Let's Start with a Failure
Coach Kai personally tried and failed at 16:8 intermittent fasting. The reasons for his failure are traceable and are blind spots that most people overlook.
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 almost half a day between waking up and 2 PM when he couldn't eat. The result: he felt scattered, irritable, and would uncontrollably overeat once the eating window opened.
Even more challenging, his goal at the time was to gain muscle, which required a considerably high intake of calories and protein daily. To consume the total calories needed for muscle gain within an eight-hour window, he almost exclusively relied on high-calorie foods, feeling overly full every time, and eventually gave up.
This experience is not meant to scare you, but rather, Coach Kai's subsequent analysis clearly identified the root causes of his failure—and these reasons are precisely the blind spots that many people completely overlook when doing intermittent fasting.
What is Fasting? Let's First Understand the Types
Intermittent fasting comes in three types: 16:8, 5:2, and alternate-day. The core of all of them is restricting the eating window.
The core concept of intermittent fasting is simple: it's not about not eating at all, but about eating within a specific time window and remaining fasted the rest of the time.
Currently, there are three main types of fasting 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: Within a seven-day week, eat normally for five days and follow a very low-calorie diet for two days. These two days are typically not consecutive, such as Monday and Thursday. Specific calorie intake recommendations should be evaluated by a dietitian based on individual circumstances.
- Alternate-Day Fasting: Eat normally one day, then follow a very low-calorie diet the next day, and alternate.
These three methods each have their own difficulties and适用 situations, but one thing is common: their essence is the same.
Debunking the Myth: The Real Reason Intermittent Fasting Aids Fat Loss Is Not "Fasting" Itself
The only reason intermittent fasting helps with fat loss is a calorie deficit; fasting itself has no special fat-burning magic.
Many people, upon hearing that intermittent fasting can aid weight loss, consider this method miraculous, as if merely shortening the eating time will automatically burn fat. This perception needs to be directly corrected.
The fundamental principle behind why intermittent fasting helps with fat loss is singular: 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 compulsively overeat during the eight-hour eating window, consuming more than your daily caloric needs, then not only will intermittent fasting not lead to weight loss, but it might even cause weight gain.
Intermittent fasting itself has no special fat-burning magic; it is merely a tool to help you control your calorie intake. Treating this tool as a panacea is the biggest problem.
Intermittent Fasting Does Have Its Benefits, But You Need to 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," the other benefits of intermittent fasting can be viewed more objectively. According to existing research and Coach Kai's compilation, the known benefits of intermittent fasting include:
- Improved Insulin Sensitivity: Insulin secretion decreases during fasting, which helps stabilize blood sugar in the long run, making the body less prone to storing fat.
- Improved Blood Lipids and Lower Blood Pressure: Has a certain辅助 effect for groups at risk of cardiovascular disease.
- Promotes Growth Hormone Secretion: Growth hormone helps support muscle retention and reduce fat, being one of the important hormones for body composition improvement, but it does not fully prevent muscle loss for everyone.
- Initiates Cellular Autophagy: This is the body's self-renewal mechanism, helping to clear old cells, reduce inflammation, and slow down aging.
- Reduces Chronic Inflammation in the Body: Chronic inflammation is the root of many diseases, and fasting helps prevent it.
These benefits are real, but they are additional values of intermittent fasting, not a reason 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 may be relatively limited; however, for serious fitness enthusiasts, there are several potential issues that must be addressed.
Risk One: Insufficient Protein and Calorie Intake, Leading to Muscle Impact
A shortened eating window means that the difficulty of consuming enough protein increases. Protein is the raw material for muscle synthesis, and if intake is consistently insufficient, the risk of muscle loss will increase.
If overall calorie intake also remains too low, the body enters a long-term catabolic state, which may begin to break down muscle for energy. The real risk lies in long-term protein and total calorie deficiency caused by fasting—this was one of the key reasons Coach Kai failed at 16:8 during his muscle-gaining phase.
Risk Two: Decreased Basal Metabolic Rate
Muscle mass is a significant support for the basal metabolic rate. Once muscle is lost due to chronic insufficient nutrient intake, the basal metabolic rate will also decrease.
Even more problematic, when the body is in a chronic calorie deficit, it activates a "famine protection mechanism," automatically lowering the metabolic rate to reduce energy consumption. This is why many people who diet eventually regain weight quickly once they stop—their metabolism has already been suppressed.
Risk Three: Nutritional Imbalance
A shortened eating window concurrently increases the difficulty of consuming balanced nutrients within a limited time. Vegetables, fruits, vitamins, minerals, essential amino acids—these may all be sacrificed in the rush to "finish eating calories."
"Will Intermittent 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 based on physiological evidence. The body's energy usage hierarchy does not immediately burn muscle upon fasting.
The body will first use stored glycogen, then fat, and it must fast for several days before truly breaking down muscle tissue. Typical 16:8 or alternate-day fasting is far from reaching this threshold.
Additionally, the body secretes growth hormone during fasting, one of its functions being to help preserve muscle. However, this does not mean protein intake can be completely ignored—fasting itself does not harm muscle, but long-term insufficient protein and calorie intake is the real risk. These are different levels of issues and should not be confused.
As for many people who say, "I lost weight after fasting, is it muscle loss?"—not necessarily. The weight lost during fasting mostly comes from water and glycogen; both have weight, so 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're losing fat or muscle, Coach Kai recommends using an InBody scan to measure body composition, or measuring various body parts like waist, hip, and arm circumference with a tape measure. Both methods are more accurate and meaningful than simply looking at the scale number.
You Can Still Train During Fasting, But There Are a Few Things to Do Right
Training while fasted is possible, 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 train during fasting?" Yes, you can, but be prepared: in a fasted state, the 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, stop immediately and eat. 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 believe that supplementing with BCAA (branched-chain amino acids) can provide some protection during fasted training, but it's important to note 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 protein might be a more comprehensive option, and it's recommended to evaluate based on individual circumstances.
- Schedule your eating window after training: If you typically train in the morning, you can set your eating window to begin after your workout. For example, if you train at 8 AM, your eating window could start at 9 AM or 10 AM. Muscle absorption capacity is stronger after training, so supplementing protein at this time can lead to better muscle synthesis effects.
What to Do if You Feel Dizzy, Weak, or Nauseous During the Initial Stages of Fasting?
Dizziness and weakness during early fasting are often due to low blood sugar or electrolyte imbalance. Hydration with salt can help; severe symptoms require medical attention.
These symptoms usually stem from low blood sugar or an electrolyte imbalance and are common in people just starting intermittent fasting, as the body is not yet accustomed to prolonged fasting.
Coach Kai's advice: During fasting, it is crucial to drink adequate amounts of water (fasting means not consuming caloric food, not abstaining from water; dehydration will place 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 gets used to it.
⚠️ Safety reminder: If symptoms persist or worsen, such as 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 Progress from 12:12
Beginners should start with 12:12 fasting to allow the body to adapt, then gradually progress to challenging 16:8.
Another reason for Coach Kai's failure was that he directly challenged 16:8 on his first attempt, giving his body no time to adapt. For beginners, he clearly advises: start with 12:12 intermittent fasting.
Fasting for 12 hours and eating for 12 hours each day is far less challenging for the body than 16:8, making it easier to adapt. Once the body gets used to the fasted state, you can gradually progress to 16:8, or even more intense fasting methods.
Gradual progression isn't because you lack willpower, but because your body needs time to learn to function normally without food. This adaptation process cannot be skipped; trying to skip 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 attempting fasting.
Coach Kai specifically points out that intermittent fasting is not suitable for everyone. The following groups should consult a doctor or dietitian 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 consider implementing fasting only after a joint assessment by a professional therapist and physician, and self-attempting is not recommended.
If you try intermittent fasting and find it's genuinely not for you, there's absolutely no need to be discouraged. There are many ways to lose fat, and the most important thing is to find a method that is safe, sustainable in the long term, and truly suits you.
AROAK's Hardcore View: The Correct Place for 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 dietary approach is good.
Integrating all the information, Coach Kai's overall positioning of intermittent fasting is very clear: intermittent fasting is a tool to help control calorie intake, not a magic bullet for weight loss, nor a universal solution suitable for everyone.
If intermittent fasting helps you control your calorie intake more naturally and makes your diet more regular, then it's worth trying. But if it causes you pain, leads to uncontrolled binge eating during your eating window, or prevents you from consuming enough calories and protein during your muscle-building 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 through 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 overeat during the eating window and exceed your daily calorie needs, you still won't lose weight.
Will intermittent fasting cause muscle loss?
Short-term fasting itself does not directly cause muscle loss. The body's energy usage sequence is to first deplete glycogen, then burn fat; muscle tissue is only likely to be broken down after several days of fasting. The real risk lies in long-term 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, so training performance is usually worse than in a fed state. Coach Kai suggests considering supplementing with amino acids before training and scheduling the eating window after training to take full advantage of the increased muscle absorption capacity post-workout. If severe dizziness, palpitations, or faintness occur during training, stop immediately and consume food.
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 each day. This is much less challenging for the body than 16:8 and easier to adapt to. Once the body gets used to the fasted state, you can gradually progress to 16:8 or more intense fasting methods; do not attempt high-difficulty fasting 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 dietitian for professional advice before attempting any fasting plan. Those with a history of eating disorders need to be especially cautious and should only consider fasting after a joint assessment by a professional therapist and physician.
The content of this article is excerpted from videos on the "Coach Kai" YouTube channel. Training advice is for reference only; if you experience physical discomfort or pain, please consult a professional doctor or physical therapist.
