Let's Start with a Failure Story
Coach Kai personally tried and failed at 16:8 intermittent fasting. The reasons for his failure are traceable and are often overlooked blind spots for most people.
Many people ask Coach Kai, "Have you ever tried fasting yourself?" The answer is yes, and he failed.
During his attempt at 16:8 intermittent fasting, Coach Kai set his eating window from 2 PM to 10 PM. As he habitually woke up early, there was nearly half a day between waking up and 2 PM when he couldn't eat. The result: mental fogginess, irritability, and uncontrollable eating once the eating window opened.
What was even more challenging was that his goal at the time was muscle gain, which required a considerably high calorie and protein intake daily. To consume the total calories needed for muscle gain within eight hours, he almost exclusively relied on high-calorie foods, eating until he was uncomfortably full every time. Ultimately, he gave up.
This experience is not meant to scare you, but rather to show that Coach Kai, upon analyzing it retrospectively, clearly identified the root causes of his failure—and these reasons are precisely the blind spots many people completely overlook when doing intermittent fasting.
What is Fasting? First, Understand the Types
Intermittent fasting comes in three main types: 16:8, 5:2, and alternate-day fasting. The core principle of all is restricting the eating window.
The core concept of intermittent fasting is simple: it's not about not eating at all, but rather eating within a specific time window and remaining fasted during the rest of the time.
Currently, there are three main types of fasting popular on the market:
- 16:8 Intermittent Fasting: Within a 24-hour day, fast for 16 hours and eat for 8 hours. For example, eat your first meal at 10 AM and finish your last meal by 6 PM.
- 5:2 Intermittent Fasting: In a week of seven days, eat normally for five days and follow a very low-calorie diet for two days. These two days are typically not consecutive, for example, Monday and Thursday. Specific calorie intake recommendations should be evaluated by a nutritionist based on individual circumstances.
- Alternate-Day Fasting: Eat normally on one day and follow a very low-calorie diet on the next, alternating between the two.
Each of these three methods has its own difficulties and applicable situations, but one thing is common: their essence is the same.
Debunking Myths: The Real Reason Intermittent Fasting Aids Fat Loss is Not "Fasting" Itself
The only reason intermittent fasting helps with fat loss is calorie deficit; fasting itself has no special fat-burning magic.
Many people, upon hearing that fasting can help with weight loss, feel that this method is magical, as if simply shortening the eating time will automatically burn fat. This perception needs to be directly corrected.
The fundamental reason why intermittent fasting can aid fat loss is only one: calorie deficit. A shortened eating window means that the total calorie intake is relatively easier to reduce, naturally making it easier to create a calorie deficit.
A simple counterexample illustrates this: if you binge eat excessively during the eight-hour eating window, consuming more calories than your daily needs, then intermittent fasting will not only fail to make you lose weight but might even cause you to gain weight.
Intermittent fasting itself doesn't possess any special fat-burning magic; it's merely a tool to help you control calorie intake. Treating this tool as a miraculous cure is the biggest problem.
Intermittent Fasting Does Have Its Benefits, But Understand What They Are
Fasting indeed has additional benefits like improving insulin sensitivity and promoting cellular autophagy, but these cannot replace calorie management.
After clarifying that "calorie deficit is the core," other benefits of intermittent fasting can be viewed more objectively. Based on existing research and Coach Kai's summary, the known benefits of intermittent fasting include:
- Improved Insulin Sensitivity: Reduced insulin secretion during fasting periods helps stabilize blood sugar long-term, making the body less prone to storing fat.
- Improved Blood Lipids and Lowered Blood Pressure: Provides a certain auxiliary effect for groups at risk of cardiovascular diseases.
- Promoted Growth Hormone Secretion: Growth hormone helps support muscle retention and reduce fat, being one of the important hormones for improving body composition, though it does not completely prevent muscle loss for everyone.
- Initiation of Autophagy: This is the body's self-renewal mechanism, helping to clear old cells, reduce inflammation, and slow down aging.
- Reduced Chronic Inflammation: Chronic inflammation is the root of many diseases, and fasting helps prevent it.
These benefits are real, but they are added values of intermittent fasting, not a reason for people to "lose weight without managing calories."
Potential Risks of Intermittent Fasting: Fitness Enthusiasts Must Pay Special Attention
Fitness enthusiasts must be particularly vigilant about three major risks: insufficient protein intake, decreased metabolic rate, and nutritional imbalance.
For the average person, the risks of intermittent fasting might be relatively limited; however, for serious fitness enthusiasts, several potential issues must be addressed.
Risk One: Insufficient Protein and Calorie Intake, Affecting Muscles
A shortened eating window means that the difficulty of consuming adequate protein increases. Protein is the raw material for muscle synthesis, and prolonged insufficient intake increases the risk of muscle loss.
If overall calorie intake remains too low for an extended period, the body enters a catabolic state, potentially starting to break down muscle for energy. The real risk lies in prolonged insufficient protein and total calorie intake due to fasting—which was one of the key reasons Coach Kai failed during his muscle-gaining phase when doing 16:8.
Risk Two: Decreased Basal Metabolic Rate
Muscle mass is a significant support for the basal metabolic rate. Once muscles are lost due to chronic insufficient nutrient intake, the basal metabolic rate will also decrease.
What's more troublesome is that when the body is in a prolonged calorie deficit, it activates a "starvation protection mechanism," automatically lowering the metabolic rate to reduce energy consumption. This is why many people who diet often regain weight quickly once they stop—their metabolism has already been suppressed.
Risk Three: Nutritional Imbalance
A shortened eating window also increases the difficulty of consuming a balanced range of nutrients within that limited time. Vegetables, fruits, vitamins, minerals, essential amino acids—these might all be sacrificed in the rush to "finish eating calories."
"Will Fasting Cause Muscle Loss?" — Debunking the Most Common Fear
Short-term fasting does not directly burn muscle; weight loss is mostly due to water and glycogen depletion. To confirm, body composition should be measured.
Short-term fasting itself does not directly cause muscle loss; this is physiologically based. The body's energy usage order does not immediately burn muscle upon fasting.
The body will first use stored glycogen, then fat. It takes several days of fasting for muscle tissue to truly be broken down. Typical 16:8 or alternate-day fasting is far from reaching this threshold.
Additionally, the body secretes growth hormone during fasting, one function of which is to help preserve muscle. However, this doesn't mean protein intake can be completely ignored—fasting itself doesn't harm muscles, but prolonged insufficient protein and calorie intake is the real risk. These are different levels of issues and should not be confused.
As for many who say, "My weight dropped after fasting, did I lose muscle?"—Not necessarily. The weight lost during fasting mostly comes from water and glycogen, both of which have weight. A decrease in body weight is a normal physiological response and does not mean muscle tissue itself has been consumed.
If you want to confirm whether you lost fat or muscle, Coach Kai recommends using an InBody scan to measure body composition, or using a tape measure to track waist, hip, and arm circumference. Both methods are more accurate and meaningful than simply looking at body weight numbers.
You Can Still Train During Fasting, But There Are Things to Do Right
You can train fasted, but performance will decrease. It's recommended to schedule your eating window after your workout.
The most common question from fitness enthusiasts practicing intermittent fasting is: "Can I work out while fasting?" Yes, you can, but be prepared: in a fasted state, your body's glycogen stores are lower, and training performance will typically be worse than in a fed state. This is a reality that needs to be accepted.
⚠️ Safety reminder: If you experience severe dizziness, palpitations, or lightheadedness during fasted training, you should immediately stop training and eat something; if symptoms do not improve, seek medical attention promptly, do not push through.
Coach Kai's implementation suggestions are as follows:
- Consider supplementing with amino acids before training: Some views suggest that supplementing with BCAA (branched-chain amino acids) can provide some protection during fasted training, but it should be noted that BCAAs contain calories and may trigger an insulin response, so whether they affect the fasted state is currently debated. If you want to reduce the risk of catabolism during fasted training, supplementing with EAA (essential amino acids) or complete proteins might be a more comprehensive option, assess based on individual circumstances.
- Schedule your eating window after your workout: If you usually train in the morning, you can set your eating window to start after your workout. For example, if you train at 8 AM, your eating window would start at 9 AM or 10 AM. Muscles have a stronger absorption capacity after training, so supplementing protein at this time can lead to better muscle synthesis results.
What to Do About Dizziness, Weakness, and Nausea in the Early Stages of Fasting?
Dizziness and weakness in early fasting are often due to low blood sugar or electrolyte imbalance; supplementing water and salt can help. Severe symptoms require medical attention.
These symptoms usually result from low blood sugar or an imbalance of electrolytes and are common in people just starting intermittent fasting because the body is not yet accustomed to prolonged fasting.
Coach Kai's advice: During fasting, it is crucial to drink plenty of water (fasting means not consuming caloric food, not not drinking water; dehydration will put an additional burden on the body) and you can add a small amount of salt to your water to replenish electrolytes. You can also drink unsweetened tea or black coffee to help get through the fasting period. Mild discomfort during adaptation usually subsides as the body gradually adjusts.
⚠️ Safety reminder: If symptoms persist, worsen, or if you experience disorientation, persistent vomiting, or other severe discomfort, stop fasting immediately and seek medical attention. Do not endure it on your own. Mild transitional discomfort and severe symptoms requiring medical attention are different and should not be confused.
How Should a Fasting Beginner Start? Gradually, from 12:12
Beginners should start with 12:12 fasting to allow the body to adapt, then gradually progress to 16:8.
Another reason for Coach Kai's failure was that he directly challenged 16:8 on his first attempt, giving his body no adaptation period. For beginners, he explicitly advises: start with 12:12 intermittent fasting.
Fasting for 12 hours and eating for 12 hours daily is far less challenging for the body than 16:8 and easier to adapt to. Once the body gets used to the fasted state, then gradually progress to 16:8, or even higher-intensity fasting methods.
Gradual progression isn't because you lack willpower, but because your body needs time to learn how to function normally without food supply. This adaptation process cannot be skipped; forcing it will only make you give up faster.
Intermittent Fasting Isn't for Everyone; These Groups Should Consult a Professional First
Pregnant women, diabetics, and individuals with a history of eating disorders, among other specific groups, must consult a professional before undertaking fasting.
Coach Kai specifically points out that intermittent fasting is not suitable for everyone. The following groups should consult a doctor or nutritionist for professional advice before attempting any fasting plan:
- Pregnant women
- Breastfeeding mothers
- Adolescents
- People with diabetes
- Individuals with a history of eating disorders: The dietary restrictions and feeling of hunger associated with fasting may exacerbate related psychological symptoms or trigger old behavioral patterns. It is crucial to only consider this under the joint assessment of a professional psychologist and physician, and not to attempt it on your own.
If you try intermittent fasting and find it's truly not for you, there's absolutely no need to be disheartened. There are many ways to lose fat, and the most important thing is to find a method that is safe, sustainable long-term, and truly suits you.
AROAK Hardcore View: The Correct Place of Intermittent Fasting
Intermittent fasting is merely a tool for calorie control. Safety, sustainability, and suitability for oneself are the only criteria for judging whether a diet is good or bad.
Integrating all information, Coach Kai's overall positioning of intermittent fasting is very clear: intermittent fasting is a tool to help control calorie intake; it is not a magic weight loss pill, nor is it a universal solution applicable to everyone.
If intermittent fasting helps you naturally control calorie intake and makes your diet more regular, then it's worth trying. But if it causes you suffering, makes you binge eat uncontrollably during your eating window, or prevents you from consuming enough calories and protein during your muscle-gaining phase—then it's not the right tool for you, and there's no need to force yourself.
Frequently Asked Questions
What is the principle behind intermittent fasting for fat loss?
Intermittent fasting helps with fat loss based on one core principle: calorie deficit. Shortening the eating window makes it easier to reduce total calorie intake, thereby creating a calorie deficit. Fasting itself has no special fat-burning magic; if you binge eat beyond your daily caloric needs during the eating window, you will still not lose weight.
Will intermittent fasting cause muscle loss?
Short-term fasting itself does not directly cause muscle loss. The body's energy usage hierarchy is to first deplete glycogen, then burn fat; muscle tissue would only be broken down after several days of fasting. The real risk lies in prolonged insufficient protein and total calorie intake, which are different issues and should not be confused.
Can I train during fasting?
Yes, but in a fasted state, the body's glycogen stores are lower, and training performance is usually worse than when fed. Coach Kai suggests considering amino acid supplementation before training and scheduling your eating window after your workout to take full advantage of muscles' enhanced absorption capabilities post-training. If you experience severe dizziness, palpitations, or lightheadedness during training, stop immediately and eat something.
How should a fasting beginner start?
Coach Kai recommends starting with 12:12 intermittent fasting, which means fasting for 12 hours and eating for 12 hours daily. This is far less challenging for the body than 16:8 and easier to adapt to. Once the body gets used to the fasted state, gradually progress to 16:8 or higher-intensity fasting methods; do not attempt high difficulty levels from the start.
Who should not try intermittent fasting?
Pregnant women, breastfeeding mothers, adolescents, people with diabetes, and individuals with a history of eating disorders should consult a doctor or nutritionist for professional advice before attempting any fasting plan. Those with a history of eating disorders need to be especially cautious and should only consider it under the joint assessment of a professional psychologist and physician.
The content of this article is excerpted from videos on "Coach Kai's" YouTube channel. Training advice is for reference only; if you have physical discomfort or injury issues, please consult a professional physician or physical therapist.
