IF WITHOUT KETO

Will Intermittent Fasting Slow Your Metabolism? [The Truth]

Intermittent fasting (or time-restricted feeding, as referred to by science), has become more prevalent in this past decade. For those following a ketogenic diet, it's almost inevitable that you'll eventually hear of and/or try intermittent fasting to optimize your results.

But one can only wonder what prolonged periods without food regularly might do to their metabolism.

Will intermittent fasting slow metabolism? According to the current scientific literature, intermittent fasting does not have any measurable effect on the metabolism, which includes resting energy expenditure and thyroid-stimulating hormone. 1

In this article, I'm going to cover what exactly goes into total daily energy expenditure (how many calories you burn daily), some of the current literature on IF, metabolism while EXTENDED fasting, things you can do to keep metabolism humming, and much more.

Does Intermittent Fasting Slow Metabolism?

A common concern among people who want to try or already implementing intermittent fasting (IF) is whether or not it will slow down their metabolism, aka starvation mode.

After all, that would be counterproductive to your weight loss goals, so I get it.

Over the decades we've come across so many myths and misconceptions, to name a few:

Eat breakfast to “boost your metabolism.”
Eating small meals every 2-3 hours keeps your “metabolism burning.”
Don't eat after a specific time, because it will lead to fat.

I had these very same questions, which led me to go down the rabbit hole of intermittent fasting.

First, let me start by saying that starvation mode DOES NOT exist, nor can you permanently damage your metabolism, which I'll get to shortly.

While there are specific processes in your body that do begin to slow down (downregulate), it's not WHAT and WHY you may think.

How To Calculate Total Daily Energy Expenditure

So here's the deal, long story short, to effectively lose weight you must burn more calories than you consume.

Despite what some guru has led you to believe.

If you didn't believe that, you wouldn't need to worry about a slow metabolism, but you're here.

How many calories we burn throughout the day is what's referred to as your total daily energy expenditure (TDEE). Your TDEE consists of four main components:

Resting Metabolic Rate (RMR)
Thermic Effect of Food (TEF)
Physical Activity (PA)
Non-Exercise Activity Thermogenesis (NEAT)

What Is Resting Metabolic Rate (RMR)?

Your resting metabolic rate (RMR) is the number of calories (energy) you burn to maintain essential bodily functions, such as breathing, keeping your heart beating, and maintaining your body heat.

RMR is by far the most significant component of total daily energy expenditure 2 unless you happen to be a professional Ironman triathlete or Tour de France cyclist.

To summarize RMR, it's the number of calories you burn if you were to do absolutely nothing all day except sleep or lay in bed and not move.

RMR may be what most people consider to be their “metabolism.”

What Is The Thermic Effect Of Food?

The thermic effect of food (TEF) is the amount of energy (calories) required to eat, digest, absorb, and store food.

According to research, TEF accounts for nearly ~10% of our total daily energy expenditure (TDEE). 3

You can look at TEF as the number of calories it takes to digest the food you eat. Certain macronutrients, more specifically protein, require more energy to digest than carbohydrates or fat.

So one can argue that eating a more significant proportion of calories coming from protein would be an easy tool to increase this segment of your TDEE.

What Is Physical Activity?

Physical activity (PA) is the most self-explanatory of the four pieces of your TDEE.

Physical activity is any voluntary exercise you engage in. Lifting weights, going for a run, or playing a sport all fall under physical activity?

What Is Non-Exercise Activity Thermogenesis (NEAT)?

NEAT is all the activity you engage in daily that ISN'T physical exercise. NEAT includes activities like walking, tapping your feet when you sit, doing laundry, and even sex (that is unless you purposely engage in it for exercise).

Research shows that NEAT may vary by up to ~2,000 calories per day in individuals that are of the same height and weight. 4

To put that into perspective, a pound of fat has ~3,500 calories, so a little more than a pound of fat over two days.

This may explain the reason why you see someone who starts at the same height and/or weight as you lose weight slower or more rapidly than yourself.

They simply move around more throughout the day.

NEAT INTERMITTENT FASTING AND METABOLISM

NEAT also plays a significant factor in why you may believe that your metabolism is slowing down. Naturally, as you diet, your body decreases its spontaneous activity, thus reducing its average daily energy expenditure. 5

Research also shows that this adaptation to reduced NEAT can sometimes continue, even after we've stopped dieting, thus resulting in weight regain after you've returned to regular eating. 6

NEAT may ultimately be the culprit when one feels their metabolism has “slowed down” or their body is in “starvation mode.”

A good counterbalance may be to use a step tracker or other smart device to ensure a minimum daily movement or step count.

Intermittent Fasting Metabolism Study

There have been numerous studies on Intermittent Fasting (IF) or Time-Restricted Eating (TRE), as cited by the scientific literature, in both sedentary and athletic populations.

In the context of weight and fat loss, IF's primary mechanism of action is its ability to control calorie intake. Meaning, by restricting your eating window, people seem to eat less food overall naturally.

In one study, participants were told to delay their normal breakfast time by 1.5 hours and move their normal dinner times up by 1.5 hours. This simple shift in eating times, and with no other instructions, resulted in less food eaten, and thus weight loss. 7

Another study had individuals eat within a 10-12 hour eating window of their choosing.

Again, no other instructions were given (they could eat whatever and whenever they wanted as long as it was in a 10-12 hour window). 8

Can you guess what happened? Subjects spontaneously ate less, and thus lost weight.

Just to reiterate, these subjects were also not following a ketogenic diet.

Wondering if you can do IF without keto?

In terms of metabolism, this study following individuals using a 16/8 feeding window found a slight reduction in T3, but no changes in thyroid-stimulating hormone (TSH) or resting energy expenditure.

It would seem as though no studies can show any meaningful impact when it comes to slowing the metabolism.

Does Extended Fasting Slow Metabolism?

Most people who do intermittent fasting (IF) usually engage in a 16/8 fast to feast eating protocol. However, some specific individuals like to take things a little further and do much-extended fasts.

We're talking about 24, 48, 72, and longer fasts.

But do extended fasts slow metabolism? Extended fasts do not seem to slow metabolism, but quite the opposite. Resting energy expenditure increases during the early stages of extended fasting. 9

You read that correctly.

Extended fasting, at least during the first 72 – 84 hours, research has shown an INCREASE in metabolism and plasma norepinephrine.

Norepinephrine plays a central role in the regulation of energy metabolism, which may explain the increase we see during short periods of starvation.

This might be a way of the body, kicking us into high-gear to find food. Our ancestral biology is telling us to go and hunt some food before we die of starvation.

What Are The Drawbacks Of Intermittent Fasting

Now that we've established intermittent fasting, even extended fasting, doesn't seem to slow down the metabolism, what are the potential downsides of IF?

Decreased Muscle Protein Synthesis (MPS)

If muscle gain is of any concern, intermittent fasting may not be the most “optimal” protocol. Notice the word optimal; I didn't say you couldn't gain muscle.

While you can gain muscle by eating all your meals in a small eating window, you won't be doing your body justice in terms of building muscle.

Muscle protein synthesis (MPS) is the process of building muscle mass.

Think of muscle protein synthesis as money going into your bank account, and muscle protein breakdown (MPB) as debits drawn from your bank account.

Building muscle requires more money (MPS) going into the account, then money drawn (MPB) from the account.

To effectively stimulate MPS to near maximal levels requires ~20 grams of protein, while going up to 40g may result in a ~10% increase.

Now, the problem with intermittent fasting is the limited amount of times we can stimulate this process. MPS, once stimulated, experiences a refractory period where the muscle can no longer respond to incoming amino acids, referred to as the muscle full effect. 10 11

During this period of ~ 3 hours, MPS can no longer be stimulated.

You can see how IF, and consuming only one or two meals would not be ideal for stimulating this process. In fact, it's entirely possible to lose muscle on keto if you're not careful.

Food focus

Some people decide to give intermittent fasting a try but like to eat small meals throughout the day.

You may have read that intermittent fasting is the holy grail for weight loss. Still, the reality is both IF and continuous energy restriction (smaller meals throughout the day) will generally provide the same results. 12

Given you keep the calories the same.

If IF stresses you out, causes you to continually watch the clock like a hawk waiting for your eating window, maybe it's time to try a different approach. I'd argue to say you're doing more harm than good as there is very little to no benefit when it comes to IF and weight loss.

However, if you enjoy condensing your eating window, enjoy larger meals less frequently, and eating in a time-restricted fashion allows you to adhere to your diet much better, then keep doing it.

May lead to binge eating

There were times that IF opened the door to overeating, at least for myself. I would go the whole day without eating, so by the time it was time to eat, I was RAVENOUS.

Intermittent fasting led to my appetite getting out of control… sometimes.

If this sounds like you, maybe IF isn't for you either.

This is the case for many people who utilize programs like Speed Keto which adopts the one meal a day (OMAD) schedule of eating.

How To Keep Metabolism High While Fasting

While some metabolism downregulation is expected due to weight loss, not so much intermittent fasting, there are things we have within our power to change.

There are a multitude of reasons why you may not be losing weight or hit a plateau. Want to find out more? Check out my article on the 11 Reasons Why You're Not Losing Weight On Keto.

NEAT

As mentioned earlier, a significant proportion of our daily calories that IS in your control comes from non-exercise activity thermogenesis (NEAT).

People of the same body weight and height can vary by as much as 2,000 calories per day, which is nothing to scoff at.

NEAT is one of the biggest culprits, if not THEE biggest culprit when it comes to hitting a stall or plateau in your weight loss efforts.

The best way to keep your metabolism high while fasting is simply to MOVE MORE!

I'm a big fan of keeping a daily step count, but if that causes anxiety for you, that may not be ideal for you.

This is the part where I say, every little thing adds up, and that's because it does.

The best way to increase your NEAT is by building in small habits a little at a time.

Park further when you go to the store or the office
Take the stairs instead of the elevator
Walk (when you can) instead of driving
Take your dog out for a walk
Do some chores you've been putting off
Pick up the hobby you've always wanted to

The simple act of staying active throughout the day will burn more calories than hopping on that treadmill for 20-30 minutes, and more enjoyable at that.

Pedometer intermittent fasting metabolism slowdown

Eat more protein

Another tip is to increase your protein intake.

You're almost always better eating TOO MUCH protein than not enough protein.

Not only is protein considered the most satiating macronutrient 13, it also burns the most calories through digestion (thermic effect of food).

Just to illustrate the different macronutrients and their effect on metabolic rate:

Protein ~15-30%
Carbohydrates ~5-10%
Fats 0-3%

And while you won't be consuming extremely high protein intakes, chronic consumption of a diet high protein has proven to be relatively safe with no harmful effects on any measure of health. 14

Of course, if you have a pre-existing disease or impaired kidney function, this would not be ideal.

How much protein should you eat? A good rule of thumb is to eat 1 gram per pound of desired body weight. Meaning, If you weight 200 pounds but wish to drop down to 180, then you would consume 180 grams of protein per day.

Ideally, you would eat 1 gram per pound of lean body mass per day (lean body mass is your total weight – your fat weight).

Include resistance training

Aside from the numerous health benefits resistance training provides, having more muscle equates to a faster metabolism.

During periods of calorie restriction (dieting for weight loss), weight from both fat AND muscle tissue is lost.

Our goal during periods of weight loss should be not only to lose weight, but ONLY lose fat.

This means we want to spare all of the muscle we currently have or possibly increase it.

If you've never lifted weights before, you're missing out on a prime opportunity to lose both fat AND gain muscle, known as body recomposition.

Beginners who undertake weight training have a high probability of accomplishing both tasks in the short term, but most end up shortchanging themselves by trying to diet without exercising.

Additionally, including any type of exercise is often one of the predictors, those who successfully manage to KEEP the weight off employ.

It's said that 6 out of every 7 people who are overweight are able to lose weight at some point during their lifetime. Up to ~95 of these people end up regaining the weight.

What's more alarming is that one to two-thirds of these same individuals end up heavier than when they started.

Intermittent Fasting For Weight Loss

The number one reason that intermittent fasting has been shown to aid in weight loss is by causing individuals to eat less over time.

There is no inherent benefit to intermittent fasting over spreading out your meals throughout the day unless it helps you maintain a caloric deficit.

What Supplements Help Increase Metabolism

Very few supplements on the market are worth taking, at least when it comes to fat loss.

Wondering if you can take fat burners on keto and/or IF? The answer is yes, but let's hold onto that thought for a moment.

Most supplements, especially ones claiming to burn fat, are useless.

The real mechanism most supplements work is to help lighten your wallet.

Just take a look at my shark tank keto diet pill review, which is scamming hundreds of thousands of people.

And that's the truth.

Want to know what the most effective supplements are?

In short, the only ones that are likely to be useful and worth considering are:

Caffeine
ECGC (Green Tea Extract)
Yohimbine HCL (If you're already lean)

You'll have to read the other articles if you're interested in more information about these specific compounds and how they may aid in fat loss.

If you're looking for fat burners specifically, then check out this article: Can I Take Fat Burners On Keto?

If you want to know more about any effective supplement in general, then check out this article: The Best Keto Supplements Of 2020.

The Takeaway

Research has shown that intermittent fasting does not have a detrimental effect on metabolism. In fact, short periods of extended fasting have shown that metabolism increases.

However, metabolism does downregulate slightly through other mechanisms during periods of weight loss.

First, you're carrying a lighter body, so you burn fewer calories doing the same activities.

Secondly, your spontaneous movements (NEAT) generally goes down.

Lastly, to combat these adaptations, it's suggested that you remain active throughout the day and engage in resistance training as muscle is more metabolically active than fat.

Intermittent Fasting Without Keto? [A Better Approach]

When people hear about or adopt a ketogenic diet, they begin to dig around for ways to optimize their results or speed things along. Eventually, I want to say the majority of people who follow a ketogenic diet learn about intermittent fasting.

Intermittent fasting or IF may be used without the use of a keto diet. Intermittent fasting is a schedule of when to eat versus a ketogenic diet, which is more of what to eat or not eat. The two may be used together or entirely separate from one another with great success.

However, for one reason or another, you may find yourself wanting to transition off of a ketogenic diet, but still wanting to implement the intermittent fasting (IF).

In this article, I'll go over if you can still lose weight without keto, different intermittent fasting protocols, why IF may not be all that it's cracked up to be, and possibly a better alternative to IF.

Can You Lose Weight Intermittent Fasting Without Keto?

I get asked this question quite often from individuals who found keto and IF but want to move to a diet with more moderate carbohydrates.

Can you lose weight intermittent fasting without keto?

And the answer is… of course, you can.

You can lose weight without keto AND without intermittent fasting. You may have had trouble losing weight previously, and keto and/or IF seemed like the holy grail, but it was just another means to an end.

As the saying goes, there's more than one way to skin a cat.

You can look at both keto and intermittent fasting as tools you can implement when the time is right, but don't confuse that with them being THEE only tools you can use for weight loss, weight maintenance, or even weight gain if that's what you're after.

How To Lose Weight Without Keto

You may have been led to believe that eating VERY low-carb or keto was the only way you'd be able to lose weight. I get it, I was in your shoes, and I too believed that at one point, but I assure you that's not the case.

While lowering carbohydrates or following a ketogenic diet may help many individuals, as it did me, and possibly you, it's not the be-all-end-all.

Keto can be great for many reasons:

While keto may be great at helping you lose weight, and some people find it a sustainable lifestyle, there are just as many who do not want to stay keto forever.

I get it.

As much as you've been led to believe that carbohydrates are evil and calories don't matter, neither one is true.

Weight loss still comes down to the fundamental principle of calories in vs. calories out. (CICO) The hard part about calories in vs. calories out is that those numbers are always changing, which makes it hard to calculate accurately.

ENERGY DEFICIT VS ENERGY BALANCE IF WITHOUT KETO — While energy in is easier to calculate, energy out is much more dynamic.

Plus, most people don't want to have to count calories.

And you don't have to.

So I Have To Count Calories To Lose Weight?

Counting calories IS NOT required to lose weight, and you definitely can lose weight without counting calories.

But don't confuse not having to count calories with being the same as calories don't count.

There may be a benefit for specific individuals to count calories, and the research also shows a trend towards more weight loss and maintenance of weight loss with those who do track calories, but that’s a whole other discussion in and of itself.34

Which leads me to my next point, the adage of eat less move more IS also true, but we can all agree it is not helpful advice.

The reason you may have lost weight on keto, with or without exercise, and possibly without counting calories, is because ketogenic diets are known for suppressing appetite5, which causes you to eat less overall.

No matter how you put it, every diet that causes weight loss works through the same fundamental principle, it causes you to eat less.

Therefore, the only way to lose weight is to eat in a manner that allows you to remain in a caloric deficit consistently.

Whether that's keto or not.

How Intermittent Fasting Helps You Lose Weight

First, let's define what intermittent fasting is.

Intermittent fasting is an umbrella term to describe various meal timing schedules that involve periods of fasting (not eating or reduced calorie intake) with periods of non-fasting (eating).

What most people refer to as intermittent fasting should really be referred to as time-restricted eating (TRE). Intermittent fasting can encompass periods of dieting (calorie restriction), regardless of daily timing, with periods of not dieting.

On the other hand, time-restricted eating (TRE) is restricting your eating window to a particular time or hours in the day.

Makes sense, right? Time-restricted eating means restricting the time that you eat.

Intermittent fasting means times of not eating (fasting) OR eating less (calorie restriction) with times of eating (not fasting) or not dieting (not calorie-restricted).

I'm assuming most people will be eating within an 8-hour eating window or less, which I will intermittently (see what I did there) refer to as both intermittent fasting (IF) and time-restricted eating (TRE).

So how does time-restricted eating help you lose weight?

For the most part, time-restricted eating helps people lose weight through the same fundamental I spoke of earlier. TRE causes weight loss by helping you achieve a caloric deficit.

Calories in vs. Calories out

Had you eaten the same amount of calories you did during your 8-hour eating window, but spread throughout the day, there would be no statistically meaningful difference in weight loss. 6

Since that cat is out of the bag, how does IF or TRE help you lose weight?

For one reason or another, condensing the eating window works for some people.

Certain individuals find it easier to eat bigger meals less frequently, while some people prefer smaller meals, but more frequent.

In one study, participants were only instructed to delay their breakfast time by 1.5 hours and eat dinner 1.5 hours earlier, thus shortening their eating window by 3 hours. No other rules were given about what to eat or how much to eat.

A simple change in the time frame of when these people ate was enough to cause them to consume significantly fewer calories and, as a result, lose weight. 7

In another intervention, participants ate within an 8-hour feeding window, but at whatever time of the day they preferred. Again, no other rules were given, and over 16 weeks, participants lost more than ~6.5 lbs. 8

Maybe you're not hungry in the morning, that's great, skip breakfast and have bigger meals later in the day.

However, if skipping breakfast causes you more stress because you're starving when you wake up, then eat when you wake up!

There is no inherent benefit for weight loss in terms of TRE unless that benefit is allowing you to adhere to your diet better and eat less overall, which is the main benefit for people.

Many individuals like to be social in the evening or have bigger dinners, and many people want to go to bed on a full stomach rather than semi-hungry. IF allows these individuals to stay under their calories for the day, with makes it applicable to them in losing weight.

As you may begin to notice, the main benefit of intermittent fasting on weight loss is the ability to cause people to eat less by restricting the eating window.

Therefore, my advice would be to eat in a way that you enjoy and that you can adhere to.

In the end, the most critical overlying factor will be the total amount of food (calories) you eat, not the times that you eat it.

What Is Better Than Intermittent Fasting

If intermittent fasting, aka time-restricted dieting, is no better than intermittent fasting, what do I recommend?

Everyone's different has different needs and can tolerate different modalities. Without knowing YOU as a person and your history/background, it's almost impossible for me to tell you what to do.

BUT, here's what I do recommend for most people.

Instead of intermittent fasting, or in addition to, if you enjoy that style of eating, I recommend intermittent dieting (or intermittent fasting as per the scientific definition).

That means, alternate periods of dieting and actively trying to lose weight with periods of non-dieting and maintaining your weight, aka taking a diet break.

Now, when I say diet break, this doesn't mean a free for all. You should be eating a little more food, just enough to maintain your weight plus or minus a pound.

This period of increased food acts to help to give you a break both psychologically, but physically as well.

A study, known as the MATADOR study, took two groups of people who dieted a total of 16 weeks. The first group of people dieting for 16 straight weeks, the second group of people also dieted for 16 weeks BUT completed the 16-weeks in 8 x 2-week blocks.

Meaning, the second group dieted for two weeks, followed by two weeks of maintaining weight (more food).

In the group that intermittently took breaks every two weeks, greater weight and fat loss was achieved. Additionally, the same group also had a higher success rate of maintaining weight loss after the intervention. 9

While a break every two weeks isn't necessary, it's essential to realize that now and then, we have to take a break both mentally and physically from dieting.

It would seem as though taking periodic breaks also allows us to tackle the next few weeks energized and refreshed, thus providing a better outcome.

Besides, it's much easier to stay the course when mentally you will know there's a break every few weeks versus every few months, or *gasp* not at all.

Whether it takes you a month or six months to lose the weight, will it matter when you look back five years from now? I bet it won't. You'll be glad that you lost the weight in the first place, and managed to keep the weight off through smart decisions and building up healthy habits.

Dieting is a stress, and we can't be continuously stressed without eventually breaking.

Here is a generalized guideline of how often to take a break while dieting.

So Can You IF Without Keto?

You can implement intermittent fasting with keto or ANY other diet you choose to follow.

However, keto may allow some people to adhere to an intermittent fasting protocol easier due to the appetite-suppressing effects of a ketogenic diet, so you would have to try for yourself.

Intermittent fasting or time-restricted eating is just a method of eating that is convenient for some individuals or allows them to adhere to a caloric deficit, regardless of foods eaten.

A caloric deficit is the overlying determining factor whether you lose weight or not despite what other keto gurus may lead you to believe.