Does Dieting Ruin Your Metabolism?

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Today’s Health Upgrade

Fact Or Fiction
Does Dieting Break Your Metabolism?

You do everything right for five weeks, and the scale won’t move. In those moments, it’s easy to blame your metabolism. Or wonder if something you did in the past has messed up your future.

Think of your body as a parked car that still burns gas. Lose weight, and you become a smaller car that needs less fuel. During a diet, your body may conserve a little more energy. The question is whether this extra slowdown lasts.

Metabolism does slow during weight loss, but a well-controlled study suggests most of that additional slowdown fades after you stop dieting. More importantly, it doesn’t appear to explain who regains weight.

A team of researchers put adults with obesity on a 1,000-calorie-per-day meal-replacement diet for eight weeks. The participants lost about 30 pounds, then increased their calories enough to maintain their new weight. Researchers compared each person’s resting metabolism with what someone of the same size would be expected to burn.

Among the 45 participants tracked for a full year, resting metabolism was 107 calories per day below predictions immediately after the diet. In other words, when weight drops, resting metabolism is supposed to decrease. But initially, the drop is bigger than expected.

However, four weeks later, the gap had fallen to just 49 calories. After a year, it was just 7 calories, which is basically no difference.

On average, participants had regained about nine pounds by then (roughly 30% of what they lost), even with monthly check-ins.

But the people whose metabolism slowed the most weren’t more likely to regain weight.

That doesn’t mean a “broken metabolism” is impossible. It can happen, but it’s more unlikely and regulates over time.

So what causes regain? The bigger force appears to be appetite.

In a year-long study of adults with type 2 diabetes, researchers estimated that for every 2.2 pounds lost, people ate about 100 more calories per day than before. That’s more than three times the drop in calories burned, which is why keeping weight off requires a plan for hunger (protein, fiber, sleep, and activity), not just a lower calorie target.

That doesn’t mean metabolic adaptation is imaginary. Some people experience a greater slowdown than others, which can extend the time it takes to reach a goal, and other studies have reported longer-lasting slowdowns. This study also measured only resting metabolism, so it doesn’t tell us what happened to calories burned through daily movement.

Still, the average additional slowdown was relatively small (roughly the calories in a tablespoon of peanut butter), and most of it disappeared once the participants stopped actively dieting.

If progress stalls, start by updating your calorie target. A smaller body naturally burns less, so recalculate approximately every 10 pounds you lose.

Then log everything for one week, including cooking oil, drinks, and weekend bites. In one study, people who believed they couldn’t lose weight underreported their food intake by nearly half.

There’s also no evidence here that you need a special “metabolism repair.” Eating at maintenance cut the metabolic gap in half within four weeks, and it was gone by one year. And if the scale jumps a few pounds when the diet ends, remember that replenished carbohydrate stores hold water. That early increase isn’t necessarily body fat.

Your metabolism probably isn’t broken. But after weight loss, the plan that worked for your old body might need adjusting for the smaller one you have now.

If you don’t want to think about adjustments but want help keeping off the weight (or losing weight or building muscle), the Nutrition Tracker in the Pump Club app does the thinking for you. Set your goals and use Arnold Intelligence to help you figure out what to eat to stay on track, without the stress or calorie counting.

Together With BEDGEAR
How Much Is Your Pillow Height Affecting Your Sleep?

A pillow seems like a comfort choice: soft or firm, foam or feather, cool side up. But for seven or eight hours, it sets your head and neck position and changes how much heat builds up around your head. And if you can’t seem to feel well rested, a good place to start is what you rest your head on every night. 

A pillow can change your neck position, how stiff you feel in the morning, and how much heat builds up around your head, all of which might influence the quality of your sleep. 

In one laboratory study, raising pillow height changed neck angle and curvature. But no single height worked best for everyone.

A 2021 review reached a similar conclusion: height and shape appear to matter more for neck position than what’s stuffed inside the pillow.

That can influence how your neck feels when you wake up. People who reported poor sleep were also more likely to wake with neck stiffness or pain around the shoulder blades, but that association can’t tell us which problem came first.

And that’s half the story. The other part is your pillow's role in keeping your head cool, because heat affects deep, restorative sleep.

Your body needs to release heat to fall asleep, and much of that heat loss happens through your hands and feet. But your head also releases heat. Unfortunately, most pillows don't handle moisture in a way that supports sleep.

Your head and neck sit pressed against one small surface for hours, so heat and moisture build up there and have nowhere to escape unless you use the right materials.

In a small study of people who had trouble falling asleep, a pillow cooled to 16°C helped them fall asleep faster than one set at 26°C. And in a hot, humid sleep lab, a cooling pillow kept nighttime waking closer to what researchers observed in a comfortable room.

If you regularly wake up with a stiff or sore neck, it's worth testing your pillow. Side sleepers generally need more height than back sleepers, but the right fit is individual. 

That’s how we discovered BEDGEAR. 

Most pillows come in one height and get sorted by feel: soft, medium, firm. That tells you how it feels when you press it. It tells you nothing about where your neck ends up at 3 a.m.

BEDGEAR sizes its pillows by height, from 0.0 to 3.0, matched to your body and how you sleep. A broad-shouldered side sleeper has a lot more space to fill between ear and mattress than a smaller back sleeper, so they get a taller pillow. It’s a simple idea. It’s also rare.

Finding your size takes about two minutes. The free PillowID quiz asks seven questions about your sleep position, your build, and whether you run hot, then recommends a height and fill. Many of their pillows are dual-sided too, firmer on one side and softer on the other, so you can change the feel without changing the height.

When we tested pillows that keep you cool, the best option for improving sleep was the Night Ice pillow by BEDGEAR, and the science supports the testers' findings.

Where most cooling pillows stop at the surface, Night Ice goes deeper, with three layers of cooling technology working from cover to core. Its Ver-Tex™ cover feels instantly cool to the touch as advanced cooling yarns help draw heat away from your body. Inside, cooling fabric within the Active Core adds another layer of protection against heat buildup, while ventilated React™ foam paired with cooling gel delivers soothing, pressure-relieving comfort and adaptive support. 

Along the sides, breathable Air-X® mesh and built-in air vents provide directed heat release, allowing warm air to escape instead of getting trapped around your head. The result? A pillow engineered to keep you cool and comfortable all night long, not just when your head first hits it.

No pillow regulates your temperature. Your body does that. But a good pillow gets out of the way, letting heat and moisture go where they belong instead of piling up under your head all night.

Want to take advantage of our favorite pillow for better, science-based rest? APC readers get 20% off BEDGEAR pillows and bedding with code “PUMPCLUB20.”

You spend a third of your life with your head on your pillow. It’s worth making sure it’s the right fit. 

Adam’s Corner
Thank You, Mike

Last week, I shared the email that read like a one-star review of my personality.

Mike got his wish. Sort of.

I spent the week shooting videos with our Pump Club app team and some of our members. And because even writing “nonsense” still takes a lot of time and multiple drafts, I couldn’t share anything new last week.

So instead of a column, I shared a short note. I quoted Mike. Then I handed the keys to all of you with a line I meant literally: “So, this week, you get to play editor.”

I had no plans to end the column. A lot of you assumed I did. A few of you sounded relieved. And Ketchell joked (ok, maybe he was 20% serious) that I emailed 1.3 million people just to get a pat on the back.

As I told Ketch: the real reason was two-fold. First, I didn’t want to disappear without saying anything. And I genuinely thought it was a good opportunity to get more feedback about what you want. When you write every day and a column every week, more ideas are never a bad thing.

But something in all those responses made it clear that you misinterpreted my reaction to Mike.

Whether you agree or disagree with Mike, his email (and others like it) keeps me honest.

If you’re going to give us your time, I want to make sure we respect it.

But respecting and considering opinions doesn’t mean losing perspective, which happens all too often in disagreement.

I wrote Mike back the day he emailed us. I thanked him, and then I pointed out some math.

We send five newsletters a week. Each one typically has three or four items. My column is the last item, once a week, on Thursday. So if he doesn’t like it, the column might be the easiest thing to skip because it’s always on the same day, in the same location, and doesn’t block access to any additional information.

That’s the practical answer.

But from your responses, I took away something that can serve us all when feedback strikes a nerve.

Is It An Attack Or Feedback?

We love the responses we get daily, but this might be the most emails we’ve ever received on a single issue. So thank you, all of you, for taking the time.

Most of you were kind and protective. You told me that the column is some of your favorite work and the thing you share the most. It helps you reflect on life, prepare for what might be ahead, or even wish you’d reached some of those realizations earlier in life.

At the same time, many people agreed with Mike. And they let me hear about it.

You told me the column is too long. The column is selfish. Some said it makes me seem like I have everything figured out and that I’m “humble-bragging.”

I couldn’t respond to all the comments, but I tried to read as many as possible. There was a lot of good feedback that some could easily write it off as “hate mail.”

For the record, I don’t have it all figured out.

This column is me working out loud on something I have yet to solve, am still making sense of, or moments of insight I find valuable that I hope are relatable: death, parenting, insecurity, and the strange business of being a mid-40s guy who has spent 25-plus years helping people get healthier and still has to relearn half of it himself.

I understand why it lands differently than everything else in the newsletter. It is long. It reads more like a journal entry than a tip. It’s the world through one person’s eyes, and that’s a narrow window if it isn’t your view.

But I want to address your response to Mike’s blunt assessment.

You were worried about how the criticism would affect me. And that I shouldn’t take it personally. Or that I should ignore it completely and Mike should kick rocks.

Part of me appreciated the protective nature.

Part of me worried we’ve reached a point where every bit of criticism or disagreement feels like an attack, or that we don’t have the internal armor to absorb things that are a bit uncomfortable or offer ways to improve.

We need the Mikes of the world. And we shouldn’t always assume they are operating in bad faith, even if sometimes they are.

Rethink The Red Ink

I’ve mentioned this before, but early in my career, as a young editor at Men’s Health magazine, I’d turn in a draft I was proud of, and it would come back looking like a crime scene. Red in every margin. Whole paragraphs struck through. Question marks where my favorite sentences used to be.

The first few times, I read it as a verdict. Maybe I’m just not good at this.

Thankfully, my mentor, the great Ted Spiker, helped me see what those edits actually were. Someone spent time on my work because they thought it could be better.

The bloodbath edits weren’t a sign I sucked. They were the path to better.

As Arnold says, ignore the naysayers. But that doesn’t mean you ignore all criticism. Both can be true at once, and the whole skill is learning to tell them apart. Some feedback is noise. Some of it is coaching, and sometimes a stranger delivers it without bothering to be gentle.

Acknowledging the bad doesn’t mean you give in to it. It can be part of your roadmap.

You have your own version of this.

The one line in a performance review you keep replaying on the drive home.
The coach who watched your squat and said, flatly, that depth is not a suggestion.
The kid who informs you, with total sincerity, that you’re kind of grumpy in the mornings.

The reflex is to defend yourself or to fold. There’s a third option, and it’s the one good editors teach you: get curious about what’s true in it, what you can toss, and what you need to do to take what you need and become better.

Embrace The Pressure, Set The Standard

Writing this column, and more accurately the entire newsletter, can feel like a brain drain.

The longer I write it, the more pressure I put on myself to make sure it’s not the same thing over and over again. And I don’t want to become the noise we seek to reduce.

I worry about interpreting research wrong (it’s happened). Typos and grammar errors (two years ago, I wrote the newsletter the night before my grandfather’s funeral and spelled Arnold’s name wrong). Or making it so nuanced that people don’t get it.

It’s hard for me to admit, but I wake up many mornings rethinking whether I could have written or edited something differently. Or when I get an early-morning text from Ketch, I sometimes worry I made an error before I even read it. That comes from caring about helping all of you and knowing you rely on us.

It’s a good pressure, but it’s still pressure.

And there’s the reality that you can’t please everyone.

Every day, people complain and request longer items with more detail. And other messages want shorter items that are easier to digest (which is why we added the summaries at the end).

It piles up fast, and when you’re buried in it, it gets harder to tell what’s worth your time and what’s ready to publish.

Your replies gave me some clarity back.

Not every item will be for every person. And that was never the goal.

But every item should be worthwhile and meet a standard.

Mike, in his own way, was asking whether mine does. And it’s a fair question.

This newsletter exists to help you get a little better every day.

I hope the tools and tips make a difference.

I also hope I’m getting better alongside you —as a writer and an editor, a father and a husband, a coach and educator — at all of it. That only happens if I’m open about where I’m bad, where I’m good, and the large, messy middle where most of us actually live.

We call this the positive corner of the internet. Positive doesn’t mean praise. It means kindness, support, and respect, with enough accountability and honesty to keep growing.

So the column stays, and so does an open channel for feedback, whether I love it or hate it. That’s why the reply button works on these emails.

Use it when something here lands, and use it when it doesn’t. Hold us accountable, and preferably be kind. Either way, we don’t take for granted that you care and are part of this community.

You thank us all the time, but this week, I wanted to thank all of you, Mike included.

Criticism almost always feels like a verdict when it lands. Give it a little time, and it usually reads more like edits on a draft.

And you’re still a draft. We all are. Drafts can be improved. And that’s one of the best parts of life. -AB

-Adam Bornstein is the co-founder and co-editor-in-chief of Arnold’s Pump Club

The Positive Corner of The Internet
About Arnold’s Pump Club Editorial Standards

We do things a bit differently here, starting with transparency.

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Publisher: Arnold Schwarzenegger​

Editors-in-chief: Adam Bornstein and Daniel Ketchell