The MYTH of Slow Metabolism, Starvation Mode (+ Intermittent Fasting)

(This post is also a podcast episode! Listen here.)

I know I promised to talk about sugar cravings and gut bugs at the end of the last episode, and I assure you I still will, but today’s topic comes up so frequently among our members that I wanted to cover it before we move on to bugs.

If you’re a member of Meal Mentor, make sure you download the weight-loss guide from the member library for more information.

Welcome to your metabolism.

If you’ve had difficulty losing weight, chances are you think you have a “slow metabolism” or you somehow broke your metabolism from past dieting.

Neither is true.

Before I jump into all the science and research that backs me up here (I can feel your skepticism) let me first explain what metabolism actually is.

Metabolism is the process by which your body converts the food you eat (or drink) into energy. Even when you’re asleep, your body needs energy for basic life functions like breathing and circulating blood. The number of calories (how much energy) used for these basic functions is known as your basal metabolic rate (BMR). Think of your BMR as the number of calories (energy) you’d burn laying in bed all day.

Your BMR is determined by your body size and composition (meaning the percentages of fat, bone, water and muscle), as well as your sex and age, which brings up another false belief: that your metabolism slows as you age. This is half true, but also half false!

As you get older, your muscle mass usually decreases, which consequently slows down the rate at which you burn calories. It’s not the passing of time and getting older that slows your BMR, it’s the change in your muscle mass.

Interestingly, my muscle mass has been totally unchanged for the last two years, but I because I have decreased my body fat, my BMR has changed.

I’ll give you the exact numbers here so you can get a good picture of this.

Sidebar: I used InBody body composition testing to get these numbers, which is the gold standard for determining true body fat and BMI. These machines use Direct Segmental Bioelectrical Impedance Analysis (BIA) which is a fancy way of saying they send electrodes through the body. It’s totally painless but incredibly accurate while calipers and water tanks are not.

Here are my numbers and I’ll post the scanned reports on for your viewing pleasure.

In December 2013 I weighed 133 total pounds. 32 of those pounds were fat. The rest was lean body mass meaning water and muscle. My body fat percentage was 23%, My BMI was 20, and my BMR was 1360.

I should note quickly that I had already been strictly using the meal mentor meal plans for a year at that point and it was the lowest maintainable weight I’d ever been at in my adult life.

I had another professional set of tests done last month (March 2016), three years after using the meal plans.

My lean mass is literally identical. I have the exact same muscle mass and water as I did in 2013, but I decreased my body fat from 32lbs to 18lbs. I literally only lost fat. 14lbs to be exact, almost half.

My body fat percentage is now 15% (down from 23%) my BMI is 18.4 (down from 21) and my BMR is now 1343 instead of 1360.

First, big thanks to the meal plans and meal mentor. That is incredible. 15% body fat is a real testament that abs are made in the kitchen!

Second, my BMR went down only 17 calories, a reflection of the fat loss and not muscle loss. I’m 5’7” so 1343 is a sobering reminder how efficient our bodies are and how little food we really need even if we are muscular and active. My 6-foot husbands was 1629 and a friend who is about 5’2” came in at 1150.

These numbers inadvertently bring me to another myth.

While men tend to have a higher metabolism than women, it’s not purely because they are male, but because men tend to have less body fat and more muscle mass. They also tend to be taller and bigger overall.

If a man has a higher BMR than a woman of the same age, height, and weight, it is only because he has more muscle than she does.

This next part is simple, though hard to accept about ourselves and what it means for weight-loss: The more you weigh, the more calories you burn, even at rest.

We can all agree an idling mac truck is using more gas than an idling mini cooper.

I can hear it clicking together for you now… but in case it isn’t:

People who weigh more tend to have a faster metabolism (not a slower one).

And as much as we don’t want to believe this, obese and overweight people tend to have a greater energy expenditure than people who are not obese or overweight.

Skinny people do not have a higher metabolism and that whole “high metabolism” thing is a totally false myth too.

While there are some individual variances in metabolism, those who seem naturally blessed with thinness despite their dietary choices aren’t gifted with superpower metabolism.

These people either have a higher total energy expenditure per day due to increased Non Exercise Activity Thermogenesis (NEAT for short) — little movements like twitching, fidgeting, or tapping throughout the day OR they restrict their eating to some degree.

Meaning, they sometimes eat smaller portions or choose healthy foods even though they’d prefer something else. Truth is we don’t see them at every meal. We’re only seeing them at the party or the restaurant and assume that is how they always eat. We underestimate how much they might restrict themselves at other times.

For example, I had a coworker who was very thin. Everyday she went out to lunch and brought back McDonalds, Burger King, Chick-Fil-A, and so on.

It was a mystery how she ate that and stayed so slender.

It wasn’t until I stayed with her for a few days that I got the entire picture. I realized she almost never ate breakfast and if she did, it was a few almonds. Her dinner was a bowl of cereal or a protein shake.

Her diet wasn’t the healthiest, but she wasn’t going over her calories, hence her thinness.

Quick sidebar: new research suggests some people absorb calories more easily than others, so that can be another explanation.

For now, let’s take a breath to recap what we’ve learned so far: There is no such thing as a “slow metabolism” save for exceedingly rare medical conditions that temporarily cause a slow metabolism, but this can be tested for and treated.

You also can’t blame your age or your sex. You can’t really blame your metabolism at all, as it turns out because the one and only beautifully simple thing about weight-loss is what? That’s right, there has to be a caloric deficit.

Thus, even if it is a little bit slower than it was 20 years ago, it’s still not “slow,” or broken, or the reason you’re not losing weight.

If you’re like me you’re thinking, okay I don’t have a slow metabolism, but I probably have a slowER metabolism, what can I do about that?

This is the fun part where I get to disprove “starvation mode” AND turn the worst advice you’ve even been given about metabolism on it’s head.

Raise your hand if you’ve been told that in order to lose weight, you need to eat 6 small meals a day.

That’s wrong. And it’ll actually make you gain weight, probably. More on that in a second.

“Starvation mode” doesn’t exist and intuitively you get that. You might not want to accept it, but the idea that if you don’t eat enough food you won’t lose weight is... hilarious.

But this wouldn’t be a science-backed research podcast if there wasn’t a giant, steamy caveat in every episode, so here’s today’s: Your metabolism will only slow down if you’ve consumed less than 50% of your required calorie intake for several weeks or months AND even then only by 10% AT THE MOST.

So you’re still going to lose weight even if you reached that point.

To be clear, I’m not encouraging you to do that, I’m just making a point to show you that even if you did “screw up” or “slow” your metabolism, it does not matter. You’ll still lose and lose steadily if there is any deficit. PLUS, numerous other studies confirm that once your weight has stabilized, your metabolism goes back up to expected levels.

No deficit = no loss. Broken record on repeat.

Here’s the super fascinating part: New research is showing that fasting, meaning not eating, can encourage the body to burn more fat and not muscle.

And there goes another myth! That weight-loss or dieting or not exercising means you’re losing muscle instead of fat. Not true, but I’m getting ahead of myself and I’ll get more into this later when I talk about Intermittent Fasting.

Let’s back up for a second and finish debunking “starvation mode.”

Research shows there’s no point at which your body stops burning fat, even during prolonged low-calorie diets or fasting.

As long as a caloric deficit exists, you will lose weight no matter if that deficit is small, moderate, or extra-large.

This is why people suffering from eating disorders such as anorexia, or POWs held captive with little to no food, will continue to lose weight, even once they are already underweight.

Shows like Survivor and Naked and Afraid are other good, real world testaments that “starvation mode” is a myth. If “starvation mode” existed, they would not thin out before our eyes. They would look and weigh the same on Day 22 as Day 1.

To be clear, I’m not encouraging or recommending an extremely low calorie “survivor” diet as they are nutritionally inadequate, I’m simply making a point.

Back to the big question: Is there anything you can do to speed up your metabolism?

Unfortunately there is little you can do to change, “jump-start” or speed up your BMR since it’s driven by the demands of your vital organs.

I know, wah. Wah. wah.

This is one reason why that “eat frequently” or “eat 6 small meals” is such crap advice. You can’t “stroke the metabolic flames” AND eating with such constant frequency has a massive downside when it comes to fat burning and weight-loss.

Which brings me to the real question we all should have been asking from the beginning.

The question isn’t “what can I do to speed up my metabolism?” But “what can I do to make my body burn more fat?”

Enter intermittent Fasting.

The premise behind IF is that by fasting you’re finally creating a situation where the body can burn fat as fuel without breaking down your muscles.

It’s all incredibly complex but here’s the best example I’ve come up with. Let’s say you stack up on canned chickpeas because it’s 10 for $10 this week.

There you are, with your 10 cans of chickpeas in your pantry, waiting for the great chickpea shortage of 2016 or the zombie apocalypse to come.

Now let’s say you’re out of all other food so you eat a can of chickpeas. Great! That’s exactly what those chickpeas were there for… But then, an hour later, you go out and buy another can of chickpeas to replace that can.

So your inventory never actually has the chance to go down.

That’s what happens with your body when you eat all day. You fat is the can of chickpeas. You have all this stored up energy for a rainy day but it never ever rains. You never go without food. Your body never has a chance to clear out the pantry.

There are a number of different strategies and I’ll post a link to the methods on, but the one most people have success with, which is the one I tried, is the 8-hour window approach. Meaning, you’re eating during a consecutive 8-hour window every day, fasting the other 16-hours.

Here are my thoughts:

Experimenting with intermittent fasting helped me find a better relationship and awareness with my true hunger.

It helped me see that I don’t need to eat all the time, or all day, and that if I’m hungry, it’s not an emergency.

Other MM members that have tried IF have said fasting taught them that hunger is like a wave, which ebbs and flows, but never gets bigger. They now know they can ride the wave if they have to and not eat out of fear of it getting bigger and “out of control.”

Intermittent fasting also forced us out of the habit of eating just because it was a certain time, rather than eating strictly because we were hungry. IF also broke our habits of fussing constantly about when I was going to eat and worrying about if I need to eat before I do this or that.

Fasting basically stops clockwork-systematized eating while simultaneously creating boundaries which did wonders for my “I’m bored” snacking habit. (It also made me realize I basically conditioned myself to feel hungry at certain times.)

If you think about it — it’s only in our recent history that humans have had such glorious access to an abundance of food. Our three meals a day habit is exclusive to the developed world, too. This is not the norm in underdeveloped nations.

Perhaps what surprised me the most about my experiment with IF was the noticeable increase in clarity and productivity, especially in the mornings. I expected to feel foggy or have low energy having not eaten, but I was more alert.

I also used to suffer from horrible bouts of “hanger” — feeling angry from hunger. I would frequently wake up in the morning or middle of the night ravenous. I also had days where my stomach seemed like a bottomless pit. I was insatiable. All of that went away when I began IF consistently. There is an adjustment period and a few people have said when they go off their schedule, the insatiable hunger and hangriness comes back.

My best explanation is that eating all day long created a lot of shifts and ranges in my blood sugar, which led to those unpleasant feelings. By eating larger meals less frequently, I stayed more level.

The New York Times also ran an article on the benefits of having a shorter eating window (proposing a 12-hour period) citing ample new research that eating less frequently can help cure and prevent obesity. I’ll include a link with the show notes on

This approach isn’t for everyone and does make your social life a bit challenging sometimes, but if you’re having trouble losing weight, you’re stuck at the last 10-15 pounds, you think hunger is an emergency, or you want to experience greater clarity and productivity, and you don’t have a medical condition or eating disorder that might be affected by this, IF could be a good experiment for you.

Lastly, since I’m sure you’re all wondering, what does IF look like with the meal plans? I tend to have my breakfast at 11, my lunch at 1 and my dinner at 6. My husband basically merges his breakfast and lunch into one gigantic meal. You’ll find your stride.

My husband says the reason IF works so well is because your head isn’t in the trough as many hours of the day, which is a fair point. Closing the window of opportunity to take in calories does make it easier not to overeat and create that deficit.

Download your free research-based 7-day meal plan at and leave the guesswork and science to me.

For next week's post I’ll be back talking about gut bugs and sugar cravings. To get notified when we post it join our email list.