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Intermittent Fasting for Fat Loss: How powerful is it?

Intermittent fasting is a powerful method for fat loss while preserving muscle mass. Read on to learn more.
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Many people want to lose weight, but what they mean is that they want to lose fat. Unfortunately, most calorie-restricted diets result in muscle loss. Intermittent fasting is an excellent method to lose fat while preserving muscles.

Written by
Christine Richardson, PhD
Clinical Project Manager at Becton Dickinson

There are many strategies you can try to lose some unwanted fat. For example, maybe you or a friend have tried a popular diet like Whole 30 or Paleo…or maybe this is the first time you’ve decided to try a diet. 

Either way, looking for the most effective diet that’s the easiest to turn into a habit is HARD! There are so many articles, websites, books, etc. written on this exact topic. Some are rooted in science and some…well, aren’t scientifically-founded.

One dietary strategy that has become popular recently is intermittent fasting. One of the reasons why intermittent fasting has become popular is because it works! 

In this article, we’re going to explain how intermittent fasting is an effective dietary strategy for fat loss.

Weight vs Fat Loss

Many of us say we want to lose some weight but what most of us mean is that we want to lose fat. And yes, there’s a big difference.

Losing weight simply means that the number you see on the scale has gotten smaller. What that number doesn’t tell you is what you’ve lost. Losing weight can oftentimes be misleading because it can be a result of losing body water or muscle mass.

Losing body water happens all of the time. For example, you lose body water when you perspire or urinate. This can affect your weight but once you rehydrate, your weight will go back to where it was. 

Many people lose muscle mass when one a diet. This isn’t an ideal situation because muscles burn a lot of energy. This means that losing muscle mass will decrease the amount of calories you burn each day. Over time, this can lead to you eating more than you burn, which leads to an increase in body fat.

Losing fat means exactly what it suggests – decreasing your body fat percentage. No matter what weight loss strategy you are using, losing fat mass should be the goal.

Caloric Restriction and Fat Loss

A calculator, a red note book and a pen.

The most common strategy to lose weight (or fat) is restricting calories. Unfortunately, long-term caloric restriction can cause a lot of undesirable side effects including weight-loss plateaus, fat regain when eating normally again, changes to hormonal pathways, decreased bone density, and loss of muscle mass (1, 2, 3, 4).

This doesn’t sound good, does it? 

Intermittent Fasting for Fat Loss

Now that we’ve discussed some of the cons to caloric restriction, you’re probably wondering if intermittent fasting is a good strategy that won’t cause some of those undesirable side effects we just mentioned. And the short answer is yes, it definitely can be a better option! 

Intermittent Fasting Improves Overall Health

For starters, intermittent fasting has been shown time and time again to help better your health. It can decrease the risk of cardiovascular disease, insulin resistance, decrease inflammation, and more (5, 6, 7, 8, 9). 

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Intermittent Fasting Increases Metabolic Flexibility

Flexibel woman doing a deep stretch.

The reason fasting may be a superior choice to caloric restriction for fat loss is because intermittent fasting helps you become more “metabolically flexible” or “metabolically efficient.” What does this mean? The term “metabolic flexibility” is just a fancy way of saying that your body is more efficient at using your fat stores for fuel as opposed to your stored sugar. 

In order to achieve this, you have to train your body. The best way to train your body is to fast for a certain period of time (12+ hours) so that your body loses most of its stored sugar (glycogen). When this occurs, your body will turn to its fat stores for energy. 

Some scientists refer to this shift as “flipping the metabolic switch”(10). After doing this for a while, your body becomes better trained at using certain metabolic pathways to use fat for fuel…ones that your body may not be using much right now. When your body is better trained for using more fat throughout the day-that’s when you’re more metabolically flexible.

When you teach your body to use more stored fat for fuel, you are really training it to make use of your fat stores. This means that your body will be using more fat for energy no matter what you’re doing – watching TV, walking, exercising, etc. 

People who are more metabolically flexible tend to be leaner individuals with lower body fat percentages (11, 12). Metabolic flexibility also appears to be something that your body can sustain long-term, meaning that it won’t just go away if you decide to stop intermittent fasting.

Training your body to be more metabolically flexible has been shown to be not only effective for weight loss but studies show that people who are more metabolically flexible are at a lower risk of developing certain diseases (13, 14).

Scientists believe that this is part of the reason why your body may not lose muscle mass while fasting. Your muscles also have some stored fat and this fat can be used for energy by your muscles if you’re exercising and/or moving around. If your body isn’t well-trained to use fat, your body can and will break down your muscles for energy, if needed (10, 15). 

Intermittent Fasting Stimulates Growth Hormones

Another reason why your body may not lose muscle mass while fasting is because fasting increases the levels of human growth hormone. This hormone also helps your body burn more fat while preserving muscle mass (16, 17).

In Summary

Weight loss isn’t the same as fat loss. Losing fat while maintaining muscle mass should be the goal when starting a new diet.

You might be interested in reading our other articles about fasting and loose skin, as well as how to get rid of face fat with intermittent fasting, fasting and cellulite or stress as a reason for weight loss.


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