Does Intermittent Fasting Slow Metabolism?

Does Intermittent Fasting Slow Metabolism?
Tim Börner

Tim Börner | Author

Tim Börner is a dedicated intermittent fasting advocate and user engagement specialist with a deep passion for promoting a healthy and balanced lifestyle. Based in Germany, Tim has been an integral part of the Fastic team for several years, where he combines his expertise in user engagement with his personal commitment to intermittent fasting. His approach is rooted in the belief that a harmonious blend of disciplined eating habits and mindful living is key to overall well-being.

You might be concerned about maintaining a healthy metabolism, especially after learning about recent findings. A 2021 study found that metabolism actually peaks earlier in life than previously thought and fluctuates throughout our lifetime. Searching for ways to ensure a healthy and optimal metabolism, you run into intermittent fasting.

With this information, one might wonder if intermittent fasting could potentially hurt metabolism. Continue reading to learn more and know whether or not fasting can mess up your metabolism.

Why Is Healthy Metabolism Important?

Good old metabolism, sometimes it can be our friend and other times our enemy. Metabolism is the functioning of multiple biochemical processes that convert food into energy. Metabolism fosters fundamental bodily functions such as digestion, breathing, and circulation. This intricate mechanism is vital for sustaining life and promoting essential tasks such as regulating energy production, cellular repair, and eliminating waste. 

The 2021 study found that metabolism peaks in infancy (the first year). Subsequently, it diminishes until the 20s, stabilizes until the 50s, and drops again after 60. This means that sustaining ultimate metabolism throughout different stages of life is necessary. 

What Is Intermittent Fasting?

Intermittent fasting consists of alternating eating and fasting periods throughout a 24-hour cycle. What is so attractive about fasting plans, compared to other approaches, is that no one regimen is best, they all work differently for each individual. Uncover how Fastic can help you and take the Fastic quiz to identify which fasting plan is best for you.

Fasting plans vary in various aspects, such as:

  • Calorie consumption: Some plans require a calorie limit while others allow you to eat as much as you desire during the eating window. The amount of calories you consume is determined by your objective, such as weight loss, building muscle mass, etc.

  • Eating window length: Eating windows can last as long as 12 hours or be as short as 4 hours. However, you don’t necessarily have to abide by the fasting hours, you can adapt the times to your preferences and objectives. 

  • Overall duration: Similar to the eating window length, the duration of the fast itself can be as short or long as you want. You can undergo the 20:4 fast for a week or a month, you have complete authority. 

Impact of Intermittent Fasting on the Body

What is the effect of fasting and eating periods on the body? During fasting hours, our metabolism turns on its “survival switch” to conserve energy. Null food intake can trigger ketosis, a metabolic state where the body burns fat for fuel instead of carbohydrates. Autophagy, the process of cellular renewal, can also be stimulated. Autophagy has been proven to promote longevity and disease prevention. 

Besides weight loss, intermittent fasting has plenty more benefits, including:

  • boost brain function which can help with brain fog

  • reduce inflammation decreasing risk factors for chronic diseases

  • promote blood sugar control by reducing insulin resistance

  • increase growth hormone secretion (key in metabolism)

How Does Intermittent Fasting Boost Your Metabolism?

A study of the effects of a 3-day fast on the body resulted in a 14% boost in the participants’ metabolism. How does this happen? While fasting, crucial metabolism hormones are secreted:

  • insulin,

  • human growth hormone (HGH), and

  • norepinephrine.

When insulin levels decrease during fasting, the body is prompted to switch its energy source from glucose to burning fat in a process called lipolysis. Lipolysis is the process of breaking down fat into fatty acids. After fatty acids have been broken down, they enter the bloodstream and are oxidized in tissues such as muscle cells, contributing to an elevation of metabolic rate. A lower metabolic rate means fewer burning of calories, whereas a higher metabolic rate results in more burning of calories.

Our body’s overall energy use affects how effectively it utilizes and processes nutrients from food, regulates weight, and maintains metabolic health.

does intermittent fasting slow metabolism

Does Intermittent Fasting Reduce Metabolism? What Do Studies Say? 

A study examining the effects of fasting periods lasting 12 hours, 26 hours, and 72 hours suggests that short fasting periods may increase metabolism. The resting metabolic rate, the total number of calories burned when the body is in complete rest, increased after 36 hours of fasting but returned to near baseline levels after 72 hours. Conversely, a study on Ramadan fasting proposes that weight loss strategies, like fasting, may slow down metabolism to adapt to low energy reserves due to diminished calorie intake. 

So, does intermittent fasting mess up your metabolism? Long-term fasting could temporarily reduce metabolism due to energy conservation. On the other hand, intermittent fasting for short periods can potentially increase metabolism during short-term fasting. 

What Causes Slow Metabolism? What Are the Signs?

Anyone can be a victim of a slow metabolism. Several factors that encourage it are:

  • Poor sleep and stress: Insufficient and poor quality sleep, and stress can lead to inadequate metabolism functioning.

  • Poor diet: Not sustaining a nutrient-dense diet, and consuming high-processed foods, sugar, and unhealthy fats can negatively affect metabolism. Track your meals and eating times, and select from fasting-friendly recipes to maintain a nutritious diet with the Fastic app.

  • Age: Metabolism slows down due to hormonal changes and decreased muscle mass. Intermittent fasting can benefit men over 40 by helping combat the effects of aging, and for women experiencing menopausal hormone fluctuations.

  • No physical activity: A decrease in muscle mass and activity levels affects metabolism.

  • Hormonal Imbalances: Individuals with hypothyroidism or polycystic ovarian syndrome (PCOS) use intermittent fasting to counteract symptoms.

Some signs of slow metabolism are:

  • digestive issues, such as constipation

  • dry skin and brittle hair (hair loss)

  • persistent fatigue

  • weight gain despite calorie restriction

  • difficulty losing weight even if exercising

  • irregular menstrual cycles

Which Intermittent Fasting Plan Has the Least Impact on Metabolism?

Saying a specific fasting protocol least impacts metabolism would be a complete lie. No two metabolisms are the same. What might not negatively impact one person might affect someone else. 

The way a fasting plan interacts with a body will depend on:

  • physical activity level

  • health conditions (if there are any chronic diseases to consider)

  • lifestyle factors (work schedule, family)

  • eating habits (morning or night person)

  • diet preferences (vegetarian, etc.)

  • objectives (improve metabolism, lose weight, healthier lifestyle, etc.)

Best Diet for Optimal Metabolism During Intermittent Fasting

The best diet to follow during intermittent fasting is one with whole, nutrient-rich foods. It should include:

  • lean proteins,

  • fruits and vegetables,

  • healthy fats,

  • and whole grains.

Whether you eat one or 5 meals during your eating window, consuming well-balanced meals will ensure sufficient energy levels to foster optimum metabolic function. 

Support Your Body’s Metabolism During Fasting

Give your body a hand during fasting by: 

  • Exercising: Boost your metabolism with exercise. Working out stimulates the burning of calories, increases energy use, and promotes muscle growth. 

  • Sleeping well: Insufficient sleep interferes with the body’s ability to process insulin, leading to improper processing of fats, where it is instead stored, and ends up as weight gain.

  • Proper hydration: Water is paramount for enzymatic reactions involved in energy production and nutrient metabolism. Moreover, water aids fat oxidation, and facilitates the movement of nutrients and waste.

Learn how Fastic can help you reach peak metabolism during your fast through its fasting tools, tailored fasting plans, and professional advice.

Disclaimer: It is advised to speak with a health professional before beginning intermittent fasting or a diet program. There may be side effects for people with certain medical conditions.

With Fastic, millions of people have achieved their desired weight, overcome disease and regained their quality of life.

Take the Quiz