Dr Jack Mosley

0:04Hello and welcome back to The Midpoint. Today I'm very excited and delighted to have Dr Jack Moseley in the studio. Jack has been a GP for seven years, but it looks like his area of interest and expertise is going to continue to build on the brilliant work done by his late father, Dr Michael Moseley, who many of us know as someone whose affable and easygoing broadcasting style could also be termed as practising what he preached. Of course, his 5-2 diet, where you fast for two days a week on just 800 calories and eat normally for the other five days, was a huge hit. Many people attributed enormous weight loss to it and their long-term management also, and still follow his plan today.

0:44His son Jack has become an expert on GLP-1s and their long-term effects on our health, but he's picking up on his late father's work with his latest project, the Fast 800. So we're going to discuss that, all things fasting, and what he's learned about GLP-1s. Dr Jack Moseley, welcome to The Midpoint. Yeah, thank you so much for having me, Gabby. I'm really looking forward to this today. Well, I've, in your introduction, said that you seem to be developing, after seven or eight years as a GP, you seem to be developing a real interest in some of the areas that we are kind of known your family for, really, and your dad in terms of fasting and now GLP1s have become such a huge topic that you have found yourself getting very interested in them and their effects on people, not just while they're taking them, but afterwards as well.

1:34So can we just go back and kind of work out, is this interest, you think, familial? It comes from your background at home? Or is this something that you as an academic, as a doctor, have found interesting? Well, like you say, I've been working as a doctor for around eight years now, but I do have a long background with my interest in this area. This lifestyle medicine, it was really in its infancy when my dad really started developing a passion for this area. And especially it was really in 2012 when he lost around nine to 10 kilos in weight following the 5-2 diet, where he really developed such a passion.

2:13Did he know about fasting before he started? Like, how did he kind of work out that was the way he was going to lose weight. Where did that come from? Do you remember conversations around the family dinner table about this? Like, why is dad not eating tonight? I do. So what really happened, as many people do, as they kind of reach middle age, he had gained a kilo or two every year to the point where he was currently living with type 2 diabetes. And I think this was a real shock to him. And the kind of standard advice at the time was just, you know eat less move more continue eating your carby foods that we all do today but he was looking kind of for a different approach than this and he he spoke to a number of scientists who were doing this really cutting edge research at the time and what he eventually developed was the 5-2 diet and this was a diet in which many people will be familiar with now and you know multiple politicians and celebrities around the world started using this.

3:17And it was very simple. So five days a week, you eat normally and two days a week, you eat 800 calories a day. And it worked really well for him. He reversed his type 2 diabetes, he lost nine kilos. And with a little help from my mum, he was able to keep that off for the long term. But I've always really been fascinated by this area. And I did my own masters in research when I studied medicine. And that was with Roy Taylor, Professor Roy Taylor. He was a real hero of my dad too. So he was the first person really to show that type 2 diabetes was not this chronic irreversible condition that you could actually reverse it through a low calorie diet.

4:02And at the time, again, this was seen as unusual, It was seen as kind of crash dieting. But actually, what the studies show was that after a year, 46 % of people had reversed their type 2 diabetes compared to only 4 % in the control group. And that was being on the 5-2 specifically. So that was via a 800 calorie diet. But there has been a lot of research, again, to show that the 5-2 diet is a really effective way at losing weight. So it's about reducing calories effectively. That's what fasting is, right? And now I guess there are lots of other ways of fasting. people talk about I don't eat until 11 and then I shut my window of eating at 6 so they have a seven or eight hour window where they eat which has again proved to be quite popular and quite an effective way of losing weight.

4:48Is it just the same science that you're just reducing the calories in which is why it works or are you actually intrinsically changing your metabolism? So there is a combination of factors involved with fasting and there does seem to be some health benefits as well as the pure weight loss. When you really cut those calories down, you're kind of taking your foot off the accelerator and taking your car into the garage. Instead of putting your body in this kind of growth phase continuously, you are taking it into a slow down and repair mode. There was a recent study, actually, a 2025 study that looked at more than 20 different studies following the 5-2 diet and it found that people had lost significantly more weight, significantly more fat around their midriff, they lower their cholesterol and their blood pressure and that was compared to a kind of traditional diet.

5:41So it does appear to be really effective. So those two days, do they have to be consecutive? Is that important? They don't have to be consecutive. When you're doing that kind of continuous calorie restriction that can really wear you down over time. With the 5-2 diet you can select you know certain days of the week, where you think that would be a good day for you to do it. A lot of people do it, for instance, when they're on a work day. And I think the other thing it really highlights is what sort of foods are filling and what foods you're just going to burn off straight away. The 5-2 and other kinds of fasting were certainly, you know, as you say, big conversation, politicians, celebrities doing it.

6:18And then in the last few years, the noise and it is getting louder and louder is all about GLP ones. And we've discussed it already on the podcast, actually, the use of GLP-1s and where they can be very effective. You've become particularly interested in this because people are now coming off GLP-1s, aren't they, after a couple of years? And studies are starting to show that it's not necessarily been a long-term, effective long-term way of keeping weight off. What are the stats? When you look at the stats, it is quite remarkable. So these weight loss medications such as Zempik and Manjaro in the studies in 2021 there was a big study that showed with the medication is then people we go v that people were losing 15 of their body weight and that's compared to only two percent in the control group and then there's been more medications since such as manjaro where people are losing up to 20 of their body weight in the studies they are so effective at reducing your appetite and and silencing that food noise whilst you're taking these medications one of the problems with these medications is when you stop taking them, that food noise, it does come rushing back with a vengeance.

7:33And in the studies, after 20 months with this new generation of weight loss medications, then typically your average person has regained all of that weight. And that's between four and up to eight times faster than what you would typically regain with conventional dieting even. And all of those cardiometabolic markers will return back to baseline over a similar period of time. And is this something you touch on in your book, Food Noise? Yeah, I do discuss in the book. Some of these other downstream consequences of the weight loss medications are so you lose a significant amount of your body weight.

8:08We do also know that 25 to 40 % of that is lean body mass. A main component of that is muscle. So I do have concerns that people are losing you know significant muscle alongside these weight loss medications we kind of talked about the weight we gain well if people will be losing lots of fat but also muscle too when you put that weight back on it doesn't come back as muscle well muscle is more difficult to put back on it's much harder to keep muscle exactly so we we do reach peak muscle mass sadly at 30 so I'm already going downhill but but we know we talk a lot on the midpoint about the importance of weight training and keeping that muscle you know and how hard it is obviously as you get older to keep it but that's why it's more important to keep keep doing it so what you're saying is if you lose 15 of your body weight that is not just going to be fat there is going to be muscle in there and then when the weight comes back on unless you're doing it scientifically presumably and you're eating exactly the right amount of food and the right proportions of carbohydrate, protein and fibre and everything else that you need, and training to gain muscle specifically, you won't just gain muscle.

9:22It's not just going to come back on as muscle unless you're training it. Typically, whenever we lose weight, we do lose that lean body mass. This can really be offset by doing even basic strength training, even increasing your physical activity. and I think especially for people who have never done any form of strength training then they can see improvements so so quickly yeah it's very important to say it's never too late there's a really interesting study that showed it looked at two different groups of people it compared 85 plus year olds to practical youngsters 65 to 75 and what it found was in that younger group of 65 to 75 year olds um they increased their muscle mass by about 10 percent and their strength by 38 percent over that 12 week period and that was just by doing kind of weights but machine weights are quite straightforward no free weights or anything like that but the 85 plus year old actually increased their strength more they by 46 percent and their muscle mass by 11 percent because the baseline was already quite a bit lower so why yeah why is muscle important well it does have a lot of health benefits so it is strongly associated with longevity um it does reduce your risk of future frailty especially if it's functional muscle you're able to you know things that we take for granted now being able to get up off the off the sofa being able to mobilise but um keeping you more stable it's a great sink of blood sugar and it's um it also burns more calories actually so i know this is not your job to sort out that conundrum but if glp1s are so effective for people in losing weight um do they just have to stay on them then and can they stay on them if they're going to put weight back on afterwards or where's the educational piece in this for people do you know what i mean if they're taking these drugs it seems a travesty to then go and put all that weight back on.

11:21So what's the solution there, do you think? When you are on these weight loss medications to have the right nutritional and lifestyle strategy. Is that being given to people, do you think? Or are they seeking it out? And I think that is one of my concerns with these weight loss medications. So 95 % of people are getting them from online pharmacies because they're not widespread available on the NHS. So some are better than others, but not all are providing, in my opinion, and, you know, adequate support there. There's lots of different options. I think it is important to make sure you are very, you know, well-informed about these medications.

11:55I really am neither for or against these medications, but I do try and weigh it up in my book Food Noise. Another way would be a digital lifestyle programme like the Fast 800, which does provide 1 ,000 recipes and muscle and strength training. Programmes, yeah. So tell me about Fast 800. so so the fast 800 was a program that my dad was really passionate about and this was set up by my mom and dad so that was michael and claire mosley is they've been so passionate about this area and improving people's metabolic health it's like a kind of digital support program that provides health coaches and it provides these um a series of workouts and support and kind of behaviour change practices as well.

12:44And I think that does just take away some of the stress of deciding what to eat every evening. And I think it does provide a lot of flexibility for different, you know, different diets and different cuisines. So was it the rise of GLP-1s that made you want to sit down and write food noise then? Because the noise you talked about earlier, people who tell me they would really like to try these drugs because they just can't lose weight or they find themselves kind of fighting this voice almost, this noise inside them, which is telling them to eat when they're no longer hungry, basically. In fact, Oprah Winfrey actually articulated it quite well, didn't she, when she talked about the noise, that it's the first time she's ever experienced in her life when she took GLP-1s, the noise going off, basically.

13:30If we actually look at, you know, the rise of obesity over time. So back in the 1960s, it was between one and two percent in the UK. People living with obesity to over 30 percent today. So we haven't had this collective collapse of willpower. So there is clearly something in the environment. And I think part of that is the rise of these, you know, these processed junk foods that are designed to be overeaten with the perfect combination of salt, sugar, fats and refined carbs. So the environment, the change in environment, I think, is a big factor. and clearly there is a big genetic component as well and we have seen that with twin studies.

14:12Some people are much more likely to gain weight than others but also we talked about this food noise, some people suffer from it a lot more than others as well so it is really difficult for people to lose weight in the food environment we do live in. And what kind of studies have been done though to, as you said there, There hasn't been this huge kind of global collapse in willpower or at least national collapse in willpower that has given rise to the obesity epidemic. So what is, apart from, you know, processed food is more available. You don't have to eat it. Once you start eating it, I mean, we've had Chris Van Tuken on the podcast as well.

14:50So we've talked about a lot about processed food. once that becomes the main kind of a component of your diet are you changing your metabolism in such a way or are you changing the noise internally in such a way that you know the only way to turn it off is either you're going to kind of have to completely cut these foods out and go fast or do something else or you know is it possible just to wake up and and say I mean I know you can't say this because this has not been your experience but from what you've seen and who you've met I'm just intrigued to kind of know how how people are going to be able to turn it off without GLP ones yeah there are so many different factors involved in in losing weight so and diet is just one of of a number of factors and I think it is so important to address all of those things too when I first started working as a junior doctor I was you know I was very stressed I was trying to find my way in the hospital I was going on long commutes to work and I was you know eating eating sweets on the way to work on the long ward rounds I would be eating boxes of chocolates that were given by grateful patients and I would have a nice beige lunch because I was tired after work I'd probably just be putting on a ready meal or something option not the way you've grown up no no exactly so I have always been interested in you know health eating and I wasn't prioritizing my sleep.

16:16I wasn't, I kind of had stopped exercising too. I was probably drinking a little bit too much as you know, you're meeting new people. I'd moved to a new city. So, so I managed to pile on 15 kilos of fat over less than a year. And I think I'd got weaker in the gym. So I'd obviously lost a bit of muscle as well. So I, you know, as I kind of found my way in the hospital, I kind of started planning my meals a bit ahead of time as I got less stressed and started exercising again, prioritizing my sleep. I did just gradually lose that over time but I kind of I do understand how easy it is yeah yeah when you went home I guess presumably you're pretty much based did your family did your dad and your mom I think I mentioned something but I won't say what she said it wasn't that bad but it was very nicely nicely put that's that's good because I think my kids would say I'd be much more harsh if that happened yeah so so you realize yourself okay even though it's crept up on you over that time exactly why it happened you're eating rubbish basically you're putting nutritionally very um low quality food inside your body you're eating sweets not moving and drinking more alcohol so it's quite it's clear to see isn't it where that equation what it what it equals and it equals you becoming a bigger person and getting close to being an unhealthy person so you decided to make those changes and did you follow fasting did you do five two so i haven't i haven't uh personally followed the 5-2 diet myself.

17:43You just went on a better. Yeah, I think I just started kind of following a Mediterranean style diet. And it was just simple things like planning my meals a little bit ahead of time and even things like exercising. So I was less stressed. Eating a lot of these foods isn't classified as an addiction. There is no real food addiction as, you know, as a guideline suggest we do see these foods do stimulate your reward systems and they do seem to change your reward centers. And again, this is one of the ways the GLP-1 medications work. So yeah, just talking a little bit about the GLP-1s here, they slow down your digestive tract and keep you full for longer.

18:32They act kind of centrally on your brain in areas like the hypothalamus, which is like the thermometer, kind of one of these key centres in your brain. But they also do affect your reward centres. Right. So they slow down your appetite effectively. So you'll feel fuller for longer. If they're doing that, if they're quietening something in the brain, and if you as you say food addiction is is not often kind of classified so much as an addiction but a lot of people who would say that they feel they've had that why does it not work or can it work for other addictions drug addictions alcohol addictions there is some evidence now actually that that they may reduce your cravings for some of these other addictive substances so the best well studied of those is is alcohol so there was a recent study last year that where they looked at I believe it was around almost 50 participants.

19:28And they separated them into two groups with a placebo and then the GLP-1. And they found that in those living with obesity and an alcohol use disorder, then it halved the number of heavy drinking days, significantly reduced the amount of alcohol they were drinking and even reduced the amount they were smoking too. So that was a really interesting study. I think there's a lot more studies needed in that area of addiction. But I was going to say, you've already stated that people are putting weight back on when they come off them. So if they use a GLP-1 to try and help reduce alcohol, presumably once they come off them, they haven't sorted out the problem that led them to drink in the first place.

20:09And that's potentially still there, unless it's another part of the brain that's, you know, being activated. It's a lifestyle thing. And then they're not doing the things they did before. They're not going to the pub anymore or they're not buying the wine and, you know, like they were on a daily basis. So I guess you won't know until that study is done. but it would point, wouldn't it, to behavioural changes also needed? Without a doubt. So they have sometimes been described as a, you know, a sticking plaster. They are not necessarily solving those intrinsic issues. And I think it's also important to say even within alcohol, that was only within people who are living with obesity and an alcohol addiction.

20:49Right, not people who just... So people who are... In fact, they have actually looked at it in people who are of a healthy weight in and it doesn't appear to be anywhere near as effective. So there is something interesting there. And again, these weight loss medications, they really are only for someone who is living with obesity and obesity related diseases, really. For those people who have tried all these other dietary approaches. And I think we've touched upon a few a few here, really. and you know you are still finding it really difficult because of the food environment and because of that that really distracting food noise for some of these people the they the weight loss medications can help but they are not a quick fix you still need to you still need to put in the kind of hard work whilst you're on the weight loss medications and you need to make some of these behavioral changes and ingrain some of these uh habits in my head i've got this number of two years is what you're you know the maximum that people are supposed to be on is that actually written down somewhere in you know the the doctor's manual so is that just an arbitrary number i've come up with so there was an initial idea especially within the nhs that they would be prescribed for two years but there is a problem with that and that's part of these kind of studies we have talked about um where you do just regain that weight right most well most people will regain that weight.

22:13Now the NHS is at least they're talking about when people stop these weight loss medications that they have to provide support for patients for at least a year after after they stop and provide this extra kind of behavioural support and this wraparound support. So really I mean it's common sense if you're learning about nutrition doing exercise and all of those things that we should do to keep a healthy weight while you're on the GLP ones you're more likely afterwards to be healthy and to not put the weight back on. If you've done nothing proactively other than just jab yourself and it means you'd want to eat less, you're less likely, of course you are, to then keep the weight off because you haven't learnt anything about the way your body functions with food.

22:56So there needs to be an educational piece, clearly. And as you say, worryingly, 95 % of GLP-1s are kind of on the dark pharmacy market and they're not being prescribed by the NHS in this country? Yes, so 95 % are prescribed by pharmacies or online pharmacies, private. For them, there's no regulation when they prescribe the GLP-1s that they have to do anything else other than send the drugs out. I think there are definitely plenty of good online pharmacies out there and some do provide support and some do provide more than others. And at the end of the day, with some of the regulation, I think would be really important to bring in.

23:35I think at the bare minimum, there should be a video consultation. And again, that will help reduce people who don't need these medications from accessing them. So we've kind of mentioned a ZenPic that acts on this one receptor. Manjaro acts on two receptors, so it's more effective. Now, there's this medication coming out called retatutide, which has been described as a Godzilla of weight loss drugs. And this acts on three different receptors, and it's as effective as bariatric surgery. So that's when you perform major surgery and significantly reduce the size of your stomach. Now, this medication is coming out this year.

24:16Some people are already able to access knockoff versions of this, like I say, online, but these are completely unregulated versions. So stay away from those kinds of things, presumably. Exactly, yeah. I would 100 % let's stay away from them because there's no regulation really at all with them. Some of them contain the wrong ingredient. There have been stories of people who have taken triple, quadruple the dose of the medication. There's stories of people where it's insulin instead of GLP ones and others where there's significant bacteria in it. And this could lead to serious infections too. So that is a completely dark market of that.

25:00Can we talk about, I've heard people talking about microdosing GLP-1. So healthy people with, you know, very good body composition and weight because of the other benefits that are being muted to come from GLP-1s. So whether that's to do with brain health, heart health, various other benefits to our bodies and our brains. how do we work out what you know where the improvement is just because of weight gain and weight loss and where it can happen just because these drugs are improving or helping with heart health and various other things especially when you've just told me this is the heart thing i don't get heart's muscle right if you're losing weight how is that affecting the heart so we do know they can reduce inflammation and that's like a kind of slowly smoldering fire that can slowly damage your organs over time.

25:57But when you are living with obesity, you are definitely at high risk of having this inflammation, especially as some of that fat can overflow into your organs and especially this nasty visceral fat, which is metabolically active. So just looking at some of the studies you see with people living with obesity over a kind of five-year period that, yeah, a quarter of it reduces is a risk of heart disease by a quarter, chronic kidney disease. It does reduce the risk of type 2 diabetes. And there has been an association with a reduced risk of things like dementia. But even we do know a lot of, particularly Alzheimer's and vascular dementia, they are massively increased when you do have poor metabolic health.

26:45For instance, if you have type 2 diabetes, that doubles your risk of these conditions. so we still haven't really tied out whether there is this independent glp1 effect but i suppose the question is would i be better off just being healthy weight eating well exercising um will that be enough to to get the benefits to my heart and brain health or that same person with a little bit of you know microdosing does that everybody wants to be the extremely healthy version themselves don't they so i suppose until that question is answered and you say there haven't been studies to conclusively prove that yet yeah then we're not we're not into microdosing just yet we're not because these medications have been studied extensively in people who are you know overweight or living with obesity they haven't been firstly they haven't been studied of in people of a healthy bmi so i would be very wary and at that point that risk to reward ratio that you you know you always actually take with any medication or intervention.

27:50I suspect it will move more towards the risk end of things. But we still don't really know what the future will be with these weight loss medications. And as I mentioned, you know, with this weight regain, for some people, it may be that they are staying on these medications for the long term and at a bit of a lower dose. but for other people if they do you know ingrain those right nutritional lifestyle habits then I hope some people will be able to use these medications as a kind of way to yeah minimise that distracting food noise and improve their health. So your book Food Noise who is it aimed at?

28:34It's aimed at anyone who is interested in the GLP-1 weight loss medications or anyone interested in other kind of dietary approaches to weight loss and I go into a lot of that in this book and I think it's anyone who's even interested at all in the in the GLP-1s even from a kind of curiosity point of view because I think it is such a fascinating story of how they originated um and there's a lot of interesting and kind of some of these ethical issues really uh involved with the glp1 medication and i would also say these weight loss medications like i said they're not i'm neither kind of for or against them so i'm trying to give a really a balanced approach in this um and what is very clear though is these weight loss medications are they're not going any way anytime soon there's 200 in the pipeline so they're making a lot of people a lot of money aren't they there's an arms race between big food and big pharma i think the one plus side of that is you know as there is more competition they will become cheaper and maybe more available to people who could benefit from them but should we not be you know to bring chris van should we not be changing the way that we're presenting food to people in the first place when we understand so patently that processed food is not good for us and can lead to serious health consequences it just i don't know it just feels slightly mad that we're you know we're pushing both still we've kind of talked about i think there should be some regulation within the GLP-1s, but potentially there should also be more changes within the kind of food environment.

30:24The idea of taxing some of these really unhealthy junk foods and using that money to subsidise whole food. But I think, again, people like Chris are doing really incredible things in this space. Tell me, children, are they not allowed GLP-1s? Is there a legal age? so yes so children aren't allowed anyone under 18 but i i understand that i believe they are actually looking at you know using them in some people as um well as young as 12 going forwards at least they are they're researching this um and yeah and i i yeah i don't know exactly where things will go from there because if you do start using them at such a young age then there could be this thing that you might be on them for life so and what are the um well we haven't even had them for that long have we so the um what's emerging as the major complications or downsides from the drugs apart from the nausea that people report which i suppose is is just a kind of temporary thing while you're on it some of the immediate sort of side effects that are quite common they are they're linked to the way they do slow down your digestive tract and those are some of these common things like nausea, vomiting, diarrhea, constipation.

31:45Yeah, not fun side effects at all. And again, some of these side effects can be reduced by changing, making dietary changes, which I kind of talk about. Then there are some of these more serious side effects, which are fortunately still relatively rare, but they are something to consider, especially with things like Manjaro does seem to increase the risk of pancreatitis, and that's inflammation of your pancreas this is a potentially you know serious condition which causes severe abdominal pain gallstones anyone who does lose weight quite quickly is at risk of gallstones other things like which are less talked about things like bowel blockages so that's bowel obstruction which again that can be a really concerning condition and yeah I kind of touched upon things like some of these downstream effects, including that muscle loss.

32:39But another factor I would be concerned about is if people are just eating kind of the same potentially low quality diet that they were eating before and not making those dietary changes, then they are at increased risk of malnutrition and some of these micronutrient deficiencies. Robbie Williams was taking these weight loss medications um he he talked about developing scurvy which is a gosh condition of you know 16th to 17th century sailors and sailors exactly where you couldn't get any fresh food for months at a time yeah it's not a decision to be taken lightly and i think that's something i kind of do look into in in the book and um the other thing i do talk about is some of these um my I yeah, my mum who works in tandem with a nutritionist, she's written a lot of bestselling books when she was doing things with my dad.

33:37And they they pulled together these 50 nutritional recipes in the book so that you do you stay nourished. You support yourself. You support yourself. Yeah, that feels to me like it's kind of the the education piece is the thing that is letting a lot of people down, isn't it? when they come off these drugs. So they are miracle drugs for some people in many, many ways. But if we don't combine that with education and people changing their lifestyles, then it feels like they're just, you know, it's a two-year exercise and then it's gone, isn't it? So thank you so much, Jack, for coming in and telling us all about GLP-1s and your book Food Noise, which, as you say, has plans, recipes, and ways of keeping that weight off once you come off the GLP-1s.

34:21And as you say, if you're interested at all in the history of the drugs, then you go into that as well. So thank you. Thank you so much for having me, Gabby. I've had a great time. Thank you. Thank you.

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