Watching calorie intake is for many the answer to losing weight, but there is concern about whether intermittent fasting slow down metabolism. I look at what the evidence says.
“You shouldn't eat less than 1200 calories a day.”
“Eating low-calorie food will slow down metabolism.”
We usually get this device from our close ones, including nutritionists and dieticians.
Still, intermittent fasting, also known as short-term fasting, where the calorie count is reduced to 500 calories, is becoming increasingly famous.
New research says that intermittent fasting boosts metabolism.
So, what's true about metabolism and fasting?
Does intermittent fasting slow down metabolism?
Let’s dive into the details.
What Is Intermittent Fasting?
Intermittent fasting is a new type of dietary invention.
During fasting, the person can't eat anything, and the word “intermittent” means that the fasting time comes and goes.
It can include time-restricted feeding, alternate-day fasting, modified fasting, and whole-day fasting.
What is the success rate of intermittent fasting?
Research has shown that people who eat only during a particular time window lose an average of 3% of their body weight, no matter when they eat.
And alternate day fasting led to a body weight loss of 3% to 8% over 3 to 8 weeks, with better results at 12 weeks. (Source)
Types Of Intermittent Fasting
AlternateDay Fasting
Alternate-day fasting means that the fasting and feeding days will alternate each day.
The person can freely eat anything on the feeding day and the calorie taken on the fasting day is 25%.
Time-Restricted Fasting
Time-restricted fasting involves the person should fast for a particular time every day, and then they can eat whatever they want the rest of the time.
Eating and fasting times can be allocated according to living habits or personal preferences.
Standard time allocation methods are: 16/8, 18/6, and 20/4.
16-hour fasting and 8 hours of eating, and the same pattern is followed for the other time frames.
Time-restricted fasting is more like Ramadan fasting, a unique form of fasting.
In this type of fasting, people cannot eat, drink or smoke during the daytime, but they are allowed to eat or drink from sunset to dawn.
Modified Fasting
The modified fasting method involves prescribed fasting days every week.
It involves plans like:
- 4:3 (3 days of limited calorie consumption)
- 5:2 (2 days of limited calorie consumption)
The calorie intake on the specified day is almost 1672~2508 kJ, and the person can freely eat during the rest of the week.
Compared to the continuous caloric restriction and Mediterranean diet, intermittent fasting doesn't limit calorie intake during the ad libitum period, so it has better tolerance and compliance. (Source)
Does Intermittent Fasting Slow Down Metabolism?
Intermittent fasting is typically linked with weight loss.
Still, reports say many people gain weight because of over-eating during non-fasting.
Also, any longer period of fasting can lead to a slow metabolism.
So, if you are concerned about the answer to “does fasting slow metabolism?”
Then the answer is “it can.”
Here, metabolism is crucial for understanding the connection between metabolism and intermittent fasting.
Metabolism is a chain of chemical reactions executed by the cells to transform food into energy.
The nutrient breakdown in the body can also be considered the calorie-burning procedure.
When you give your body many more calories than it needs, this energy will be stored in your body as fats.
The term Basal Metabolic Rate (BMR) calculates the amount of calories a person's body burns at rest.
Thus, people with low BMR burn fewer calories, and those with high BMR burn more after eating the same food.
People often consider the lack of food in the body as fasting, and lack of food in the body decreases the body's metabolic rate.
If you don't provide your body with sufficient food for long durations, it will slow down the metabolic rate and operate at a lower energy level.
Yet, once the everyday foods are consumed, this metabolic rate will stay the same, and you will start gaining weight.
So if we associate fasting with starvation or consuming 15 to 50% of calories much less than the body needs, the metabolic rate slows down. (Source)
Related: Can Intermittent Fasting Make You Tired?
Intermittent Fasting And Metabolism
Intermittent fasting centers across alternating between short periods of regular food intake and short periods of fasting.
Fasting is linked to a particular period where a small quantity to no food is consumed.
Intermittent fasting has been done for thousands of years, but “intermittent fasting” is a new form.
Surprisingly, studies suggest intermittent fasting is just as bad for your metabolism or even less so than traditional dieting.
People believe intermittent fasting boosts their metabolism because of fat-burning and lean body mass loss.
But studies recommend that a low percentage of lean body mass is burnt when losing weight with intermittent fasting.
Having more lean body mass indicates that the body's calorie-burning process is slow.
At the same time, short periods of fasting make the body fit into its fat stores and burn the fat mass for energy. (Source)
Does Fasting Boost Metabolism?
Fasting reduces the body's metabolic rate.
But if we talk about intermittent fasting, it's a bit different.
In IF (intermittent fasting), an individual eats healthy and nutritious food and follows a fasting and eating pattern.
So you won't starve, and it will not activate the starvation mode and defense response.
Intermittent fasting either boosts the metabolic rate or maintains its stability.
One research on 11 healthy men revealed that a 3-day fast boosted their metabolism by an incredible 14%.
This increase is considered to have happened because of the rise in the hormone norepinephrine, which boosts fat burning.
Still, more research is being done to evaluate how intermittent fasting may affect our metabolism. (Source)
What Are The Different Stages Of Weight Loss In Intermittent Fasting?
Intermittent fasting features the following 4 stages of weight loss:
- Fed state – this happens within a few hours after the food intake as your body starts absorbing nutrients and digesting food. During this state, the blood sugar level goes high, and a higher amount of insulin is secreted into the bloodstream. The levels of hormones like leptin and ghrelin also change.
- Early fasting state – after a few hours of eating, your body shifts into the early fasting state, which happens when amino acids, glycogen, and fatty acids are transformed into energy.
- Fasting state – this remains from 18 hours to 2 days of fasting. During this state, your body enters into ketosis (a state in which the body breaks down fats and uses them as an energy source.)
- Starvation state – (long-term fasting state) is the starvation state or long-form fasting state. It happens around 48 hours into fasting. During this time, the levels of insulin drop, the levels of ketone rise, and the breakdown of protein slow down to protect the muscle tissues.
What Mistakes In Intermittent Fasting Should You Avoid?
These are the top 7 intermittent fasting mistakes that beginners usually make in their weight loss journey with intermittent fasting:
- Choosing the wrong fasting plan.
- Ignoring your lifestyle (your schedule, your dietary restrictions, and the number of meals you eat a day)
- Not eating enough when you break the fast. It can badly affect your health.
- Overeating when you break the fast.
- Choosing the wrong foods during the eating window.
- Not staying hydrated. It can cause nausea, fatigue, dizziness, headache, and constipation.
- Giving up when you don’t notice immediate results.
If you avoid these mistakes and do intermittent fasting correctly, you can efficiently and safely lose weight.
Does Intermittent Fasting Slow Down Metabolism: Closing Thoughts
If you do intermittent fasting the right way, you will either improve your metabolism rate or see no change in it.
However, following a proper meal plan for intermittent fasting can help you get results faster without hurting your metabolism.
Proper intermittent fasting plans also include the intake of essential supplements to provide your body with all the necessary nutrients to perform the daily chores.
Lastly, intermittent fasting can be highly effective for those who want to lose unwanted pounds and shed extra body fat.