours.
- Stay hydrated – Sip water, herbal tea, or black coffee to support energy and hunger levels during fasts.
- Mind electrolytes – During longer fasts, supplement with electrolytes like sodium, potassium and magnesium.
- Break fasts gently – Start with broth, fermented foods, non-starchy veggies. Avoid heavy greasy meals.
- Exercise strategically – Moderate activity enhances fasts. Rigorous workouts may necessitate fuel. Play it by ear.
- Plan eating periods – To avoid cravings and overeating, plan healthy balanced meals for non-fasting times.
The Truth About Fasting
When performed strategically, fasting may confer benefits like blood sugar stabilization, reduced inflammation and improved cardiovascular health for some people. However, fasting is often overly hyped as a cure-all solution. The truth is that abstaining from food periodically can be healthy but is no “miracle.”
Any positive effects of fasting depend heavily on your lifestyle when you are not fasting. If you binge on junk food when not abstaining, you may not see results. Prolonged fasts can also be risky without medical guidance. Intermittent and alternate day fasting may provide health advantages, but extended water fasting can be dangerous.
The preponderance of evidence suggests that fasting carries minimal risks for most people when done properly. But as with any health fad, it’s important not to get swept away in the hype. Be skeptical of any approach that promises extreme or miraculous benefits. Evaluate fasting based on established science, not celebrity endorsements or anecdotal success stories that are not typical.
At the end of the day, fasting is one tool for wellness, not a panacea. Pay close attention to your body, consult doctors, and approach purported benefits with a healthy dose of skepticism. Any diet plan should be safe, sustainable and tailored to your individual needs.
Human beings are complex and there are no cure-alls in health. But used strategically, fasting may provide advantages for some people. With realistic expectations, a smart lifestyle approach and the right precautions, periodically abstaining from food can be part of an overall healthy regimen for many individuals.
