This episode of *Science Versus* explores the health impacts of weight cycling, or yo-yo dieting, a common experience for many adults. The host, Wendy Zuckerman, and producer Rose Rimler investigate claims that this cycle harms metabolism, muscle, and overall health. They begin with John Rossi, a drummer who has cycled through weight loss and regain nine times, feeling frustration and self-blame. The science reveals that weight loss triggers hormonal changes that increase hunger and decrease fullness, making maintenance difficult. While metabolism slows as the body shrinks, the dramatic findings from the *Biggest Loser* study are extreme and not typical; most research shows minimal long-term metabolic damage. Muscle loss during cycles may occur more in older adults, but younger people regain muscle and fat proportionally, with no evidence of compounding harm. Mouse studies suggest weight cycling could increase inflammation, but human randomized trials of healthy weight loss programs show clear benefits, such as reduced diabetes risk and lower cholesterol, even if weight is regained. Ultimately, the episode emphasizes that healthy behaviors like eating well and exercising matter more than body weight or fluctuations, offering reassurance that weight cycling itself is not inherently dangerous when approached through sustainable, healthy changes.
Wow! Wow, wow. So it's weird. It is true. It is true that weight cycling
can mess up your metabolism. Not so fast.
Hi, I'm Wendy Zuckerman and this is Science Versus.
Today on the show, why is it so hard to lose weight and keep it off? Plus, what happens to
your body when you lose a bunch of weight and put it back on and lose a bunch of weight and put it
back on? Because the internet is saying that this cycle, which is very common, is actually really,
really bad for your health. But is it true? And just quickly before we get started, I do want to
say that if this is a sensitive topic for you, please take care while you're listening to the
show and we're going to put some resources in our show notes. Okay, to get into the science here,
we have senior producer Rose Rimler. Hello.
Hi, Rose. Hi, Wendy.
Where do we begin?
The first thing I want to do is I want to introduce you to someone I recently talked
about this quite a bit with. His name is John Rossi. He's a musician. He's actually a drummer.
I called him up because he is someone who has struggled a lot with his weight.
I have been weight cycling most of my adult life and it's not fun.
Weight cycling. So this is the term for when folks lose a bunch of weight, put it back on,
lose a bunch of weight, put it back on, right? Is this, this is the new internet term that I guess
in the nineties we were calling yo-yo dieting? Yeah, I think so. I think weight cycling is like
a little bit more, sounds a little more scientific or something. And so John's story is that he
initially lost a lot of weight in his twenties. That was like the first time he ever lost weight.
He lost quite a bit of weight and his appearance really changed.
People, he said, were complimenting him a lot. He was getting a lot of positive attention and it
changed a lot of things for him. He said it changed the way that he dressed.
So he said that before this happened, he was wearing like dark t-shirts and baggy jeans.
And now I was wearing the most like funky pink, cool stuff and skinny jeans. And,
and I was, I was in it to win it. What was your wackiest outfit from that time?
I had, um, so I had a pink t-shirt that I like to wear with a pink, like flannel over shirt,
like a button down over shirt. And I was wearing a pink t-shirt that I like to wear with a pink,
unbuttoned with matching pink sunglasses.
That's not pretty rad.
It was, it was so bright and it was so good. And I, I, I miss it.
He eventually gained back a lot of the weight that he had lost.
And so he put his pink outfit in the basement. So that was the first time, but he's since then
gone through a bunch of these cycles, losing weight, gaining back weight, losing weight,
gaining back weight. And he's not alone. Studies find that up to half of adults in the U.S. have
gone through at least a half of the same thing. And so he's not alone. He's not alone. He's not
one weight cycle. Half of all adults in the U.S. have experienced this. Yeah, it's very common. And
it's also very common for it to happen repeatedly. So another survey found that of people who do
weight cycle, they go through on average eight cycles by the time they're middle-aged. And,
you know, he's right on track for that average. I am currently on my ninth time trying to lose
weight. Wow. And how many pounds do you think that is over the course of your life? I mean,
if I had lost all of this together, I'd be in the negatives. Yeah, you'd be, like, lost your entire
self. Yeah, yeah, yeah. Like, I have lost multiple people, you know, over this time period. In fact,
he says he's lost and put on hundreds of pounds over the last couple of decades. Yeah. You know,
John has worked so hard so many times that when this happens, it just feels awful for him.
Terrible. Like, truly, like, I was failing myself. And I was, I was,
you know, I had succeeded at something and then failed at it, which I think is probably worse than
just never succeeding at something. And it's really hard. It is. I would take every other
challenge in my life and double them if I could get rid of this one. Yeah, I heard similar things
from other people who I spoke to for this episode. Listeners called in and just seemed like there was
a really common theme. I mean, I don't know if it's true, but I think it's true. I think it's
frustration, sadness, and then also a lot of self-blame. Ugh, you know, I've done it again. I
just couldn't help myself or I wasn't paying attention or I wasn't doing what I was supposed
to be doing. I don't know how to get out of this cycle. When I was with a bunch of friends and had
to climb on a scale in front of a bunch of people to be weighed to see if I could ride a ride at a
pace, I was right back up to where it had been, over where it had been before I started Weight
Watchers. Three years before, I was devastated and went into a depression spiral that lasted
for years. Ugh. So people really want to know more about why this happens to them. And in this
episode, we're going to talk about weight loss and regaining weight. So, let's get started.
You're like ruining your metabolism. Right. That you're going to end up with a higher body fat
percentage and less muscle than you would have otherwise. And that you're just, you're going to
be sick. You're going to get diseases like type 2 diabetes, heart disease, that kind of thing.
And you would have been better off if you just never, never tried at all. Kind of is the
implication. Yeah, some people say that. So, we're going to get into all of that. We're going to do
that for John, too. John is a very science-y person, but he says, this one, this is kind of
hard for him to dig into. This one's too close to home. I've read so many things. I've heard so
many things. I just want to hear from people that I trust, like a true scientific look at all of
this. Because I can't. I can't at this point. I really felt like, do-do-do-do-do-do. Rose.
You got your cape? You're a voice we trust. Oh, I have my cape. It's my cape, actually.
Yeah, yeah, yeah, yeah, yeah. I'm just in costume. I'll be the voice. Yes.
The science on weight cycling and is it really killing you? Coming up after the break.
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or visit tramphyaradio.com. Welcome back. Let's find out why it's so hard to lose weight and then keep it off. Because everything's
political these days. It's so hard to lose weight and then keep it off. It's so hard to lose weight
it actually almost feels like the woke thing to say.
is it's so hard to lose weight and keep it off.
And the people who say it like it is,
they'll tell you if you diet and keep that diet,
you can lose weight, you know.
So is this just wokeness and unwokeness gone mad
or give me some actual data here?
I mean, if it were that easy,
we wouldn't have things like the National Weight Control Registry,
which is set up to specifically find people
who can lose a lot of weight and keep it off
and track them and study them.
That's how rare it is to lose a significant amount of weight
and keep it off for longer than like a year.
And one person I spoke with, Elena,
she's an actor from New York.
She had heard about this registry.
That was like my goal was like,
I want to be in the registry.
So I guess like, you know,
if people do lose a bunch of weight and keep it off long term,
is there anything?
What's special about them?
Are they addicted to exercise and psychotic about what they eat?
And that's the only way you can do it?
Great question, Elena.
What's happening?
Is that what's special about them?
Well, the scientists behind the registry have shared
some things that these people seem to have in common.
Some of them are kind of random,
like they say, you know,
like they tend to eat breakfast.
Oh.
So take with that what you will.
They also exercise a lot.
On average, an hour a day, these folks.
An hour a day.
Yeah, that's committed.
Yeah.
And to Elena's point, like, are they,
I think she said psychotic about what they eat.
I don't know if they're psychotic about it,
but they're very careful.
The researchers said that they exhibit,
quote, a high level of dietary restraint.
So it really becomes their whole life.
It has to become very important.
Yeah.
Okay.
So then why is it,
why does it take so much restraint?
Why does it take so much?
That's right.
Yeah.
So there's a few reasons.
One is that when you lose weight,
your hormones change.
Your hunger hormones increase
and your fullness hormones decrease.
So if you, to this point of,
if you just stayed eating a certain number of calories
that allowed you to lose weight in the first place.
If you just stayed on that diet forever,
you could keep this weight down.
Actually staying on that diet forever
becomes harder and harder.
Yes, it becomes harder and harder
because your body is nudging you
towards eating more to counteract that weight loss.
And there's a really cool study
I want to tell you about that shows this.
And shows just how like below conscious awareness
this is happening.
So in this study,
researchers gave people a drug
that pulls sugar out of your body.
Into your urine.
So you end up peeing out a lot of sugar.
This is in the diabetes world, this drug.
Okay.
Because you're peeing out a lot of sugar,
you lose weight.
You're like excreting calories.
So people on this drug tend to lose weight.
If you tasted your urine, it would be sweet?
Yes.
Okay.
You know, if you run out of honey, you know.
It's good to have a little backup.
This was a controlled study.
They also had people take a placebo pill.
They had another group on a placebo pill.
So if you were in the study, you didn't know
if you were given a pill
that was causing you to excrete more calories or not.
Okay. Uh-huh.
Then they followed people to see kind of like
how they ate after that.
And they found that the people on the drug
without knowing that they were losing weight
started to eat more.
The people on the placebo drug
know that it wasn't that kind of change.
Right.
So just like those hunger hormones,
kicking in, they were just a little bit more hungry.
Just a little bit.
Yeah, but it adds up.
So this is one reason why it's so hard.
Your body wants to conserve calories,
which for most of human history,
we were hunting for food.
Food was hard to get and that's how humans evolved.
And now it's very different.
So it does make perfect sense
that there are these things beyond our control
in our body that are pushing us towards weight gain
rather than weight loss.
And I think this is one of the things
why it's so confusing and frustrating for people
because they're still eating below what they want to eat.
They're still like restricting their dietary intake.
I heard someone give a talk where they said
keeping off weight is like holding a rubber band
really tight.
So you have to keep holding it.
And it's very hard to do that.
Eventually you relax a little bit.
And another thing that people bring up
is about metabolism.
This idea that your metabolism changes
from weight loss.
And that's another factor.
That's right.
Because the people who say that weight cycling is dangerous,
one of their arguments was that
it actually breaks your metabolism in the end, right?
Right.
Therefore making it even more difficult to lose weight.
Yeah.
So let's dive into metabolism.
Yeah.
I talked about this with Faden Magkos.
He's a professor in the nutrition and exercise department
at the University of Copenhagen.
And the first thing he told me was that,
yes, your metabolism,
will get slower when you lose weight.
When people lose weight,
they burn fewer calories.
And this happens both at rest and during exercise.
And that is completely normal
because a smaller body actually needs fewer calories
to sustain its function.
So it is true.
It is true.
As you get smaller,
your metabolism does slow down.
Yes.
So basically what our metabolism is mostly doing
is running a complicated machine.
The size of that machine,
that machine matters.
If you're a bigger machine,
you need more energy.
You need more calories.
If you're a smaller machine,
fewer calories plus energy.
And so as people lose weight,
they have a smaller machine to run
and they need fewer calories.
And that in itself could be challenging
to sort of dial down your calories more and more.
All right.
So then can we take it one step further?
Because the internet always does.
Yeah.
If you then weight cycle,
does over time that process break that machine of ours?
Yes.
And ultimately break your metabolism in some way.
So the people who talk about this,
they often talk about this one particular study.
Let's talk about the biggest loser study.
The biggest loser study?
It's the biggest loser study.
The biggest loser.
Remember that, Wendy?
The reality show?
Yep.
The reality weight loss competition.
Uh-huh.
Yes, of course I remember it.
Yelling.
Lots of yelling at people.
Lots of yelling.
Dan, no!
I can't.
Yes, you can.
Get back to work.
Come on!
Dina, come back, Dina.
You're acting pathetic.
It was really intense.
It had people do hours of exercise a day,
like two or three hours a day,
while they were cutting calories as well, significantly.
It was mad.
It was mad when you think about that moment in history.
And then everyone would go for the weight,
where they would measure themselves,
and everyone would line up.
Yeah, the public weigh-in.
The public weigh-in.
Yeah.
It's just so medieval.
It's brutal.
And it was just, wow.
Wow, okay.
We were doing that.
Why are we talking about it on Science Versus?
Because one good thing, interesting thing,
came out of that show, science.
We have some science from that show.
Because one season, scientists actually followed contestants
before and after they were on the show,
measuring their resting metabolic rate.
So they did that before they started the show,
before they lost weight,
and then after the show, when they had lost weight.
And they lost a lot of weight.
On average, this group of people,
just like 16 people,
they lost about a third of their body weight on average.
Wow.
And so, did their metabolism slow down as expected?
So it slowed down, of course, because they're smaller.
Machines were smaller.
But then the question is, when they put the weight back on,
did they?
What happened next?
They did.
So over the course of six years,
most people put some of the weight back on,
or all of it back on.
And the scientists circled back.
They got back to them after these six years,
and they measured their resting metabolism again.
And so you would expect if the weight had come back,
then the metabolism would bump up as well, right?
That's right.
So what happened?
They didn't find that.
These folks, their metabolism, on average,
was still suppressed years later.
By how much?
Well, here's Faithan.
So their resting metabolic rate,
it was lower than predicted by about 500 calories per day.
What is that in food?
It's a Big Mac.
Okay.
Wow, a Big Mac a day.
That's how much their metabolism had dropped on average.
Right, meaning like,
next to someone who hadn't had this experience,
but was sort of the same size.
Yeah.
That other person could eat a whole extra meal, essentially.
Yeah.
Per day than they could.
Oh, wow, wow.
To stay the same weight.
So it's weird.
It is true.
Not so fast.
Okay.
This is a weird study.
It's small.
What people did is quite extreme.
We have other studies
that are a little bit more in keeping with the reality
of what happens to most people.
And bigger.
More people in the studies.
Great.
Yes.
This was just 16 people, right?
Okay.
So what else?
What do other studies show?
Some studies do also find some effects,
some like suppression of the metabolism.
It's not just.
the biggest loser.
Okay, right.
But the biggest loser
found the biggest,
most extreme result.
Most of the studies
find something much smaller.
And in fact,
a meta-analysis found
it was quite a small amount
on average.
The metabolism
lowered by a small amount
on average.
Yeah.
And it's actually so small
that Fathin argues
that it actually could be
within the margin of error
for what these measurements
can actually detect.
Uh-huh.
So this is good news
for John,
who's been weight cycling
nine times, right?
It suggests he hasn't
broken his metabolism, right?
Yeah, yeah.
And I called him actually
after we talked the first time
after I'd done some research,
I called him back
and I told him
about some of the science here,
including this metabolism finding.
I've been told by
so many people
my whole life
that I, you know,
that I am hurting myself
and I am causing myself
these, like,
long-term issues and. From the weight
going up and down?
Yeah, yeah, yeah.
To the point where
it has scared me
to try losing weight sometimes.
And I'm like,
no, what if I'm doing
more damage?
And so that's
really encouraging.
Science to the rescue.
No, we're such nerds.
I know.
But it's nice, it's nice
because science doesn't
always come to your rescue,
you know?
It does not
and sometimes
it really kicks your ass, so. Okay, so the next thing
I want us to look at
or look into is
what happens to your muscles
when you
lose weight
and then put it back on
and lose weight
and put it back on
because the way
some people talk about it online,
it's almost as if
your muscles will disintegrate
over time.
Do you know what I mean?
This whole internet's
so extreme.
What is happening
to your muscles?
It's extreme.
What people do say is that,
you know,
when you lose weight,
you lose some of your muscle
and then you,
when you gain it back,
you don't get back the muscle
or not as much.
You get back,
more fat.
Okay.
Yeah, yeah, yeah.
And that can happen.
Uh-huh.
So,
there is a study
in North Carolina
where researchers
follow people
who went through
a weight cycle
over about a year,
lost weight,
gained it back.
They found that people
lost 74%
of the weight
as fat,
but when they
gained weight back,
88% came back
as fat.
Right.
It's not a huge difference,
but it's definitely there,
right?
It's there.
Yeah.
And you could,
imagine
if you have that difference
over time
with weight cycling,
you're going through
this nine times,
the fear would be
that then it would compound
and you would,
with every weight cycle,
lose more and more muscle.
Is that what we see?
Well,
not every study finds this.
So,
a very similar study
Oh, Rose,
you've done it to me again.
Look,
you gotta read
more than one study.
And,
you gotta tell me.
Then you get,
the,
stop.
Alright,
so what's the,
your guess?
Okay.
Don't tear me.
Well, let me tell you
about this other study.
Yeah, tell me about
this other study.
Great.
This one was from Germany.
Okay.
Researchers similarly
followed people
when they lost weight
and gained it back.
Uh-huh.
They gained pretty much
the same amount of fat
as they had initially lost.
Same amount of muscle.
No real difference.
So,
what,
you might ask me,
is the difference
between those two studies?
Yes.
That is what
you might ask me.
I will ask you.
What is the difference
between those two studies?
Um,
the difference was age.
Mm-hmm.
So,
in the study where people
gained back more fat
than they had lost,
they were older.
They were people
in their 50s,
60s,
and 70s.
Mm-hmm.
While in the study
where people
did not really see a difference,
they gained back
just as much muscle
as they had lost,
they were younger.
20s,
30s,
and 40s.
Mm-hmm.
And we know
that over time,
you lose muscle.
We all lose muscle
whether we're
going through
weight cycling or not.
That is just one of the
ingloriousness
It just happens to everybody.
of aging.
Yes.
So,
so this isn't such a big deal
then,
you think?
I mean,
it's,
it's,
that's,
this is a tough one
because,
and I have spoken
to some researchers
who are genuinely
worried about this.
So that's a legitimate concern,
but
the way people
talk about this online,
that you're like
doomed
to ruin your body
composition,
um,
I didn't see
any evidence
that that's the case.
But yeah,
I mean,
and then your question,
Wendy,
of like,
does this compound?
Like,
does with each successive
weight cycle,
you lose more muscle,
you gain more fat?
I can't really answer that
because we don't really
have those studies.
We have very few studies
that follow people
for more than one weight cycle
and that's true for all this.
Mostly,
it's just one,
one round of weight cycling.
What did John
think about this?
He,
you know,
John said he wasn't,
this wasn't something
he was actually
that worried about.
Because from his own experience,
he was like,
no,
I,
when I lose and gain weight,
it doesn't really affect,
it doesn't seem to affect
the way I can
operate my body.
Like,
he talked about being a drummer.
I trust my arms.
Whatever size I am,
like,
I trust that my muscles
will do the same thing.
Yeah.
So,
that does make sense.
I wasn't too worried about that,
but I mean,
it's nice.
Yeah.
Like,
I wasn't worried about it,
but cool,
I'll take it.
All right,
Rose,
off to the break.
We're going to talk about,
like,
health more broadly.
Inflammation,
diabetes,
heart disease,
does weight cycling
make all of that worse?
Coming up.
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Welcome back.
Today on the show,
we're talking about
weight cycling
or yo-yo dieting.
What happens to your body
when you lose a bunch of weight
and put it back on,
lose a bunch of weight
and put it back on.
The internet says that
this can over time
make you sicker,
and sicker,
and we're looking into that claim.
And one idea
that I really want to probe
is around inflammation
and that this weight cycling
can ultimately increase
the amount of inflammation
in your body.
Tell me the science, Rose.
This comes from
what we know about
fat tissue on our bodies.
So, you know,
you and I, Wendy,
and maybe our audience
probably assumes
that
fat,
the fat on our bodies
is inert.
It's just like squishy stuff
that's there to act as padding
or maybe, you know,
provide a little extra energy
if we need it.
And actually,
that's what scientists
used to think too
until like the mid-90s
when they started to realize
that fat is actually
a very active tissue
in the body.
And one of the ways
it's active
is that
it's actually full
of immune cells.
I spoke about this
with Alyssa Hayes,
she is currently
a professor
at the University of Texas
Southwestern Medical Center.
Every single immune cell
that's known
to immunologists
exists
in our fat.
This is especially true
for the fat
that collects
around our organs,
visceral fat,
which you're probably
familiar with.
The more dangerous fat,
that's the fat
scientists are worried about.
Yeah, when fat
collects around your organs,
that's bad.
And one reason is
because
that's not really
a place where you can
store fat.
It's like
not set up.
The body isn't really
set up to
support the fat there.
And so there isn't
really like good
blood supply
for those cells,
those fat cells
in that area.
And so they get
like stressed out.
They don't get
enough oxygen
and they like
malfunction
and they even die.
So then there are
these white blood cells
called macrophages
that have to go in
and clean up
the debris
from those
dead and dying cells.
But then they can
get overwhelmed.
So here's
Alyssa.
out signals that say, hey, other immune cells, other macrophages, come help us out here. We've
got to take care of this debris, this dead cell. Aha. So then you get more, basically more and more
inflammatory cells, right? More and more macrophages then calling out more and more
immune cells to come and help. And you just get this kind of vicious cycle.
Mm-hmm. But then the question for us today is, does that get worse if you lose weight
and put it back? Right. So that's what Alyssa wanted to test. So she set up this mouse model
where she had the mice gain weight by feeding them a high-fat diet for nine weeks. Then she
switched them to a low-fat diet. Mm-hmm. Was that kind of, is that like putting the mice on a crash
diet? Yeah, it definitely is.
And then she yelled at them, like in the biggest loser. Yeah. And she made them go round and round
and round in their little hamster wheel. Yes. Yes. For hours and hours. Run, run. And televised it.
Yeah. So then to have them go through like a whole cycle, she had the mice, she put them back
on a high-fat diet for another nine weeks. They gained weight again. Uh-huh. Checked on their
immune cells. Mm-hmm. And what she found, especially regarding this type of immune cell
called the T-cell, was surprising. The T-cells were elevated even further
than the high-fat diet. Mm-hmm.
In the weight cycled compared to the obese only, despite the fact that they were the exact same
weight and had the exact same visceral fat mass and total body adiposity. So these were even more
like agitated. The mice were worse off in terms of what their T-cells were doing
than the mice, control mice who had never weight cycled but had been obese basically the whole
time. Mm-hmm.
And the immune cells didn't like it. They're going back the cycling. Uh-huh. And so this is
how Alyssa puts it. The body remembers. The immune system remembers our body weight and
gains and losses in that. Uh-huh. The body remembers. What's going on there?
We don't totally understand all this, but it seems like something about this, like the stress,
the weight.
The weight gain, the weight loss is like turning on the immune system in a way that's hard to turn
off. And that could be leading to some kind of chronic inflammation, which we know is bad for us
in all kinds of ways. Mm. We said science isn't always your friend. No. Do we know why this is
happening? And obviously this was just a study in mice. You're going to now give me another study
where they found something totally different?
Well, I mean.
Wait, are you really going to give me another study that found something different?
Right.
Yes and no. Okay.
You're such a science tease.
So after looking at this study in mice, I wanted to look at studies in people.
Thank you.
And I did find, along these same lines, I did find studies that compare people who have weight
cycled versus people who have not weight cycled, but they both started out at kind of the same
weight.
Yes, yes, yes.
And were similar in other ways.
Mm-hmm.
And what those studies often find is that the weight cyclers have worse health outcomes than
those who haven't weight cycled.
In what way?
These studies have found a higher risk of heart failure and higher risk of death, actually.
A couple studies.
Wow.
So I don't want to leave things there, though.
Uh-huh.
And the reason is, you know, those studies are not bad studies, but they can't answer
some basic questions here. So, like, they're just observing what happens between one group
and another.
Mm-hmm.
They can't say, like, weight cycles.
Mm-hmm.
Mm-hmm.
And why does weight cycling cause people to die or to get heart failure?
Got it.
Got it.
We need a different kind of study for that, a randomized control trial.
Sometimes we don't have anything else.
Yes.
Yeah.
But in this case, we do.
Okay.
We have some randomized control trials that could help us.
Uh-huh.
Tell me about it.
So I talked about this with Jamie Hartman Boyce.
She is an associate professor of health policy and management at the University of Massachusetts
Amherst.
Mm-hmm.
And she wrote a review paper looking at studies where people lost and then regained weight
after weight.
After going through what are called supervised weight loss programs.
Mm-hmm.
Eating a bit less, you're at a calorie deficit, and you're exercising more.
So we're not looking at people who are, like, on a juice cleanse for six weeks.
Yeah.
Yeah.
We're looking at people who are, like, eating more vegetables and moving their bodies more.
So Jamie's question was, how does the health of these people who have lost weight in this
healthy way gain much of it back?
How does it compare to people who have never lost weight?
Who are the control groups?
Yeah.
Great.
And one of the things we found was that even if you regained the weight back, right?
So even if you started a certain weight, you did your diet and exercise program, you stopped
it, you went back to your starting weight, compared to someone who had stayed at a stable
weight the whole time and not done that program, you were still less likely to get type 2 diabetes.
And it wasn't just diabetes.
It was also lower cholesterol and lower blood pressure.
Why was white cycling healthy?
In this case.
It seems like it could come down to how people lost the weight.
Making healthy changes, getting a little more exercise, eating more vegetables.
Even if people aren't able to keep up those new habits forever, the period of time where
they were doing those healthy habits, which resulted in weight loss, that's what was good
for them.
But these other studies, we don't know how or why they lost the weight.
And then with the mice, you know, it was like a crash diet.
Right.
This was like healthy changes resulting in weight loss.
So, is it even about the weight loss at all, or it's just that for a portion of the study,
these people were eating lots of vegetables, moving their bodies, and that's what was good
for them, whether or not they lost weight or not?
That's one.
Yeah.
I think that's a fair interpretation.
I mean, there's a lot of nuance here, but it does make sense if you think about, if
you know the broader literature about weight and health.
So there's a study.
There's a study I love.
It's a big survey, like 12,000 people were in it.
They asked about healthy habits.
So like, how much fruit and veg do you eat?
Do you exercise regularly, smoking, drinking?
And these were people of all kinds of weights.
Yes.
All kinds of weights.
And they tracked them over time, and what they were measuring was all-cause mortality.
So like, that's the big one.
Like, are you more likely to die?
They found that the thing that mattered the most for, you know, death was not your weight.
Not your weight, but the healthy habits that you did.
So if you were someone who your BMI technically puts you as obese, but you have all these
healthy habits, you were just as likely to not die as a person whose BMI was normal and
did those healthy habits.
What these studies are suggesting is if you're doing healthy things, that's the key.
Yes.
And you have a lot more control over that than you have of your body size.
So it makes more sense to focus on that.
And that's what Jamie said as well.
So I think the data is very clear that if, like, what we're trying to do is improve our
health and well-being, right, then, you know, if we eat healthier, we exercise more, regardless
of what happens to our weight, and one of those things that can happen is that we lose
weight and regain it, we are doing something good for ourselves, okay, and for the people
who love us, who want us to stick around for longer.
So when I told John that it's the healthy behaviors.
more than the weight that really matters, this is what he said.
Wow.
That's really cool.
That's great.
Science.
Back to being your friend.
But it was also, there's something I think about it that was slightly annoying to John,
because it made him think of, like, all the bull he's had to sort through and all the
people saying, like, oh, if you, if your weight fluctuates a lot, you're going to really harm
your health.
Those beliefs have been so common and so repeated over and over and over.
That it shows me that, you know, people don't know what they're talking about with this
stuff all the time.
And it's another nice reminder to not let other people shape me in a literal sense in
this case.
And that I should, I should worry more about, you know, what I think and what the science
says than what people tell you, you know?
So what does this mean for that fabulous pink outfit that John's got?
I did ask about that.
Did you?
Yeah.
You said your confident, wacky outfit was like, I think you said it was like, was it
hot pink?
Yeah.
Oh, my gosh.
So much hot pink.
And skinny jeans?
Yep.
Reflecting on that, it strikes me as a very early 2000s outfit.
So what would the, let's say you get that burst of confidence and creativity and you
want to express yourself through wacky dress.
Yes.
What does the 2026 version of that look like?
Well, 100% goofy animal shirts, always.
I just, I love animals so much now.
And probably still skinny jeans because I don't care if they're in style or not, my
butt looked great in those jeans.
That's science versus.
Thanks, Rose.
How many citations are in this week's episode?
This week, there are 66, and if people want to see them in all their glory, where can
they go?
If you want to check out the transcripts, find that link to the transcripts in our show
notes.
Thanks, Rose.
Thanks, Wendy.
This episode was produced by Rose Rimla with help from McKetty Foster.
Wendy Zuckerman, that's me, is our executive producer.
We're edited by Blythe Terrell, fact-checking by Diane Kelly,
mix, sound design and video editing by Bobby Lord,
music written by Bobby Lord, Bumi Hidaka,
So Wiley, Emma Munger and Peter Leonard.
Thank you so much to all of the experts that we spoke to for this,
including Dr Heidi Silver and Dr Andrea Rossi.
A special thanks to Jennifer C. Wolfe and Sasha Boryshenko.
A big, big thanks to all of the folks who called in
to tell us about their weight cycling experiences.
Thank you so much.
It means so much to us that you trust us to tell us your stories.
So thank you so much.
Science Versus is a Spotify Studios original,
so listen to us for free on Spotify or wherever you get your podcasts.
We're all over.
We're on YouTube, we're on Apple.
If there's podcasts there, so are we.
Like and subscribe, follow, do all that stuff.
And get in touch with us.
We're also on TikTok and Instagram.
All the ways to get in touch are in the show notes.
I'm Wendy Zuckerman.
Back to you next time.
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Podcast Summary
Key Points:
Weight cycling, also known as yo-yo dieting, is common, with up to half of U.S. adults experiencing it, often multiple times, leading to frustration and self-blame.
Losing weight is hard because the body counteracts weight loss by increasing hunger hormones and decreasing fullness hormones, making it difficult to maintain weight loss.
Metabolism slows with weight loss due to a smaller body size, but evidence from the "Biggest Loser" study showing long-term suppression is extreme and not representative; most studies find only small, possibly insignificant effects.
Muscle loss during weight cycling varies by age; older adults may regain more fat than muscle, while younger adults typically regain both proportionally, with no compounding harm evident.
Mouse studies suggest weight cycling may increase inflammation and immune cell activity in fat tissue, but human studies show mixed results.
Observational studies link weight cycling to higher risks of heart failure and death, but randomized controlled trials of healthy weight loss programs show benefits, including lower diabetes risk, cholesterol, and blood pressure, even if weight is regained.
Healthy habits, not weight alone, are key to health outcomes; focusing on diet and exercise is more beneficial than worrying about weight fluctuations.
Summary:
This episode of *Science Versus* explores the health impacts of weight cycling, or yo-yo dieting, a common experience for many adults. The host, Wendy Zuckerman, and producer Rose Rimler investigate claims that this cycle harms metabolism, muscle, and overall health. They begin with John Rossi, a drummer who has cycled through weight loss and regain nine times, feeling frustration and self-blame.
The science reveals that weight loss triggers hormonal changes that increase hunger and decrease fullness, making maintenance difficult. While metabolism slows as the body shrinks, the dramatic findings from the *Biggest Loser* study are extreme and not typical; most research shows minimal long-term metabolic damage. Muscle loss during cycles may occur more in older adults, but younger people regain muscle and fat proportionally, with no evidence of compounding harm.
Mouse studies suggest weight cycling could increase inflammation, but human randomized trials of healthy weight loss programs show clear benefits, such as reduced diabetes risk and lower cholesterol, even if weight is regained. Ultimately, the episode emphasizes that healthy behaviors like eating well and exercising matter more than body weight or fluctuations, offering reassurance that weight cycling itself is not inherently dangerous when approached through sustainable, healthy changes.
FAQs
Weight cycling, also called yo-yo dieting, is when a person repeatedly loses weight, gains it back, loses it again, and so on. It's common, with up to half of U.S. adults experiencing at least one cycle.
No, not permanently. While some studies, like the Biggest Loser study, show a slowed metabolism, most research finds only a small effect, possibly within measurement error. Your metabolism slows when you lose weight because a smaller body needs fewer calories, but it doesn't get 'broken' by cycling.
Evidence is mixed. Some studies show older adults regain more fat than muscle after a cycle, but others, especially in younger people, find no difference. There's no clear evidence that repeated cycles compound to ruin body composition.
Some observational studies link weight cycling to higher risks of heart failure and death, but they can't prove causation. Randomized controlled trials of healthy weight loss programs show that even if weight is regained, people still have lower risks of type 2 diabetes, lower cholesterol, and lower blood pressure compared to those who never lost weight.
When you lose weight, your hunger hormones increase and fullness hormones decrease, pushing you to eat more. Your metabolism also slows because a smaller body needs fewer calories. These changes are largely below conscious awareness, making it hard to maintain weight loss.
Animal studies suggest weight cycling can increase inflammatory immune cells, like T-cells, in fat tissue. However, human studies are limited, and healthy weight loss programs don't show long-term harm, suggesting the way you lose weight matters.
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