This is the complete English translation of the edited conversation. The original podcast and video are in German.
Fat loss over forty, strength training, peptides and GLP-1: a conversation with Mike Steiner, also known as Iron Mike.
Mike Steiner on belly fat and biohacking
Mike Steiner on belly fat, metabolism and biohacking: In this conversation with Reza Mehman, we explore why fat loss often seems harder as we get older and the roles of training, everyday movement and muscle mass. He explains his view of metabolism between the ages of twenty and sixty, and why less movement, more stress and changing habits often coincide with weight gain. We then discuss belly fat, HYROX, strength training and maintaining muscle during a diet. In the second part, Mike explains what biohacking means to him and why he studies peptides and new compounds so intensively. GLP-1 receptor agonists and retatrutide feature prominently as he discusses common claims and current research from his perspective. Finally, he talks about health myths on social media and his ambition to make complex research understandable to a wider audience.
Summary
One-sentence version: Mike Steiner explains why belly fat is not necessarily just about age, and discusses strength training, everyday movement, biohacking, peptides and GLP-1.
Three-sentence version: Mike Steiner argues that energy expenditure changes less between twenty and sixty than many people assume, while movement, muscle mass, stress and daily life have a major influence. For fat loss, he generally recommends a calorie deficit combined with targeted strength training to better preserve muscle. In the second part, he describes his approach to biohacking and discusses peptides, GLP-1 receptor agonists and retatrutide in detail.
Five-sentence version: Reza Mehman asks Mike Steiner why, despite HYROX training and weight loss, he remains dissatisfied with the results around his stomach. Mike attributes this primarily to changes in movement, muscle mass, stress and lifestyle, rather than a metabolism that has slowed sharply with age. He emphasises strength training and NEAT, or everyday movement outside exercise sessions. He then describes biohacking as an attempt to influence one’s biology through habits, training, nutrition, tools and sometimes medical compounds. Peptides and GLP-1 receptor agonists are a particular focus, discussed through Mike’s interpretation of current research.
Context: who is speaking, what is discussed and why it matters
Who is speaking: Reza Mehman talks with Mike Steiner, who describes himself as a biohacker and studies training, nutrition, longevity, peptides and current research intensively.
What it is about: Belly fat, metabolism, strength training, HYROX, everyday movement, fat loss, biohacking, peptides and GLP-1 receptor agonists.
Why it matters: Many people automatically associate weight gain after forty with a slower metabolism. This conversation challenges that simplified explanation and connects familiar training and nutrition questions with current biohacking and medication topics.
Three central questions:
- Why does belly fat often remain particularly stubborn despite exercise and weight loss?
- What roles do strength training, muscle mass and everyday movement play in fat loss?
- How does Mike assess peptides and GLP-1 receptor agonists in relation to biohacking and health?
Contents
- Introduction: an overview of belly fat, metabolism and biohacking
- Summary: the conversation in one, three and five statements
- Context: speakers, subject and relevance
- Themes and context: the main topics
- Key takeaways: the central positions expressed
- Frequently asked questions: belly fat, metabolism and biohacking
- Selected quotes: memorable statements
- The full conversation: the complete edited transcript
- Keywords: relevant search terms
- Names and terms: people and technical vocabulary
- Passage for quotation: a concise reference passage
- Social media snippets: YouTube, LinkedIn and newsletter
- Continue exploring: the podcast and original video
Themes and context
Belly fat and metabolism after forty
Mike challenges the simple explanation that metabolism automatically drops sharply after forty. Instead, he emphasises changes in movement, stress, sleep, hormones and muscle mass.
Tags: belly fat over forty, metabolism after forty, fat loss
Strength training, muscle mass and NEAT
When discussing fat loss, Mike highlights targeted strength training and everyday movement. Preserving muscle should prevent unnecessary loss of lean mass while losing weight.
Tags: strength training, muscle growth, NEAT
Biohacking and peptides
Mike describes biohacking as deliberately modulating one’s biology through lifestyle, training, nutrition, tools and sometimes medical compounds. He sees peptides as a particularly dynamic research field.
Tags: biohacking, peptides, longevity
GLP-1 and retatrutide
Mike offers his perspective on GLP-1 receptor agonists and retatrutide, discussing benefits, side effects, muscle loss, bones and metabolic health.
Tags: GLP-1, retatrutide, weight-loss injections
Health myths on social media
Towards the end, Mike criticises sweeping statements about foods, sweeteners and medication, advocating a closer look at mechanisms and data.
Tags: health myths, social media, science
Key takeaways
- Mike argues that metabolism declines less between twenty and sixty than many people assume.
- Less everyday movement, more stress, less sleep and changes in muscle mass can reinforce the impression of a “slower metabolism”.
- He identifies a calorie deficit and targeted strength training as central factors in fat loss.
- NEAT describes the energy used through movement outside formal exercise.
- In his view, Reza could have included more hypertrophy-focused strength training in his HYROX preparation to preserve muscle better.
- Mike defines biohacking as deliberately influencing biological processes through lifestyle, training, nutrition and other tools.
- He describes peptides as a rapidly growing field in drug development.
- Mike generally views GLP-1 receptor agonists positively when training, nutrition and medical supervision are considered alongside them.
- He highlights retatrutide as a particularly interesting new drug candidate.
- Mike sees education about data and studies as a counterweight to oversimplified health myths on social media.
Frequently asked questions
Why is belly fat often slower to disappear?
Mike attributes Reza’s situation mainly to his training structure, muscle loss and the relatively short period of fat loss so far. He generally recommends a calorie deficit combined with targeted strength training.
Does metabolism automatically slow after forty?
Mike argues that energy expenditure changes much less between twenty and sixty than many people think. Instead, he points to movement, sleep, stress, hormones and lifestyle.
What does NEAT mean?
NEAT stands for non-exercise activity thermogenesis. It means the energy used through everyday movement outside formal exercise, such as walking, climbing stairs or unconscious movement.
Why is strength training important during weight loss?
Mike explains that strength training can help preserve muscle during weight loss, so more of the weight lost comes from fat rather than muscle.
What does biohacking mean to Mike Steiner?
He describes biohacking as an attempt to deliberately modulate one’s biology. He includes habits, training, nutrition, tools and sometimes off-label medicines or experimental peptides.
What are peptides?
Mike describes peptides as chains of amino acids that can perform different functions in the body depending on their composition. He sees them as a rapidly growing field in pharmaceutical research.
How does Mike assess GLP-1 receptor agonists?
Mike views GLP-1 receptor agonists much more positively than many public debates suggest. His statements reflect his interpretation of the research and are linked to lifestyle, strength training, nutrition and medical supervision.
What is retatrutide?
In the conversation, retatrutide is described as a new drug candidate that targets the glucagon receptor alongside GLP-1 and other signalling pathways. Mike discusses possible effects on appetite, energy expenditure and liver fat in particular.
What does Mike criticise about health content on social media?
He criticises blanket warnings about foods, sweeteners and medicines when he believes the data does not sufficiently support them. He aims to explain mechanisms and research with greater nuance.
Selected quotes
“Correlation does not equal causation is a very important statement in science.” — Mike Steiner
“But metabolism itself does not change.” — Mike Steiner
“It takes strength training and an established routine.” — Mike Steiner
“Peptides are the new hope for medicines.” — Mike Steiner
“The unhealthiest thing we have today is obesity.” — Mike Steiner
“That is why it is important to take on a small educational role today.” — Mike Steiner
The full conversation
Strength training, cardio and longevity
Reza Mehman:
So you do a little exercise, then.
Mike Steiner:
It is funny, but I would not really even call strength training a sport when it is done specifically to produce the greatest benefit for muscle.
Reza Mehman:
Okay.
Mike Steiner:
It is one of the most important longevity interventions we have, and that is now well established. Strength training definitely matters, but the cardio component needs to be added separately to cover the other area too. There is more than enough data on that as well. I have just completed the entire longevity module for my new project, my Biohacking Masterclass. It involved an incredible amount of research. Fortunately, I also know a few researchers.
Reza Mehman:
I have to say, and I am not just flattering you, that you are an incredibly smart guy. I follow you on Instagram and YouTube and listen to what you say. You go into such depth, almost down to the molecular level of what happens. It is mind-blowing to me. You do not just flex your muscles; you have the expertise behind it.
Why belly fat can remain despite training
Reza Mehman:
But selfishly returning to my problem: what do I actually need to do, and why am I losing weight everywhere except my stomach? What is the particular problem with belly fat?
What metabolism actually means
Mike Steiner:
First, a few basics, because there is this common view: “I am forty, and my belly is getting bigger.” We have relatively recent meta-analyses on metabolism. I will use that term, although I do not really like it. It always sounds like something we cannot influence, which simply is not true. Metabolism between twenty and sixty—does it change?
Reza Mehman:
What is metabolism? Let us start there.
Mike Steiner:
Metabolism means energy turnover, mainly at rest, but also the translation of what we do, including sporting performance, into calories burned as fuel. We burn fat and calories. Who here thinks metabolism gets weaker or declines between twenty and sixty? Hands up. Who thinks the opposite?
Reza Mehman:
Mrs Kleinemeier, really? Now I am curious. I did not quite see everyone. Who thinks it declines? Hands up again. Who thinks it stays the same? Fewer people.
Does metabolism change between twenty and sixty?
Mike Steiner:
It does not change at all, actually. That is what the meta-analyses and long-term evaluations consistently show. Metabolism is very well researched; few things have been studied so thoroughly. “Correlation does not equal causation” is a very important statement in science. Here we are talking about correlation—things occurring together. Take you, or anyone else. When we were young, we did lots of sport and played football. It happened almost incidentally. We were out and about and rode bicycles. Then we became more successful at work, had children, went out less, did less, slept less and experienced more stress. Cortisol rises, hormones decline, and ageing also lowers some hormones. All of that correlates, but metabolism itself does not change.
When you bring your movement back to a level that reduces your calorie surplus and puts you into a deficit, you will burn fat again. It is that simple. The most important factor in avoiding becoming “skinny fat”, to use that expression—which is what you are worried about—is a proper balance. “Skinny fat” sounds good, does it not? I recently made a YouTube video about it because it remains a very active topic surrounded by myths.
NEAT, everyday movement and calorie expenditure
Mike Steiner:
It takes strength training and an established routine. NEAT—non-exercise activity thermogenesis—is actually the most important factor. It includes all movement outside training, even something like this. People who cannot sit still have much higher NEAT than others. It includes kissing your partner, writing, and deciding whether to take the stairs or the lift. The idea of people having a better or worse metabolism applies only to a limited extent. I have also studied thyroid issues in depth. For years, I have worked with private doctors on different hormone therapies. The thyroid is fascinating because metabolic rates do fluctuate between an overactive and an underactive thyroid.
But even those differences are not as large as people often like to believe.
Reza Mehman:
Okay.
Why Reza is not losing belly fat faster
Reza Mehman:
Interesting, but I still do not understand why I am not losing fat specifically around my stomach. I am a little unhappy with that. What can I do about this fat here?
Mike Steiner:
How long did you train for HYROX?
Reza Mehman:
Six or seven months, perhaps. It was not a short time.
Mike Steiner:
What did your strength training look like?
Reza Mehman:
Very specific to HYROX.
Mike Steiner:
So more cardio-focused?
Reza Mehman:
Yes, muscular endurance, I would say.
Mike Steiner:
How long did it take you to gain that belly fat?
Reza Mehman:
Okay, that took a while.
Mike Steiner:
How long do you think?
Reza Mehman:
I would say twenty-two or twenty-three was my prime. Unfortunately, things went downhill afterwards. It took a few years; I agree with you there.
Mike Steiner:
Of course, it would be a nightmare if losing it took just as long. That is not the case; fat can be burned relatively quickly. But we still need to remember that it takes an investment of time. First, I think you gave it slightly too little time.
Strength training, muscle retention and fat loss
Mike Steiner:
Second, more specific hypertrophy-focused strength training should have balanced the endurance work, maintaining the muscle-preserving effect so you lost fat more specifically rather than total mass. You lost a lot of body mass, much of it fat, but some muscle too. As you noticed, with less muscle your baseline energy expenditure gradually declined. That is essentially the explanation. You have probably accumulated quite a lot of visceral fat in that area. That is also a treatment area we work with, and it can be targeted, so to speak, but it does not have to be.
You can simply work with a calorie deficit and strength training, and then lose it.
Biohacking and useful interventions
Reza Mehman:
That is possible, but you are also a biohacker. By the way, who here knows Mike? I do not know whether this is the right audience, but I would be interested to know who follows him on social media. Yes, please follow him! Stefan, really? Sebastian, you raised your hand too. There were a few over here: Freddy, Ivo, Sire, Asma at the back, and Dominik here. That is quite a few people. That is lovely; I am really pleased. You have several hundred thousand followers, of course. And you can probably tell he knows what he is talking about.
If I asked you as a biohacker for tips on performing well in everyday life as someone over forty with the issues I have, what would you recommend? Peptides are on everyone’s lips at the moment too. I am trying to fit in as many topics as possible. Would you say, “Reza, you can take this peptide to improve performance,” or, “Forget all that, eat healthily and sleep more”? What advice would you give me?
What Mike means by biohacking
Mike Steiner:
It is important to understand the approach behind what I do. I was the first to define myself as a biohacker in Germany; the term did not really exist here before. Many people in the US and overseas do it. They try to modulate their biology so their bodies function better in some way, mainly through habits, training, nutrition and various tools. But that can also include off-label medicines, for which there is a lot of research, and experimental peptides—medicines on the path towards approval. Many people probably do not know that a large proportion of today’s medicines are already peptides. The peptide market, its pharmaceutical segment, is growing ten times faster than the others.
Can you call it a pharmaceutical segment?
Reza Mehman:
Could you explain peptides again?
What peptides are and why they interest him
Mike Steiner:
I will start by saying that peptides are the new hope for medicines because they do not act as aggressively as the medicines we currently use as tools. Fundamentally, they are chains of amino acids joined together. There is an amino acid, bonds hold them together, and we have a peptide. Creatine is a peptide, a tripeptide made from three amino acids. Depending on the arrangement of those amino acids, peptides can perform different tasks in the body—and do perform them. All peptides are endogenous: we have peptides in our bodies, carrying out these tasks every day.
The classic difference from medicines we normally take, some of which we can simply buy at a pharmacy, is this: a medicine enters your body, sees something is not working and hits it with a hammer, regardless of what happens afterwards.
Reza Mehman:
So you get liver toxicity, kidney toxicity or whatever else. If I do not know what is wrong, I take paracetamol or ibuprofen, and they hit everything.
Mike Steiner’s perspective on active compounds
Mike Steiner:
Exactly. Ibuprofen also has an interesting cumulative toxicity burden on the kidneys across a lifetime, yet it is freely sold. Peptides, on the other hand, come in and ask who needs help. “Okay, I will help, and when I leave, that system can keep working.” That differs from steroids such as cortisone or testosterone, where the balance can remain more difficult after they leave the body. I think that is the greatest potential of peptides, and why the pharmaceutical market is so interested. Peptides are at different stages of approval in different countries.
Here, hardly any of the commonly discussed ones are approved. Other countries are very different. My work mainly involves helping entrepreneurs or people who want to improve their performance or health find their way through this jungle, based on the current evidence.
Discussing research and approval
For me, biohacking does not stop at a national border. Germany might say, “That is a poison,” while thirty-five other countries say it is an approved medicine that saves lives, with meta-analyses covering more than eleven thousand patients. I do not dismiss that with the arrogance you sometimes encounter here. I look worldwide, especially at the research consensus. Part of my role is to understand how research into different peptides develops, recognise the mechanisms and make predictions about whether they will work in humans in the same way, even if studies have not yet demonstrated it.
For that, I work with drug researchers and a team of doctors. We have now founded a research institute and will be researching peptides.
Which peptides Mike considers relevant
Reza Mehman:
Great, but are there specific ones where you would say, “Take these two or three and everything will be fine”? I need that hack.
Mike Steiner:
It always depends on the context, which nobody wants to hear. But there are two or three peptides that will probably improve your health overall.
GLP-1 receptor agonists and common myths
Mike Steiner:
The first category is GLP-1 receptor agonists—the weight-loss injections. I know there are enormous numbers of myths about them. I am in contact with GLP-1 researchers too, and almost everything you hear out there is wrong. It cannot be explained by the research. They do not break down muscle; dieting does that, which is why you should exercise, specifically strength training. Nor do they make your face hollow; dieting does that too, and it happens with any diet that is too rapid. As for bone loss, comparisons of osteoblasts and osteoclasts in different meta-analyses and studies were fairly balanced between bone-building and bone-breaking processes.
Carcinomas? No cancer—no study has ever shown that. There is a rat study involving thyroid carcinoma, but rats have GLP-1 receptors on certain C cells that we do not, so it does not transfer to us. To explain briefly, that is another thing I do a lot: compare what can and cannot be extrapolated, because otherwise nobody does it. That is essentially how I became known. I speak fairly openly about different compounds because, to me, they do not suddenly become poison because of some arbitrary border. My assessment of each compound draws on its mechanisms, data and anecdotal evidence from coaching or my own experience. I test many things on myself.
Retatrutide and the additional glucagon receptor
Mike Steiner:
Then I make a judgement. Among GLP-1 receptor agonists, there is a very new candidate that will be approved in 2027. Phase three clinical trials—the final relevant phase before approval—are currently producing groundbreaking results. It is called retatrutide. It also targets the glucagon receptor, which means you burn calories too.
Reza Mehman:
I watched your episode about that.
Mike Steiner:
That one really took off too. Retatrutide is sensational because you are not only less hungry; you also burn calories. The mechanism is even more interesting: because it involves the glucagon receptor, the liver metabolises fat. You burn calories from liver fat. In a sub-analysis of phase two trials, patients with diabetes and fatty liver experienced an 89 per cent remission rate. Until then, fatty-liver remission had not even been possible through medication, and retatrutide achieved it almost incidentally.
Obesity, visceral fat and weighing benefits against risks
Mike Steiner:
So when someone asks me whether they can take it, I say that the unhealthiest thing we have today is obesity. That has nothing to do with body shaming; it is a scientific and medical fact. It is associated with almost every type of cancer. Visceral fat is inflammatory tissue, and there is mechanical strain on joints and countless other problems. There is simply no comparison. If someone who is overweight tells me weight-loss injections are unhealthy, that comparison does not even exist; it should not be made.
Lifestyle, strength training and medical supervision
Mike Steiner:
The benefit is so great, and the side-effect profile is now so well researched, that for most people I would say yes—if, and this is crucial, their lifestyle is adapted alongside it. Strength training, healthy food, optimised micronutrients and protein need to be included. You probably need a coach, or at least have to study the subject yourself. The internet is vast. You are also welcome to take my Biohacking Masterclass, which launched successfully a while ago. It is a comprehensive system with more than three hundred videos. We have integrated the Doctrinus medical group, who offer consultations within it. So you can access medical consultations there as well.
Reza Mehman:
Promise me I will look like you at the end.
Mike Steiner:
Actually, yes. We have an Essentials section in the masterclass that is more up to date than any trainer qualification. That section is almost a bonus. You learn everything about training, nutrition and supplements, and we clear up all the myths. It is easy to follow, with videos, PDFs, learning material and quizzes. You learn almost playfully, or simply look up information whenever you want.
The Biohacking Masterclass and education
Mike Steiner:
It is well put together. Unfortunately, I think there are too many misunderstandings in many areas. It is not just about peptides or medicines. It starts with visceral fat, losing belly fat and all kinds of other things. Today, a very problematic countermovement has also developed on social media.
Social media, health myths and countermovements
Mike Steiner:
They have sent me legal warnings several times and given me strikes on YouTube. They try to exploit people’s lack of knowledge and dissatisfaction by telling them certain foods or sweeteners are unhealthy. People who do not know the evidence can quickly fall for many such claims, which actually make them less healthy. That is why it is important to take on a small educational role today. I find it funny that many people in Germany see me as controversial. What I do is not particularly innovative; everyone does it in the US. I am new here, so people say, “Oh my God, he did not just say that!”
But I can back it up with experts from around the world who appear on the Andrew Huberman podcast and discuss it openly. I am simply one of the first to do it here. That is the difference.
Closing thanks
Reza Mehman:
Thank you for your time. You are staying for dinner as well. One special detail: Mike’s mum is here today too. Thank you for joining us; it is a great honour. You can certainly be very proud. Mike, thank you very much.
SEO keywords
Tags: Mike Steiner, biohacking, belly fat, metabolism, strength training, HYROX, fat loss, NEAT, peptides, GLP-1, retatrutide, visceral fat, longevity, muscle mass, nutrition, Reza Mehman Podcast
Names and terms
Mike Steiner, Reza Mehman, HYROX, metabolism, energy turnover, calorie deficit, muscle mass, hypertrophy, strength training, cardio, longevity, NEAT, non-exercise activity thermogenesis, thyroid, visceral fat, biohacking, peptides, amino acids, creatine, off-label medicines, GLP-1, GLP-1 receptor agonists, retatrutide, glucagon receptor, fatty liver, obesity, osteoblasts, osteoclasts, C cells, micronutrients, protein, social media, Andrew Huberman, Biohacking Masterclass.
Passage for quotation
In this conversation, Mike Steiner challenges the simplified idea that a slower metabolism after forty is automatically responsible for more belly fat.
Instead, he emphasises movement, muscle mass, sleep, stress and everyday activity.
He identifies a calorie deficit and targeted strength training as central factors in fat loss.
In the second part, he describes biohacking as deliberately modulating biological processes and discusses peptides and GLP-1 receptor agonists through his interpretation of current research.
His broader aim is to question common health myths more closely through mechanisms and data.
Social media snippets
Why is belly fat the thing that stays, even when you exercise and lose weight?
I discuss this with Mike Steiner. We explore whether metabolism really slows after forty, the roles of muscle mass and everyday movement, and why HYROX training alone is not automatically the best strategy for maximum fat loss.
In the second part, we discuss biohacking, peptides, GLP-1 receptor agonists and retatrutide. Mike explains why he is critical of many public debates about these compounds and how he evaluates research, mechanisms and practical experience together.
Episode timestamps
Timestamps:
00:04 Strength training, cardio and longevity
01:08 Why am I not losing belly fat?
01:21 Metabolism after forty
02:36 Does metabolism change between twenty and sixty?
03:51 NEAT and everyday movement
04:43 Why belly fat seems stubborn
05:47 Strength training and muscle retention
06:33 Biohacking and performance
07:41 What Mike means by biohacking
08:30 What are peptides?
11:08 Which peptides are interesting?
11:25 GLP-1 receptor agonists
12:51 Retatrutide
13:50 Obesity and visceral fat
14:22 Lifestyle and medical supervision
15:31 Health myths on social media
16:48 Closing thoughts
Podcast: Reza Mehman Podcast
Website: Reza Mehman
Instagram: Reza Mehman on Instagram
#Biohacking #BellyFat #Metabolism #StrengthTraining #GLP1 #Peptides #Retatrutide #Longevity #Podcast
Does metabolism really slow after forty?
I discussed this with Mike Steiner.
Four points from our conversation:
* More belly fat is not automatically just a matter of age.
* Muscle mass and everyday movement play an important role in energy expenditure.
* People who want to lose fat should not replace strength training with endurance exercise alone.
* Mike discusses peptides and GLP-1 in a more nuanced way than many social media debates about biohacking.
I was particularly interested in how much of what we perceive as a “bad metabolism” actually comes from changed habits.
The full conversation is available in the podcast and on the blog.
More reflections from episode 192
#Biohacking #Metabolism #StrengthTraining #Health #Longevity
Why does belly fat often remain particularly stubborn even as weight falls? In my conversation with Mike Steiner, we discuss metabolism, muscle mass, strength training, NEAT and what actually changes after forty. In the second part, we explore biohacking, peptides, GLP-1 receptor agonists and retatrutide. Mike discusses common claims from his perspective on current research.
Continue exploring
Find more conversations on the Reza Mehman Podcast page. Watch episode 192 directly on YouTube.
