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Home arrow Nutrition arrow Intermittent Fasting arrow Does Intermittent Fasting Slow Metabolism?

Does Intermittent Fasting Slow Metabolism?

Written by Edibel Quintero, RD
Fact checked by Rosmy Barrios, MD
Last update: October 15, 2023
3 min read 1517 Views 0 Comments
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does intermittent fasting slow metabolism

Intermittent fasting is the game changer when it comes to losing body fat. 

Positive results from intermittent fasting plans are reported worldwide. The scheduled eating plan can blast fat stores, improve brain function, and lower heart disease risk.

The assumption is that intermittent fasting speeds up the metabolism, based on the fast weight loss results that dieters see. However, sometimes the research suggests conflicting views. 

A slower metabolism means a person burns fewer calories when exercising and resting, making losing weight more difficult. 

A fast metabolism is the opposite. It means you burn more calories when exercising and resting, allowing individuals to consume more calories without gaining weight. 

You want a fast metabolism to help you lose weight in an ideal world. But can intermittent fasting slow your metabolism down? 

Keep reading as we dive into intermittent fasting and metabolism.

Does Fasting Slow Metabolism?

When you don’t eat enough calories, your metabolism can switch to slow mode.

This can make it more difficult to lose weight and more challenging to maintain your current body weight.

While eating fewer calories is a step in the right direction toward weight loss, consuming too few calories can backfire, causing metabolism to drop.

However, intermittent fasting doesn’t necessarily mean a severe calorie restriction. The limited eating window makes it easier to eat fewer calories, contributing to your weight loss efforts.

But with short periods of fasting and adequate calorie consumption, you shouldn’t cause your metabolism to slow down too much.

So, controlled fasting over short periods can potentially boost your metabolism, while with more extended fasting periods, metabolism slows as your body goes into starvation mode.

In starvation mode, you struggle to burn calories as your body holds onto fat.

Frequent calorie restriction diets are more likely to put the brakes on your metabolism than practicing intermittent fasting regimes sensibly.

Intermittent Fasting and Metabolism 

Your basal metabolic rate (BMR) refers to the number of calories you need to burn for your body to function properly. 

Intermittent fasting requires extended periods where you don’t eat. 

Long periods of starvation can indeed cause a significant drop in metabolism. But recent studies suggest that short fasting periods can boost metabolism.

Intermittent fasting for long hours can cause a metabolic shift where your body begins burning fat for fuel. Many people use intermittent fasting alongside the keto diet to reach the metabolic state of ketosis – a process that kickstarts your body’s ability to burn fat.

Effects of Fasting on Metabolism

Intermittent fasting affects metabolic processes significantly. 

Ordinarily, your metabolism uses regular carbohydrate consumption to fuel the body. When you fast, your body no longer has access to carbs and soon runs out of stored glucose. Your metabolism adapts to derive fuel from other non-carb sources instead. You begin to burn fat for energy, resulting in fat loss. 

As your body locates alternative energy sources, the levels of specific metabolites increase in the blood. 

So, to change the metabolic processes, you need to practice food abstinence and only consume calories during your eating window. 

While straightforward in theory, fasting can be hard to accomplish, especially if it’s your first time. 

Does Fasting Ruin Your Metabolism? 

No, fasting shouldn’t ruin your metabolism.

Further scientific research is required to fully understand the impact of intermittent fasting on metabolic health, but most of the evidence suggests that IF can improve metabolism.

If calorie restriction is kept to short periods with regular returns to normal calorie intake from a healthy diet, your metabolism stays on track.

How to Keep Metabolism High While Fasting?

To boost your metabolism during an intermittent fasting weight loss program, ramping up your physical activity can help.

Regular exercise will help speed up fat burning and support lean muscle mass, which supports calorie burning.

Any physical activity will increase your resting metabolic rate. Include a mix of strength training and cardiovascular exercise for best results.

You can also improve your metabolism by being conscious of your food intake during eating periods. Make sure you eat plenty of protein, drink plenty of water, and maintain an overall healthy lifestyle to support a healthy metabolism.  

A Word From Our RD

You may have heard in health news that skipping breakfast leads to a slower metabolism.

While drastically reducing your total calorie intake can cause the metabolism to slow, short-term fasts are thought to have some metabolic benefits.

Intermittent fasting may support several health benefits, from managing blood pressure and blood sugar to mitigating the risk of cardiovascular disease.

But as with both modern and traditional dieting, there is always the potential for adverse effects.

Intermittent fasting may result in nutritional deficiencies, muscle loss, eating disorders, and in some cases, weight gain from overeating when the fasting period ends.

Always seek medical supervision from your primary care doctor before trying any new routine, from intermittent fasting to calorie-restricted diets.

The Bottom Line

Does intermittent fasting slow metabolism? 

Without the sufficient calories that your body needs to function, you risk sabotaging your metabolism. But with metabolism fasting in short periods combined with regular calorie intake, your resting metabolism shouldn’t slow down.

Keep things in check by consuming enough calories when it’s time to eat, choosing a healthy meal over junk food, and staying hydrated with lots of water.

Written by Edibel Quintero, RD
Edibel Quintero is a medical doctor who graduated in 2013 from the University of Zulia and has been working in her profession since then. She specializes in obesity and nutrition, physical rehabilitation, sports massage and post-operative rehabilitation. Edibel’s goal is to help people live healthier lives by educating them about food, exercise, mental wellness and other lifestyle choices that can improve their quality of life.
The article was fact checked by Rosmy Barrios, MD
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