Video podcast Gesundheit braucht Verstand
Yo-yo effect:Why fat cells remember the old weight
You lost weight, and a few months later the old weight is back? This episode is about a study by ETH Zurich that found a memory of earlier phases of excess weight in fat tissue. Here you will learn what the study shows and what it does not, what role leptin, sleep and the microbiome play, and where breathing, swallowing and head balance fit into the picture.
Does this sound familiar?
Lost weight, kept at it, and still the weight is back?
What applies to you?
Tap whatever applies to you.
If several points apply, you are not alone. The yo-yo effect has biological reasons. Some of them you cannot influence directly, others you can. This distinction is what this page is about.
What the study showsWhere you can startThe key points at a glance
- After a diet, weight returns in many people. A study by ETH Zurich found changes in fat tissue that were still detectable two years after significant weight loss. In mice, they could be demonstrated as an epigenetic memory of the fat cells.
- Then there are the hormones. After weight loss, the satiety hormone leptin falls, the hunger hormone ghrelin rises, and both remain shifted for more than a year. Short sleep and the microbiome also play a part.
- The memory of fat cells cannot yet be erased. What you can influence is how much energy your other cells use, and how you eat, sleep and breathe. In our view, breathing, swallowing and head balance are among these foundations.
Video
Yo-yo effect: why your body does not forget its old weight
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Video podcast
The episode in chapters
In just over 20 minutes, Dr. Klaus Berndsen explains in his video podcast “Gesundheit braucht Verstand” (Health needs reason) what lies behind the yo-yo effect. Here you will find the chapters with their timestamps.
- 00:00
Introduction
What it is about: a new study from Switzerland.
- 00:48
Why does the weight come back?
You lost weight, and the old weight returns.
- 01:59
The memory of fat cells
White and brown fat cells that remember something.
- 03:52
Epigenetics
External influences control how genes are read.
- 06:11
Fat memory simply explained
Marks like sticky notes and a tightly packed rucksack.
- 07:29
Leptin
The satiety hormone and why it goes unheard.
- 08:43
Short diets
Why the first success often does not last.
- 09:15
Procedures for weight loss
Stomach reduction, liposuction and medication.
- 11:06
How can you lose weight?
Letting other cells do the work, moving in a joint-friendly way.
- 13:25
Oxygen
The fuel of cellular respiration.
- 14:31
Mouth breathing is not innate
Learned, not inherited.
- 16:20
The nose as a laboratory
What happens when you breathe through your nose.
- 17:50
The microbiome
Trillions of bacteria helping to process food.
- 19:42
Digestion begins in the mouth
Chewing, mixing with saliva and swallowing.
The article below puts the statements of the episode into context and adds the current state of research, including where the video simplifies.
The yo-yo effect
When the weight comes back: not a sign of weakness
Many people manage to lose weight. Keeping the new weight for years succeeds much less often.
The yo-yo effect describes the pattern in which body weight rises again after a diet, often back to the starting value. Many of those affected experience this as a personal failure. Research paints a different picture. The body defends a weight it has once reached, and it does so with several mechanisms at the same time.
from the USA with at least two years of follow-up were evaluated in a meta-analysis. Five years after a weight-loss programme, participants had on average maintained just over 3 kg of their weight loss1
per day was how far the resting metabolic rate of 14 participants in a weight-loss show was below the starting value six years later. On average they had regained 41 kg of their weight loss2
So the body saves energy, and it remembers earlier states. If you follow this logic, a diet alone has poor prospects. It reduces energy intake, the body responds with more hunger and more economical consumption, and the pattern of sleep, breathing and eating behaviour remains as it was. Where the memory for this is located was an open question for a long time. In 2024, a study by ETH Zurich provided part of the answer. It is the occasion for this episode.
The study
Fat tissue with a memory: what the ETH study shows
The work by Laura Hinte, Daniel Castellano-Castillo and colleagues was published in December 2024 in the journal Nature. It has two parts, one with humans and one with mice.
In the first part, the team examined tissue samples from the abdominal fat and the subcutaneous fat of people with severe excess weight, once before stomach surgery and again two years afterwards. Only those who had lowered their body mass index by at least a quarter were included. Samples from people who had never been overweight served as a comparison. Many genes that were read differently in excess weight were still read differently after the weight loss3.
after the surgery, a large part of the changes in fat tissue that had developed with excess weight was still detectable3
reduction in body mass index was the minimum requirement for inclusion in the analysis3
of high-fat feed were enough for formerly overweight mice to gain weight faster than animals without this history3
In the second part, the researchers fed mice a high-fat diet and then switched them to normal feed until their weight was normal again. In the fat cells of these animals, chemical marks on the genome persisted and made the cells work differently. They responded less well to metabolic signals, and when food was plentiful again the animals gained weight faster.
Fat tissue does not forget how it used to be.That is how the core of the study can be summarised. The authors speak of a memory of excess weight that may help explain the yo-yo effect.
Important for putting this into context: the epigenetic marks themselves were only measured in mice. In the human samples this was not yet technically possible; there, altered gene activity was shown. The groups were small, and the authors themselves write that their data do not yet conclusively prove a causal link with the yo-yo effect.
Epigenetics
Epigenetics simply explained: sticky notes on the genome
The genes themselves do not change when you gain weight. What changes is which genes are read and how strongly.
Every cell in your body carries the same genome. The fact that a fat cell works differently from a muscle cell depends on which sections are read. This is controlled, among other things, by chemical attachments to the DNA and to the proteins around which it is wound.
External influences such as diet, exercise or stress can change these marks. Fat cells that were packed full for a long time carry different marks from fat cells that never experienced this.
Like sticky notes in a cookbook
Imagine your genome as a thick cookbook. The recipes stay the same. But someone has stuck notes inside that highlight some pages and cover others. After years of excess weight, the fat cells have notes stuck at the recipes for storage. If you lose weight, many of these notes stay stuck, and the next time food is plentiful the cell opens these pages more quickly.
How long does this memory last? The episode mentions more than ten years. The figure does not come from the ETH study, which covers two years, but from the lifespan of fat cells, as determined by a Swedish research group4.
of fat cells are renewed each year, at every adult age and at every body weight. Their number remains the same, even after significant weight loss4
is therefore how long it takes, mathematically, for the stock to be replaced once. A fat cell can carry its marks for that long
Leptin and ghrelin
Hunger and satiety: when the signals no longer get through
Fat cells do not only store energy. They also send messages to the brain.
The most important signal is the hormone leptin. It is produced in fat tissue and tells the brain how full the stores are. Its counterpart is ghrelin from the stomach, which triggers hunger. The more fat is stored, the more leptin circulates in the blood.
In theory, excess weight should therefore dampen hunger. In many of those affected, it does not. As early as 1996, a study with 275 people showed that people with excess weight had around four times as much leptin in their blood as people of normal weight5. The authors concluded that many of them had become insensitive to their own leptin. This is referred to as leptin resistance.
In the video, Dr. Berndsen compares this with insulin resistance. A signal that is constantly loud eventually goes unheard. In addition, when you lose weight the amount of leptin falls, and the brain interprets this as a shortage.
lost an average of 13.5 kg in ten weeks in an Australian study. A year later, leptin and ghrelin were still shifted, and the participants were hungrier than before the diet6
The diet works
The fat cells empty, the amount of leptin in the blood falls.
The brain signals a shortage
Less leptin and more ghrelin are interpreted as scarcity.
Appetite increases
Hunger grows, and the body additionally saves energy.
The stores fill up
Fat cells with a memory readily take up what is on offer.
The old weight returns
In many people back to the starting value, and the cycle can begin again.
Context
Surgery, weight-loss injections, liposuction: what they change and what they do not
In the episode, Dr. Berndsen also talks about procedures that change weight from the outside. Here we classify them, with their consequences and with what they do not touch.
The stomach does not have its size for nothing. Stomach surgery intervenes in the digestive tract and, like any major procedure, involves risks, including complications, follow-up operations and lifelong medical supervision14. It changes the route of the food, but not the pattern of hunger, sleep and breathing that helps determine weight, and in the ETH study the fat cells still bore traces of the earlier phase two years afterwards3.
Weight-loss injections dampen hunger as long as they are injected. In the large approval study with semaglutide, nausea and diarrhoea were the most common side effects15. After discontinuation, a large part of the weight lost came back in the extension of the study16. The injection treats the symptom; it does not change the pattern behind it.
of participants on semaglutide discontinued treatment because of gastrointestinal complaints, compared with 0.8 % on placebo. The study included 1,961 adults15
of the weight lost had been regained by participants one year after stopping semaglutide, evaluated in 327 people16
Liposuction changes the body shape in one place. It does not change anything about hunger, satiety hormones, sleep and habits, and the body keeps the number of fat cells essentially stable4. In our view, where the weight is stored again afterwards is decided by the same pattern as before.
What acts from the outside
- Surgery reduces the size of the stomach or changes the digestive route
- Medication dampens hunger for as long as it is taken
- Liposuction removes fat tissue in one place
- All three belong in medical hands and can be useful in severe excess weight
What the body contributes itself
- Muscles and organs use up the stored energy
- During sleep, the hormones for hunger and satiety are adjusted
- Thorough chewing can dampen hunger
- In our view, breathing, swallowing and head balance form the foundation
The two sides are not mutually exclusive. Anyone who has had surgery or takes medication can make use of their own levers just as well.
If you take medication for weight loss or for diabetes, do not stop it on your own and discuss any changes with your treating practice.
Levers
Using the energy expenditure of the other cells
The memory of fat cells cannot yet be specifically erased. The ETH authors see this as a goal for future research. Until then, it is worth looking at the cells that use energy.
Fat cells store, muscle cells consume. Dr. Berndsen places this idea at the centre of the episode. If the fat cell wants to hoard energy, you let other cells draw more of it. Muscles that work also take their energy from the fat stores.
more physical activity than before the weight-loss show was seen in the participants who had maintained their weight six years later. In those who had regained weight, it was 34 %7
of the differences in weight after six years were explained by physical activity and energy intake together. Only physical activity was associated with weight regain, not the amount of food7
With 14 people, the group was small. Competitive sport is not needed for this; with severe excess weight, the joints are quickly overloaded. More important than intensity is that exercise becomes part of everyday life.
Swimming and water aerobics
The water carries part of the body weight, yet the muscles still work. This spares the joints.
Walking and cycling
Can be built into journeys you make anyway and increased in small steps.
Movement in small doses
Stairs instead of the lift, standing up while on the phone. Even small movements use energy.
Breathing and sleep
Nasal breathing, sleep and appetite: what is proven
Oxygen is the fuel of cellular respiration. That is why, in the episode, Dr. Berndsen emphasises which route the air takes into the body.
The nose is more than an air duct. It warms, humidifies and cleans the air we breathe. In addition, the paranasal sinuses produce nitric oxide in very high concentrations8, a messenger substance that widens blood vessels and reaches the lungs with nasal breathing.
A Swedish research group measured what difference this makes. In six out of eight healthy people, the oxygen pressure measured at the skin was 10 % higher during nasal breathing than during mouth breathing9.
No study shows that nasal breathing makes you slim.We say that openly. In our view, however, nasal breathing creates a precondition for oxygen supply and sleep to work as they are designed to.
from a sleep study in Wisconsin were examined in the sleep laboratory, and their hormones were measured in the morning on an empty stomach10
less leptin was predicted by the statistical model for five instead of eight hours of habitual sleep, plus 14.9 % more ghrelin after five instead of eight hours of sleep on the measurement night10
So people who sleep briefly or restlessly tend to have a greater appetite, regardless of body weight. In our view, this closes a circle. Night-time mouth breathing and snoring disturb sleep in many people, and additional tissue around the neck can narrow the airways further when lying down. You can find out more in the article on snoring and sleep apnoea.
Mouth breathing at night
The mouth is open, the tongue sinks backwards, the air bypasses the nose.
Restless sleep
Snoring and brief arousals make sleep shallower.
Shifted hormones
Less leptin, more ghrelin, appetite during the day increases.
More weight
Additional tissue narrows the airways further when lying down.
The circle closes
Sleep becomes even more restless, and mouth breathing becomes more entrenched.
We do not recommend taping the mouth shut at night; more on this under Mouth taping. If you have breathing pauses, your sleep should be examined by a doctor, and you should not stop a prescribed therapy on your own.
Chewing and microbiome
Digestion begins in the mouth
The last part of the episode deals with a stage that is rarely mentioned when it comes to weight.
With every bite you chew thoroughly, saliva mixes with the food and digestion begins. Only when the bite has been broken down and mixed with saliva does swallowing follow, one of the processes you carry out many hundreds to a thousand times a day. If you eat quickly and chew little, you partly skip this first step.
in a review showed that chewing for longer reduced the amount eaten. The review was produced with the involvement of a chewing gum manufacturer, and the authors themselves consider the data preliminary11
An estimated 38 trillion bacteria live in your body, roughly as many as it has cells of its own. Together they weigh around 200 grams12. This community, the microbiome, is involved in processing food.
The microbiome also appears to store earlier phases. In mice, the gut flora remained altered after a successful diet, and the animals regained weight faster. When this gut flora was transferred to germ-free mice, they too gained weight faster13. This has not yet been demonstrated in humans.
The triad
Two memories: one can be trained
FaceFormer training is not a weight-loss programme. It targets the basic functions of breathing, swallowing and head balance, which in our view precede many processes in the body.
The memory of the fat cell
- Sits as a chemical mark on the genome of the fat cell
- Develops during phases of excess weight
- Cannot yet be specifically erased
- Can be carried along with the cell for years
The memory of the nervous system
- Stores processes such as breathing, swallowing and head balance
- In our view, it usually develops early, for example through dummies, infections or a blocked nose
- Runs without thinking, by day and by night
- Can be reshaped through precise and frequent repetition
Newborns preferentially breathe through the nose; the larynx and soft palate are positioned so that they can drink and breathe at the same time. In the episode, Dr. Berndsen therefore says that mouth breathing is not innate. In our view, it is usually not a family inheritance, but a pattern that becomes ingrained later, and what has been learned can be relearned.
Breathing
Nasal breathing with loosely closed lips. The oral cavity stays sealed, and the air takes the route through the nose, even during sleep.
Swallowing
After chewing, the tongue rests against the palate, in the tongue reference position, and the swallow proceeds in an orderly way.
Head balance
The head balances above the body. In our view, this keeps the throat clear and relieves the neck and trunk.
In the training, you practise these three functions in one sequence. The FaceFormer sits in the oral vestibule, behind the lips and in front of the teeth. You press it with your lips, bite down briefly and swallow, the tongue goes to the palate, and you breathe through your nose.
From about week 6, the breathing exercise is added, with six seconds of breathing in, a pause with biting down and swallowing, and six seconds of breathing out. You extend the breathing pause afterwards week by week in small steps, only as far as feels comfortable. The free FaceFormer app guides you through the basic exercises; you can find all modules on the exercise pages.
We make no promise regarding weight; too many factors are involved for that. The training corrects the basic functions. You can find out how it is structured and how long it takes under Process and duration.
Everyday life
What you can do in everyday life
Eat slowly
Put your cutlery down between bites and chew thoroughly until the bite is mushy. This gives the satiety signal time.
Lips closed, nose open
During the day, pay attention to loosely closed lips and nasal breathing. In our view, what becomes a habit during the day carries over into the night.
Exercise that lasts
Find a form of exercise that is gentle on your joints and that you enjoy. Regularity counts for more than intensity.
Take sleep seriously
Regular bedtimes and a quiet, dark bedroom support the hormones that regulate hunger and satiety.
Patience with your body
The memory of fat cells needs time. Small changes that you maintain count for more than a strict temporary diet.
Questions
Frequently asked
What is the yo-yo effect?
Regaining weight after a diet, often back to the starting weight. Afterwards the body lowers its energy expenditure, the hormones for hunger and satiety shift, and the fat tissue carries traces of the earlier phase.
Do fat cells really have a memory?
In mice, yes. A study by ETH Zurich found epigenetic marks in the fat cells of formerly overweight animals that remained after weight loss and made the animals regain weight faster. In humans, the same study showed altered gene activity in fat tissue two years after stomach surgery. The marks themselves could not yet be measured in human samples.
How long do fat cells remember the old weight?
A period of two years has been measured in humans. The frequently quoted ten years derive from the lifespan of fat cells. Around 10 % of them are renewed each year, so mathematically the whole stock is replaced about once every ten years. Whether the memory lasts that long has not been studied.
Why am I hungrier after a diet than before?
Because the satiety hormone leptin falls along with the fat stores and the hunger hormone ghrelin rises. In a study with 50 people, both were still shifted one year after the diet. This is a reaction of the body, not a lack of willpower.
Can the yo-yo effect be prevented?
According to current knowledge, it cannot be reliably prevented. It is well documented that regular exercise helps with maintaining weight. Add to that sufficient sleep, eating slowly with thorough chewing, and habits you can keep up, instead of a strict temporary diet.
What does nasal breathing have to do with metabolism?
With nasal breathing, nitric oxide from the sinuses reaches the lungs, and in a small measurement the oxygen pressure was higher than with mouth breathing. No study shows that nasal breathing helps with weight loss. In our view it acts via the oxygen supply and calmer sleep, which helps regulate hunger and satiety.
Does FaceFormer training help with weight loss?
The training is not a weight-loss programme, and we make no promise regarding weight. It trains the basic functions of breathing, swallowing and head balance, that is, nasal breathing, an orderly swallowing sequence and a balanced head. In our view these are foundations on which sleep, eating and exercise build.
More articles from the knowledge section
Where to go next
Sources
- Anderson JW, Konz EC, Frederich RC, Wood CL (2001). Long-term weight-loss maintenance: a meta-analysis of US studies. American Journal of Clinical Nutrition 74(5):579-584. PMID 11684524. Source
- Fothergill E, Guo J, Howard L, Kerns JC, Knuth ND, Brychta R, Chen KY, Skarulis MC, Walter M, Walter PJ, Hall KD (2016). Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. Obesity 24(8):1612-1619. PMID 27136388. Source
- Hinte LC, Castellano-Castillo D, Ghosh A, Melrose K, Gasser E, Noé F, Massier L, Dong H, Sun W, Hoffmann A, Wolfrum C, Rydén M, Mejhert N, Blüher M, von Meyenn F (2024). Adipose tissue retains an epigenetic memory of obesity after weight loss. Nature 636(8042):457-465. PMID 39558077. Correction: Nature 643:E24 (2025). Source
- Spalding KL, Arner E, Westermark PO, Bernard S, Buchholz BA, Bergmann O et al. (2008). Dynamics of fat cell turnover in humans. Nature 453(7196):783-787. PMID 18454136. Source
- Considine RV, Sinha MK, Heiman ML et al. (1996). Serum immunoreactive-leptin concentrations in normal-weight and obese humans. New England Journal of Medicine 334(5):292-295. PMID 8532024. Source
- Sumithran P, Prendergast LA, Delbridge E, Purcell K, Shulkes A, Kriketos A, Proietto J (2011). Long-term persistence of hormonal adaptations to weight loss. New England Journal of Medicine 365(17):1597-1604. PMID 22029981. Source
- Kerns JC, Guo J, Fothergill E, Howard L, Knuth ND, Brychta R, Chen KY, Skarulis MC, Walter PJ, Hall KD (2017). Increased Physical Activity Associated with Less Weight Regain Six Years After “The Biggest Loser” Competition. Obesity 25(11):1838-1843. PMID 29086499. Source
- Lundberg JO, Farkas-Szallasi T, Weitzberg E et al. (1995). High nitric oxide production in human paranasal sinuses. Nature Medicine 1(4):370-373. PMID 7585069. Source
- Lundberg JO, Settergren G, Gelinder S, Lundberg JM, Alving K, Weitzberg E (1996). Inhalation of nasally derived nitric oxide modulates pulmonary function in humans. Acta Physiologica Scandinavica 158(4):343-347. PMID 8971255. Source
- Taheri S, Lin L, Austin D, Young T, Mignot E (2004). Short sleep duration is associated with reduced leptin, elevated ghrelin, and increased body mass index. PLoS Medicine 1(3):e62. PMID 15602591. Source
- Miquel-Kergoat S, Azais-Braesco V, Burton-Freeman B, Hetherington MM (2015). Effects of chewing on appetite, food intake and gut hormones: A systematic review and meta-analysis. Physiology & Behavior 151:88-96. PMID 26188140. Source
- Sender R, Fuchs S, Milo R (2016). Revised Estimates for the Number of Human and Bacteria Cells in the Body. PLoS Biology 14(8):e1002533. PMID 27541692. Source
- Thaiss CA, Itav S, Rothschild D et al. (2016). Persistent microbiome alterations modulate the rate of post-dieting weight regain. Nature 540(7634):544-551. PMID 27906159. Source
- Arterburn DE, Telem DA, Kushner RF, Courcoulas AP (2020). Benefits and Risks of Bariatric Surgery in Adults: A Review. JAMA 324(9):879-887. PMID 32870301. Source
- Wilding JPH, Batterham RL, Calanna S, Davies M, Van Gaal LF, Lingvay I et al. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine 384(11):989-1002. PMID 33567185. Source
- Wilding JPH, Batterham RL, Davies M, Van Gaal LF, Kandler K, Konakli K et al. (2022). Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes, Obesity and Metabolism 24(8):1553-1564. PMID 35441470. Source
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FaceFormer training aims to restore the physiological setting of the basic functions of breathing, swallowing and head balance, with lip closure and the tongue reference position, thereby creating the conditions under which symptoms can improve. It does not replace a medical assessment. You can find practitioners near you in the practitioner directory.
