Intermittent Fasting and Your Metabolism: Should Someone with a Slow Metabolism Try Intermittent Fasting?

by Dr. David Minkoff March 11, 2021 4 min read

Athletic stomach of a person with a large body of water behind them.

Intermittent fasting has become increasingly popular over the last couple of decades, and many people are curious whether it is right for them.

Those who believe they have a “slow” metabolism are especially concerned that any form of fasting might further slow the metabolism, leaving them feeling groggy or less energetic, not to mention hungry.

Surprisingly, this couldn’t be further from the truth.

Intermittent fasting can improve your metabolism while helping you lose weight, along with a slew of other health benefits.

Now, before you reject this out of hand as hype or a fad, let’s dive into some of the details.

Understanding Your Metabolism

According to the Encyclopedia Britannica, metabolism is defined as:

“the sum of the chemical reactions that take place within each cell of a living organism and that provide energy for vital processes and for synthesizing new organic material.”

When we’re talking about a person’s “metabolism,” we are specifically referring to the cellular action of burning fat, sugar, or other substances to produce energy while at rest.

You may know people who can apparently eat whatever they want, all the time, and remain thin – while others carefully watch their diet, and yet somehow they can’t lose stubborn fat.

But let’s look at this issue from a different perspective.

Your body is an engine that burns and utilizes nutrients to produce energy and sustain itself. It is designed to stockpile energy-burning material in the form of fat so that your body can keep going even at times when food is not available. In fact, the average human body can last between 8 and 21 days without food, with extreme cases reported of people lasting up to 40 days or longer – all because the body is designed to metabolize all possible stores to stay alive.

Put simply, when you eat more than your body burns, it stores the extra for a rainy day. When you eat less than your body burns, it burns reserves for energy.

If you look closely, you will find that those “skinny people who can eat anything” often eat much less than you would expect.

How to Measure Your Metabolism: Basal Metabolic Rate

Basal Metabolic Rate (BMR) is one of the most common and effective methodologies to measure your metabolism. It tells you how much energy is being consumed by your body at rest, and it is influenced by several factors, which include:

Quantity of lean body mass
Muscle mass
Quantity of stored fat
Activity level

Contrary to popular belief, the more you weigh, the faster your metabolism is. Additional weight means that your body has to work harder and burn more energy just to function – not the other way around.

[1]

There are several online calculators and formulas you can use to measure your BMR, but the only true way to measure it is through a professional who measures the oxygen output as you breathe while at rest.

Metabolism and Weight Loss

There is a fundamental flaw in many weight loss and “calorie-cutting” diet programs, and it has everything to do with your metabolism.

When you deprive your body of vital nutrients on a continuous basis, your body mounts a hormonal and physiological response to conserve energy by decreasing your BMR. To take an extreme example, you might have heard of the popular show The Biggest Loser. In this show, contestants lose anywhere from 100 to 300 pounds over seven months by cutting calories and eating a highly restricted diet along with exercise. Unfortunately, as the New York Timesreports, every single contestant put a large portion of that weight back on after their appearance on the show came to an end.

Why?

Because their bodies responded to their continuous fast by slowing down their metabolism. As soon as they resume a more regular eating pattern (even eating a healthier diet than they did before the show), their slower metabolism is burning less than they are eating. The math is simple – they are consuming more than they are burning.

[2,3]

And this brings us to one of the ultimate secrets for sustained, healthy weight loss regardless of whether your BMR is at an optimal level or not.

Intermittent Fasting Can BOOST Your Metabolism

While continuous, long-term nutrient deprivation will slow down your metabolism, intermittent fasting does the exact opposite.

Think about it – when you constantly eat throughout the day, your body is continually in glucose-burning mode while consuming the calories that you eat. It rarely (if ever) has a chance to switch to ketosis and start burning fat stores for energy.

When you go on an intermittent fasting program, you continue to provide your body with the nutrients it needs to survive while stimulating your body’s natural processes to utilize the stores built up over the years.

How does this work? According to modern science, there are two key factors in IF that improve your metabolism:

Your BMR is directly related to your muscle mass, body fat, and the ratio between the two. Typical weight loss regimens result in a loss of fat, a loss of muscle mass, and a loss of lean body mass – but weight loss with IF is different. Studies have consistently shown that those who participate in IF programs lose belly fat and overall body fat while retaining virtually all lean body mass – the ideal combination. This readjustment of your body weight has a direct and positive impact on your metabolism.
Intermittent fasting stimulates the production of natural norepinephrine. This hormone increases heart rate and blood flow while reducing blood pressure and directly improving your body’s ability to break down fat and metabolize sugar.

One study, in fact, found that a short fast can increase a man’s BMR by up to 14%!

[4,5,6]

The result? A wide range of health benefits, which include:

Increased loss of visceral fat
Increase in HGH (human growth hormone)
Decreased loss of lean body mass (which inevitably occurs as a result of weight loss)
Reduction of insulin levels and insulin resistance
Improvement in beneficial gene impressions
Reduce oxidative stress and inflammation
Improve risk factors of heart disease
Improved focus and energy levels

[7,8,9,10,11,12]

In Summary…

It is well worth your time to learn more about intermittent fasting, especially if you are looking to lose weight, keep it off, and feel energetic and alive.

Good luck!

References:

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*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.