Can You Lose Weight By Not Eating?

Can You Lose Weight By Not Eating?

It seems as though every week there is a new “miracle” diet in the fitness world. From the ones that have stood the test of time such as the Atkins diet, to the new “magical” butter-in-your–coffee, detox tea’s, and juice cleanse diets. But, what about a plain and simple “can you lose weight without eating” diet? Is this possible?

Simply put, yes, it is possible to lose weight without eating and here’s why. Although human nutrition is an incredibly complex subject to understand, perhaps the easiest concept to wrap your mind around and the most important factor for the purpose of weight loss, is calorie balance. Don’t even worry about trying to understand what exactly a calorie is; just know that it’s a unit of energy, and that in order to lose weight you need to burn more of them than you consume through food. On the other hand, if you take in more calories than you burn, you will gain weight. For the math-minded, this is the equation:

Calories consumed – calories burned = weight gain (if positive number); weight loss (if negative number)

With this knowledge and using the equation above, you can see that not eating anything would make the input of “calories consumed” equal zero. Additionally, the input of “calories burned” would always be a number much higher than zero, which would put the output of the equation (weight change) into a negative number. Let’s see how this looks in the equation above assuming your calories burned is 2000.

Calories consumed (0) – calories burned (2000) = -2000 total daily net calories (weight loss)

Given this example, you can see that your total daily net calories would be a large negative number. A consistent negative number over a period of time will inevitably cause weight loss. So, again, yes you can lose weight by not eating. However, this is an example of an extreme caloric deficit. Not only will such a large negative calorie balance cause nutrient deficiencies over time, but it will not be ideal for your body composition or your success long-term.  A large deficit not being ideal for weight loss may be a hard concept to grasp, especially because we are conditioned to think that if a little bit of something works, then more of that something must be better. This is not the case with caloric intake.  With that being said, yes, you do need a caloric deficit to lose weight, but a deficit of 500-1000 calories is ideal. To be clear, a calorie deficit is referring to eating less calories than it takes to maintain your weight. Therefore, to know how many calories you need consume in order to be in a deficit, you must first know how many calories it takes to maintain your weight.


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How many calories should I have per day to lose weight?

Perhaps the king of weight loss questions, and rightfully so, is “how many calories should I consume to lose weight?” It is important to understand that every person is different and needs to take into consideration their unique body and lifestyle when determining proper caloric intake. Just because a friend or family lost weight at a given calorie count doesn’t automatically mean it is the right number for you. With that being said, it is important to understand how many calories you burn in order to understand how many calories you should consume.  Things to consider are factors such as: age, gender, height, weight, physical demand of job, intensity/duration of daily exercise, and body fat percentage.  Let’s take a brief look at the 3 components that make up your total daily energy expenditure (TDEE ).

  1. Basal Metabolic Rate (BMR) - The BMR is the minimal number of calories YOUR body needs to sustain life at a resting state. Whether you’re very active or sedentary, BMR will account for the greater portion (60-75%) of the calories you burn in 24-hour period. Furthermore, BMR is directly correlated with lean body mass. That is, the more lean body mass you have, the higher your BMR will be and vice versa. This is due to the fact that muscle tissue is a more metabolically demanding tissue than fat. In other words, the more muscle you have on your body, the more calories you will burn even when you are just sitting around.

  2. Physical Activity- Your physical activity will have the second largest impact on your total daily energy expenditure, consisting of about 20-35% of your calories burned in a 24-hour period. Simply put, the more you move your body the more calories you will burn.

  3. Thermic Effect of Food (TEF)-  The TEF refers to the number of calories the body must use in order to digest the different macronutrients (fat, carbohydrates, and protein). For example, if you were to eat 100 calories of fat, it would take 1-3% of those 100 calories to digest the fat. For carbohydrates, it would take 8-12% of those 100 calories and for protein 20-30% of those 100 calories. TEF accounts for 5-10% of your total daily energy expenditure.

There are several tools and equations that do a great job at giving accurate caloric intake. A popular equation used even in clinical settings is the Mifflin St. Jeor formula which is linked below. Thankfully, instead of doing the tedious math yourself, there are handy calculators like this one ( to speed up the process. Try it out for yourself! Remember, finding an accurate number of calories to consume is important for body composition and long-term success.


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Is weight loss and fat loss the same?

People tend to think of these two phrases synonymously. However, there is a distinct difference between the two phrases. Understanding this difference can make a significant impact on how you approach your weight loss journey, and also on how good you will look naked standing in front of the mirror when the journey is over.

First, let’s understand the concept of just straight weight loss. Let’s use an example to illustrate this. One Monday you stand on the scale and you weigh 150 pounds. You decide that for the next 7 days you will not eat anything. The following Monday you step on the scale and weigh 140 pounds. Wow! Amazing right? You just lost 10 pounds of fat!... or did you? Unfortunately, this is not the case. What may appear like a 10 pound loss of pure fat in just one week is actually a combination of fat, water, glycogen (carbohydrates stored in your muscle), and muscle. Sure, 10 pounds of weight was lost, but this is not to be confused with 10 pounds of fat loss. Is this ideal to lose this much weight by not eating? The answer is no. Let’s face it; what we all really want is fat loss, not just weight loss at the expense of not eating and feeling awful. If we exclusively focus on weight loss by virtue of going on a very low or zero calorie diet, we also risk breaking down muscle tissue.  So, what does this mean? This means that although weight was lost and we will be smaller in the sense that physically we will take up less space, we won’t necessarily look more “toned”, because of the fact that we consistently loss muscle along with fat. In other words, you will still look similar to how you did before the weight loss as far as body composition goes, just a smaller version. This is why focusing on fat loss is the best way to approach a weight loss journey. Here are some tips to maximize fat loss:

·         Incorporate weight training - There is no better way to speed up your metabolism than putting on some lean muscle. This extra muscle burns more calories just by sitting there!


·         Perform High Intensity Interval Training (HIIT). Aerobic exercise is a good way to burn calories and fat, but to maximize your body's fat-burning power; you want to include high-intensity interval training, or HIIT. This type of exercise alternates between periods of fast-paced exercise, followed by a slower pace for a defined period of time.


·         Eat a high-protein diet- Protein takes the most energy to digest. You will burn more calories digesting protein than carbs or fats. It is also helps with staying full longer and plays a significant role in maintaining muscle mass.


·         Limit alcohol to 1 drink per day for women and 2 for men. When you consume alcohol, your body preferentially burns it as fuel instead of body fat.


·         Be in a slight caloric deficit- Eating fewer calories than your body needs forces your body to burn fat for fuel. Reducing the number of calories you need to maintain your current weight by 500 to 1000 calories a day promotes a 1- to 2-pound weekly weight loss. For example, if you need 2,400 calories a day to maintain your weight, maximize fat loss by limiting your intake to 1,400 to 1,900 calories a day


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How many LBS should I lose per week?

First and foremost, let’s be clear that the answer to this question is not completely black and white. The degree of weight loss per week can range and is dependent on your starting weight (the more you weigh the more you can lose) and your individual goal i.e. do you care about retaining muscle or do you just want to hit a number on the scale at any expense? For the most part, however, there is a common misunderstanding that the more weight you lose in a week, the better off you are. Instead, aim to lose 1-2 LBS per week.  Losing more than 1-2 pounds per week greatly increases the chances your body will break down muscle tissue.  As mentioned previously, this is not ideal for body composition. It is also not ideal for long-term success; because the more muscle you have, the more calories you ultimately burn. Plus, you will look and feel better losing weight slowly but surely.


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How do I set myself up for long-term success?

This may be the single most under-asked, yet critical question there is in terms of weight loss. People tend to focus on short-term, rapid weight loss which causes them to fail to properly set themselves up for success long-term. Instead, they catch themselves trapped in the vicious cycle of losing weight quickly, only to regain that weight right back. If that sounds like your dieting history, you are not alone. In fact, most people who have lost a significant amount of weight will have regained it all back and sometimes with interest. Here are 5 ways to set yourself up for success long-term

Be realistic. It is important to be honest and realistic about how long you might be able to eat a certain way. Many of us lose weight on a popular diet that is far too restrictive. This leads to feeling frustrated, fatigued, and malnourished. Ultimately, this brings us to a state of binging and returning back to our old ways of eating. When choosing a diet, make sure you can see yourself doing it forever. Can you really not eat anything forever?


Eat foods you love. The importance of calorie control for weight loss was discussed earlier; however, the foods that make up those calories is essential as well. “The best diet” phrase is commonly used by large companies trying to market their diet or product. The truth is that there is no such thing of “the best diet”. The best diet is the diet that you can adhere to and enjoy long-term.  Think about it, wouldn’t you be more likely to stick to a diet if you are eating foods you actually love?  


Give yourself a break. Having a piece of cake or some pizza doesn’t mean your weight loss is sabotaged and you have to start over. It’s really important to have a long-term mindset and remember that weight gain happens over a long period of time, not over one piece of cake. Focus on being in a calorie deficit on most days, but if it happens where you go over one day, no big deal. Start again tomorrow!


Start high.  As you lose weight, the amount of calories you can consume to maintain your weight will drop. This means that to lose more weight, you will need to consume fewer calories as you go. The goal should be to eat as many calories possible while still losing fat. There is no point in starting your weight loss diet at 1200 calories when you can lose fat at 1800 calories.


Patience and Consistency.  A weight loss journey is the one race where you want to be a turtle- slow and steady wins the race. Remember, weight loss is a marathon not a sprint. Try to picture yourself one, two, or even three years down the road. Many times people get caught up in wanting a huge change over a period of weeks. It didn’t take most people weeks to get to the weight they are now, so don’t expect it to take weeks to get back to the weight you desire to be.


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What about Intermittent Fasting?

Now that you know that losing weight by not eating at all is not the ideal approach, what about intermittent fasting? Intermittent fasting is a term that can mean many things, but the main concept is that the diet involves periods of fasting (consuming no calories) and eating (consuming calories). One of the most common types of intermittent fasting is called Time-Restricted Feeding; where you consume all of your calories in designated hours each day. For example, 11AM-7PM is a popular 8 hour “feeding window” protocol. This would then be followed by a 16 hour fasting period.

This can be a useful tool for people who may naturally feel less hungry in the mornings, or for people who like a more simplified structure to their eating. Fasting has been used for thousands of years in different cultures for different reasons, but any research on intermittent fasting for weight loss is in its beginning stages. If anything, intermittent fasting may make calorie control easier by simply allowing you less time in the day to eat. If intermittent fasting is something you want to try and it fits into your lifestyle, go for it! But remember, there is nothing magical about it and you will still need to be in a daily caloric deficit to lose weight. You can learn more about intermittent fasting by reading my blog "Intermittent fasting and weight loss: does it work?".

Bottom line: Losing weight by not eating will indeed cause weight loss. However, it is not the ideal approach for body composition, long-term success, or to supply your body with the nutrients it needs. Finding the appropriate caloric intake for you is critical to your long-term success on a weight loss journey. Aim to lose 1-2 pounds weekly in order to retain as much muscle mass as possible. Focus on long-term success instead of losing weight quickly, as this commonly causes a rebound effect and puts you right back to where you started. Lastly, intermittent fasting is a great tool if you find yourself already not hungry during large portions of the day. Don't forget to enjoy your weight loss journey!


Intermittent fasting and weight loss: Does it work?

Intermittent fasting and weight loss: Does it work?

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