The Dr Louise Newson Podcast - 23 - The truth about GLP-1s, weight loss and nutrition with Dr Jack Mosley

Episode Date: September 2, 2025

GLP-1 medications such as Ozempic, Wegovy and Mounjaro have become some of the most widely discussed weight loss treatments in the world.  They were once mainly talked about in medical research, but now they’re a regular feature in celebrity culture, weight loss headlines and even major advertising campaigns, including one recently fronted by Serena Williams.But beyond the endorsements and headlines, what do we really know about these drugs? How effective are GLP-1 weight loss medications, what risks and side effects should be considered, and how should they fit alongside approaches like nutrition, exercise and hormone balance?In this episode, Dr Louise Newson is joined by Dr Jack Mosley, GP registrar, author and son of the late Dr Michael Mosley. They explore the science, benefits and limitations of GLP-1s, why weight management remains such a challenge, and how lifestyle and medical treatments can complement one another.Jack also reflects on his father’s legacy and offers his own perspective on where medicine is heading. It’s a thoughtful and wide-ranging discussion that brings clarity to one of the most high-profile debates in health today.Don’t forget, the Dr Louise Newson Podcast has been nominated in the British Podcast Awards. You can vote here: https://www.britishpodcastawards.com/votingAvailable to watch on YouTube‍LET'S CONNECT  Website 👉 https://www.drlouisenewson.co.uk/Instagram 👉   / @drlouisenewsonpodcast  LinkedIn 👉     / https://www.linkedin.com/in/drlouisenewson/ TikTok 👉   / https://www.tiktok.com/@drlouisenewson Spotify 👉 https://open.spotify.com/show/7dCctfyI9bODGDaFnjfKhg ‍LEARN MORE Take my online education course, Hormones Unlocked 👉 https://www.learningwithexperts.com/products/hormones-unlocked-dr-louise-newson Sign up for my Confidence in Menopause Course 👉 https://www.drlouisenewson.co.uk/education---confidence-in-menopause

Some of you might know already, but this podcast has been nominated by the British podcast awards for the listeners' choice. So we really need your votes because it would be such an honour and thrill to do well in this. So if you go to the show notes and click on the link, it won't take you long. Please just vote for us. Thank you so much. On my podcast today, I've got Dr Jack Mosley, who's a GP registrar and an author. He's also the son of the late Dr Michael Mosley. We have a conversation about nutrition, about GLP-1s, what they're good at doing and what perhaps they're not so good at doing. And we talk about fat, the role of fat, how it can be detrimental for our future health and also obviously talk about hormones.

So it's a great conversation. I hope you enjoy it. So Jack, great that you're here from Manchester, which makes me feel very nostalgic because I spent many happy year in Manchester. and actually you did some of your GP training where I did my GP training, so small world. Yeah, thank you so much for having me. And like you were saying, we've worked in some of the same hospitals, some of the same GP practices as well. Yeah. Which is very interesting.

But you know, medicine's really changed. So it was 25 years ago that I became a GP. And, you know, we didn't, we had a bit of obesity, but not much. The NHS was not on its knees as it is now. It was, we were really, we've always been really holistic in our care. But now it's just, everyone's shattered. Everyone's, the system's broken. And I was in hospital a year ago when my, my middle daughter fractured her pelvis.

And I was really shocked by not just the patients, really a lot more overweight than patients that I looked after when I was in hospital, but the staff as well, actually. And then it's impossible to get food in a hospital, like impossible to get food. fresh food in hospitality you know so it's the system is set up to fail us in the way when we're thinking about obesity and being overweight it's so easy to put on weight isn't it without a doubt I think we live in this toxic food environment we're surrounded by these processed junk foods wherever we look and these foods are they're designed to be addictive and they're designed to overwhelm our you know, our natural satiety sense and that, you know, sense of fullness.

And like you say, it's actually very relevant for the NHS on so many levels. And not just the patients, but the staff too. So when you go to hospital, a lot of the canteens, they're very beige food. You've got, you know, vending machines all over the hospitals. So especially when people are so stressed, they are not reaching for the broccoli. not reaching for the veg. They are reaching for, you know, those unhealthy snacks, like the Mars bars, the chocolate bars, the crisps. And it's easy to eat badly. You know, I've always looked at my diet, but I wasn't taught much at medical school about nutrition. Most of what I've

done is I've learnt myself. But I had pancreatitis a few years ago and was really ill. And I really, really then looked at my nutrition. Was there anything I could do to help the pain and discomfort I got after and then I have migraine as well so if I ate ready meal it would trigger a migraine so I'm sort of lucky and not lucky that I can't just eat awful food but it is so easy now more than it ever has been but sometimes it's when we have something that happens to us and we realize that we feel so much better eating well then it it spurs you to think about your patience and I know you know your late father Michael was an incredible incredible man educated to like just the way he thought it beyond the box.

But he had an experience, didn't he? Where he changed his nutrition and, you know, looking at type 2 diabetes and trying to prevent disease as well with and treat disease with food, which was a bit out there when he was started to talk about it, wasn't it? Yeah, without a doubt. So he famously was able to reverse his own type 2 diabetes through diet, which the medical establishment at the time, thought you know type 2 diabetes is this chronic condition yeah you just take more and more pills and eventually end up on insulin after around 10 years yeah he was able to lose around 10 kilos uh so a lot of weight yeah no it's a significant amount of weight and a lot of that weight goes you know initially actually off your liver and your your visceral fat um and he was able to lose that weight and

keep it off and stay um in remission of type 2 diabetes and i think think I completely relate to this. Having that own personal experience makes a huge difference. In fact, I've always been quite skinny. I thought I couldn't put on weight. But when I started work as a junior doctor, I managed to put on 15 kilos of weight. Yeah, within the first year of work as a junior doctor. And like I said, it comes back to that.

It's that you're very stressed as you don't know your place in the hospital. I was commuting to work an hour each way. you know, munching on sweets. And yeah, again, eating beige food in the hospital, eating celebrations given by really grateful patients. So, so easy on the walls, isn't it? Exactly, no, without doubt.

So I think it's so easy to put on weight in this day and age. And I think that's a lot to do with the environment, really. That's a lot. I mean, I know you're tall, but that's a lot of weight. And so how did you lose it? I lost it just by making kind of small changes over time. I started cooking some of my own food. I stopped eating sweets on the way to hospital.

And, you know, I think I was lucky that my parents taught me quite a lot about, you know, cooking and eating well and that sort of thing. So I didn't make any drastic changes, but I just, you know, made a few small changes and started, I kind of stopped exercising as well, which I think was adding to my stress. Yeah, it's interesting because obviously your mom's amazing cooking, because she's devised so many recipes and everything else. And it's very easy to look at your mum and dad. You know, your mum's really lean.

She's probably got a very good metabolism as well. But knowing your father in later years, he just looked so healthy and lean. So it's easy to think, oh, he's lucky. But actually, he worked at it and really changed his nutrition, didn't he? He definitely, you know, he was addicted to chocolate and he had a massive sweet tooth. So, and I think that's what made him so relatable because, you know, he was saying, you know, he thought willpower was overrated. And, um, but you had to, his whole idea was really ingraining these, um, healthy habits and making sure that, you know, you set up your own food environment so that you weren't tempted by these foods. Um, you know, he, like I said, he famously ate all our chocolate eggs. This was before.

he changed his ways but he was definitely a chocolate addicts and he just managed to really change his diet and lose his weight and keep it off and I think that's what was so made him so inspiring to people and I do think you know as a doctor and a patient as patients we have to have responsibility for our health we can't just expect people to medicalise us and treat us all the time and I mean I used to have really sweet tooth and I've never been particularly overweight, but I was bigger as a medical student than I am now, and that's probably because I was drinking alcohol, which I don't drink now, and eating rubbish, like you say, on the wards, you're doing on call, like, what else do you do? It's really difficult. So you go to

the vending machine, you get some stuff from the, you know, the nurses station, if it's three in the morning and you just want to keep, keep awake. And then having three children when you're awake, you know, I just didn't look after myself in the same way. But then you start to feel better. And now my blessing and curses migraine because it stops me eating junk food. Yeah, without done. And I have to be really prepared. I always make food and I always have it in a little yogurt pot. So I'm out and about and I've got something there or I've got nuts or whatever as a snack.

But for most people, it's not so easy. And I can see, you know, whenever you go and fill up with petrol, like there's nothing that I would eat in those places or drink, actually, other than maybe some water. But it's impossible often for people to. to access food. So we do have an obesity crisis, don't we? We definitely do. And like you say, well, for you, I mean, you've gone through some horrible experiences

like pancreatitis is extremely nasty. You know, migraines are very, very nasty. To some people can leave you incapacitated for a few days. I think, you know, not everyone even knows how big a role nutrition does play in that, which is interesting as well. And, yeah, the petrol station example is so relatable to everyone because how easy is it to, I mean, how hard is it to go to the petrol station and not pick up that bar of the sweets or the chocolate bar on that long journey?

And I think it's also interesting when you are stressed. So, you know, stress serves a useful evolutionary benefit, especially in the wild because you get that sugar rush and you're prepared for the fight or flight. but when it's chronic, then you have that constant sugar in your bloodstream and the cortisol. It can really lead to these maladaptive eating habits and that. Like what you're alluding to is either vicious cycle or a bit of a virtuous cycle of when you're not feeling well and when you're feeling stressed, you can, you know, you eat rubbish. Then you feel worse and then it gets into this vicious cycle. And it's very hard to get out of it. And I'm very interested in, you know, the role of instance.

with other hormones as well. So cortisol and insulin are very closely together, don't they? And, you know, it's sort of since I qualified, people talk more and more about, you know, the sugar peaks and troughs, the insulin being coming, squeeze out of the pancreas. And that has a real effect on the pancreas. The pancreas gets tired. The system gets tired. You know, this metabolic syndrome that occurs is actually very common.

but also fat cells lots of people think that fat is just a bit of blubber and you've already said something about bisseral fat so the internal fat around our hearts and our digestive system is very different to the fat on our externally sort of on our thighs or bottoms or whatever but fat is metabolically active isn't it yeah so the yeah so you've got those some of the two kind of key fats that we talk about are, yes, visceral fat, which is that nasty, metabolically active fat that clings to your organs and causes, you know, it clogs up your liver, it clogs out your pancreas and can lead to all sorts of health problems like type 2 diabetes, but can also lead to, you know, cardiovascular disease, heart disease, stroke. And then you've got the more, you've got that subcutaneous fat that's under the skin, which is a lot safer type of fat. And actually, that's not, really metabolically active in the same way. And yeah, there's the,

there's a kind of concept of the personal fat threshold where people, beyond a certain weight, you know, that fat kind of starts overspilling. So it goes from the subcutaneous fat and starts clogging up your belly, really. And that's really the dangerous fan. Yeah. And I'm very interested in inflammation.

And we've got lots of cytokines, are chemicals from our fat cells, are adipocytes that get release into the system and increase inflammation in the body even more. So it's important. So it's not just how we look. It's what's going on in our systems. And as doctors, obviously we treat diseases, but we want to prevent diseases as well, don't we? And it's so important. So you've written this book, Food Noise, how weight loss medications and smart nutrition can silence your cravings. And I really like this smart nutrition because like I really enjoy food, but I think the trick is being able to eat and then not feel hungry.

Yeah, without a doubt. It's quite a good hat though, isn't it? Exactly. Yes, I wrote the book Food Noise because I was kind of, I was seeing how the GLP ones were really sweeping the world. There was this fascination about them. And for good reason, because they are very effective at weight loss. but people, you know, people don't, a lot of people don't necessarily understand the risks and rewards, the side effects and how to manage them, and that these are, they're not magic bullets.

These are really powerful drugs. Yeah. So we really need to approach them with kind of care and knowledge, I think. And I think that's crucially important. So when I was at Manchester Royal Infirmary in the 1990s, I was working with an upper GI surgeon. and they started doing gastric bandings which shows how old I am but it was a revolutionary weight loss treatment

and so they would see the patients would see a psychologist beforehand and then they would have this banding and I'm sure you know the first branding operations they were far too tight so literally people could only have a thimble full of food and women would come back to say this is amazing I've lost X number of dress sizes

I'm really slim but then their hair would start to fall out their nails would split they couldn't get any vitamins in And then we realized a lot of people were using things like having things like Quavers crisps and liquidizing them to get them so that they were, you know, really small volumes. So they would still be eating rubbish. But nutritionally, they would not be well at all. And a lot of them then had their branding reversed. So then it made me really think about this relationship with food. It's very different to alcohol and smoking, which are optional.

No one has to drink or smoke. No, exactly. We have to eat. But if you haven't had, you know, you've grown up in a household where food is really important and it's cooked from fresh. But if people haven't, and then a lot of these foods, like you say, they are addictive. We know they're addictive. But they also then people crave it because there's an addiction. So they've got this cycle.

So GLP ones, like you say, do have a role. But they're, and I think in the book you're very clear that they're not really the first go-to. for a lot of people. Yeah. So, and that's why I kind of tried to highlight in the book. I'm not necessarily for or against these medications. But, and they can be really beneficial to certain people who are living with obesity, who living with an obesity related diseases and have tried a lot of these other dietary options.

Because it is like we talked about earlier with the food environment. It is very difficult for some people in this food environment and as well, some, genes also play quite a big role in weight. With regards to, I think the key with these weight loss medications, if you are to do them, is to make sure you are eating this nutritious food. We're overfed, but we're undernourished. So people are really eating these kind of calorie rich,

but nutrient poor foods. So like you say, back in the day, you'd be liquidizing Mars bars, eating quavers. So that can lead to its own form of problems. And they did a study in America that showed half of people living with obesity, have some micronutrient deficiency already. So you could be exacerbating that problem if you don't change your diet and if you don't change your lifestyle.

So I think if you are thinking of taking these weight loss medications, you need to really think about as an opportunity to change those lifestyle behaviours without that pesky food noise. Yeah. And that food not ease is really can take over a lot of people's lives. And what some people who I know who have taken GLP ones are so that they just don't feel hungry and they love it. But then they don't go out to the restaurant.

They don't go to people's for supper or they've had to adjust the amount that they eat. But then they're not enjoying food in the same way. And that can be really restrictive, actually, can't it? Yeah. I think it's a very interesting time that we live in in that, you know already people are probably become a bit more socially isolated i think food is a very binding uh experience you know a lot of our socializing does revolve around food so once you remove that then that could be an issue and especially um yeah people may not be going out for dinner

they may not be doing dinner parties in the same way that sort of thing or even having a kind of family dinner um in the conventional way so so there are you know this is going to have a massive impact on the whole of society I think yeah and so with with sugar cravings and food cravings I see it a lot in women obviously I see a lot of women in the clinic and we see a lot of menopoles are women perimenopals are women but also a lot of women with premenstrual syndrome PMS and premenstrual dysphoric disorder PMDD and I used to get it before I had my periods those few days before you're just like oh I just want to eat chocolate I just want to eat a real carb craving. And I thought, oh, maybe it's just in my head, but then my peer would come and I'd

feel fine, and I wouldn't make, wouldn't need that in the same way. But we know that these hormones, estrogen, progesterone and testosterone actually have really important cardiometabolic functions. And so insulin can be really altered when we don't have esterdal and progesterone in our bodies. So a lot of women that we see, when we balance their hormones, their metabolism can change, their cravings can reduce, but also their ability to just function. You know, their brain comes back, but also their bodies as well, they're more likely to exercise, more likely to have the motivation to cook. And I feel it's a shame if they're going to, like the GLP ones before having their hormones balanced. Yeah. I mean, it's really,

really important because like you say, that period around perimenopause and menopause, your hormones completely change. And the decline in the, the decline in, you know, it's really important. And the, in estrogen and testosterone and progesterone, they can have big effects on you. Especially changing in body composition. So we kind of talked about that visceral fat and the subcutaneous fat. A lot before menopause, a lot of it, that fat is more stored in subcutaneous, but it can kind of navigate to visceral fat between menopause. Also, things like muscle loss can accelerate at menopause.

And other things like, osteoporosis. So that's where there, you know, these GLP ones, there are some beneficial effects potentially if people are able to lose weight on them. But then you also have these other factors. Like we know one of the risks of GLP ones is that a significant amount of the weight you lose is muscle or lean body mass. And I do also have some concerns for it could, in certain people who aren't eating the right nutrition, it could actually potentially exacerbate things like osteoporosis, especially, I think, in menopausal women.

And that's a real concern because we know osteoporosis is really common. Some people quote one in two menopausal women, and certainly one of the reasons I take hormones is to protect my bones and try and keep them strong. But osteosarcopenia, long word, but bone loss and muscle loss, as we don't have hormones, is really, really common. and it's sort of been ignored for a long time,

you know, frail old ladies with their zimaphraines, but actually they've lost their muscles, they've lost bone density, they've lost their hormones. So thinking about preventative medicine, giving hormones will help their muscles, it will help their bones. But with the gLP ones, if they're losing bone density,

they're losing muscle and their menopausal, it's like a double whammy, isn't it? It can be. Yeah, and I think, there are yeah there are exactly there are definitely risks there and um you know we know from the studies that 25 to 40 percent of the uh the weight you lose is is lean body mass and a main component of that is muscle um and you know muscle is so important for longevity but also um you know living healthy um independent life in later age so kind of living happy and independent

which is just obviously so important to so many people. But also muscle is metabolically active. We've talked about fat cells being metabolically active in a negative way. But muscle is actually very metabolically active in a positive way. So people who have more lean muscle, their metabolism is going to be different actually. And muscle can produce lots of hormones as well and very anti-inflammatory substances. So people might look the same externally. But their body composition and we have a depth.

a scan in the clinic and you can see the difference internally. So where that visceral fat is, where their muscles are. It's really important, isn't it? Yeah, no, it really is. And I think that the body, yeah, body composition, I mean, there are limits to BMI, which is a kind of normal assessment of who is health, described as healthy, overweight, living with obesity. But that body composition is so important because some people,

unfortunately, do have more visceral fat than others. some people like you say have more muscle than others and during that perimenopause and menopausal period um so from the age of around from the age of uh your early 30s you start to lose 5% of your body weight um every decade so 5% of your muscle mass every decade and that can really accelerate from 60s onwards so you have all these compounding factors so that's why i think it's so important to consider um you know so firstly you know eating yeah eating enough protein because your your appetite is really restricted if you are taking these glp1 weight loss medications so getting enough protein is is important but also these other things are good for bone health like you know calcium

magnesium and vitamin d is really important um and then thinking about doing some strength training actually is is very important for some some people and uh weight bearing exercises that can um so weight bearing exercise what i mean by that is kind of yeah obviously uh you know things like dancing running racket sports all of these things that put pressure healthy pressure on your on your bones and can help really with things like osteoporosis yeah it's really important um my my husband's a surgeon and sometimes he sees people with a bMI body mass index of 50 like they're morbidly obese and they need surgery and glp1s certainly

certainly have a role there. But when he talks to them, they're like, yeah, there's no way I can change my diet. Yeah, there's no way I'll exercise. And they just think this is going to be a magic drug, which, yes, it could be, but it's not helping internally. And I think looking at the nutritional status of our patients is crucially important, isn't it? So I was talking to someone last night who he wouldn't look at him and say he's overweight at all.

He'd drunk a bottle of wine as he came home. and sort of eats maybe a little bit more than he should. And he said, you know what, I think I might just take a JLP one. I'm just going to have a microdose and just see how that goes. And I just told him that he was really stupid. And he said, but everyone's doing it. And he's not medical. He's just been reading stuff about it.

But I see quite a lot of patients. I don't prescribe JLP once, and we don't prescribe a clinic. But they're sort of my shape, but they want to get in their bikini for the summer. And doctors giving them GLP ones without any nutrition advice, without looking at their exercise, without thinking about cutting down their alcohol maybe. I just feel about uncomfortable with that. I don't know what you think. And that's why I kind of wrote this book at the end of the day. It's the wild west out there of online pharmacies.

You know, people are not provided that much information about these medications. They're not provided that much advice about nutrition and lifestyle strategies. So these medications, they're not a cosmetic drug and they're not a medication to get, you know, lose a few kilos for the wedding or get beach body ready. These are powerful drugs which have some potential downstream consequences, especially for people who are described as a kind of healthy BMI. And especially for people who don't change their diet while they're on them,

I think that is so crucial to have the right nutritional strategies. in place. I think this is where your book does come into play really well because you know you've got some even lovely pictures as well and you know how we can still eat and they're not particularly difficult things to cook are they and you know they're not like got loads and loads of ingredients but there's nice colour there's going to be vitamins in these and nutrients which is really important because a lot of people when they lose their appetite will just have little snacks of things that like you say, their nutritional status probably be worse than it was before they started these drugs sometimes. So what you're really saying is if you are going to take them,

it has to be done in conjunction. Well, I would say with hormones if they need hormones, but that's fine. You agree with that. But looking at nutrition as well, it's crucially important, isn't it? Like you, I would say, yeah, I'm a kind of, you know, diet first approach, because I think that is clearly very, very important. And there are kind of several ways of doing that I kind of discuss in the book. But like I say, for some people who who have really struggled with their weight, they can be beneficial. But I just think you do need that right dietary approach.

And yeah, like you say, I think there's lots of other factors involved in weight, in weight gain, and hormones are clearly a massive factor in that. And for men as well, you know, there's quite a lot of people who are younger as well that have low testosterone and they've got into this cycle. And in fact, I saw a lady in my clinic on Monday who'd had really bad PMDD, premenciled disorder. And she had no hormones. And I'd given her some hormones.

She also had some endometriosis as well and a lot of urinary tract infections. So I'd given her some hormones and her testosterone level was really, really low as well. So she had that and she felt amazing. And then she's lost seven kilograms in weight. And she's just changed her whole. She's only 22, but she changed her whole diet. She's been on the contraceptive pill for six, seven years. She's off that, obviously.

She changed her exeter, change her nutrition. And I did her hormone blood test, and they were on the high side. And she's on a really low dose of hormones. I said, you know what? I think your ovaries have just started working again. So she's stopped her hormones, but she's got this new lifestyle. And, you know, you see that in men as well who take testosterone sometimes. Yeah, yeah.

Taking that testosterone means that they're metabolically, things are changing and improving. Then they exercise more, they lose weight, their whole lifestyle changes. And then they don't need testosterone forever. But I think it's looking at everything in conjunction. And that doesn't always happen in medicine because it's very siloed, isn't it? No, exactly. Yeah, that's what we were kind of, yeah, talking about before this started really, how unfortunately a lot of medicine is quite siloed.

there's not anywhere near enough nutritional teaching at medical school and all the way along. I think it is so important, you know, to look at clearly, yeah, clearly modern medicine has made massive impacts for the goods to people's lives, but I think the nutritional and lifestyle side of things is somewhat ignored, really. And I think it's, people are kind of starting to understand that a little bit more over the last decade, only really over the last decade, I would say. Yeah, it's taking a while. So it's great.

I've really enjoyed this conversation, but I always leave with three take-home tips. So you're sort of at the beginning of your career in some ways as GP, writer, educator. What three things do you think your work is going to make the biggest impact on over the next decade? What three, sorry, what three areas? Yeah, what things in 10 years time? What three things do you think that you will make a difference to as many people as possible? Because clearly you're doing great educating. Yeah.

But what would you like to see change to improve the health of people? What I would like to see. I think firstly, we talked about this kind of toxic food environment. I think you do need some more, something does need to change with, you know, putting some regulations and making some changes to how we, you know, advertising of these highly processed junk foods and some of the taxation of these foods, I think that could make a big difference. Secondly, I would say I'm so passionate about nutrition and teaching, you know, what makes a healthy diet. And I think that is so vital, you know, for everyone, but actually, I think especially for clinicians who are seeing people in

in primary care in hospitals, being able to be armed with up-to-date, up-to-date understanding of how these things work is so important. And I think thirdly, these GLP ones, they're not a passing fact. They're not going away anytime soon. So I think we need the right advice and the right information out there with how to deal with them and how to use them safely and effectively. Like I say, they're not for everyone, but for some people they can be beneficial.

But I think you still need the right nutritional and lifestyle strategies alongside it. Absolutely. So if you are thinking of taking them, don't just do it on your own, make sure you get really good advice. Exactly, yeah. So thank you so much.

I've really enjoyed it. Thank you. Yeah, no, thank you so much for having me. It's been great, yeah. Thanks.