ZOE Science & Nutrition - Most replayed moment: The hormone that controls your weight | Dr Andrew Jenkinson

Episode Date: September 8, 2026

Floating through all of our bodies is a complex network of hormones. You can think of it as an internal postal service, delivering vital messages and instructions to different organs and systems. But what happens if these messages get intercepted, mixed up, or worse, not delivered at all? In this episode, Dr Andrew Jenkinson tells us about a hormone that plays a crucial role in weight regulation and the undesirable consequences when it isn’t functioning properly. He also shares three simple tips you can do tomorrow to make sure your hormones support your health. 🌱 Try our science-backed and tasty wholefood supplement Daily30 🌿Let your gut microbes snack on the ZOE Gut Health Bar Get our brand-new app and Gut Health Test designed by world-leading gut health and nutrition scientists to build healthy eating habits 👉 Join ZOE Follow ZOE on Instagram. 📚Books by our ZOE Scientists The Food For Life Cookbook Every Body Should Know This by Dr Federica Amati The Appetite Reset by Dr Federica Amati Food For Life by Prof. Tim Spector Ferment by Prof. Tim Spector Good Mood Food (preorder) by Prof. Tim Spector Free resources from ZOE The Smart Snacking Guide: How to feed your gut, fuel your day, and snack without guilt The Hormone Harmony Guide: Tuning Your Body’s Internal Orchestra   Eating for Better Brain Health: Your brain-gut blueprint How to eat in 2026 - Discover ZOE’s 8 nutrition principles for long-term health Live Healthier: Top 10 Tips From ZOE Science & Nutrition Gut Guide - For a Healthier Microbiome in Weeks  Better Breakfast Guide Have feedback or a topic you'd like us to cover? Let us know here Listen to the full episode here

Hello and welcome to Zoe Recap, where each week we find the best bits from one of our podcast episodes to help you improve your health. Floating through all of our bodies is a complex network of hormones. You can think of it as an internal postal service, delivering vital messages and instructions to different organs and systems. But what happens if these messages get intercepted, mixed up, or worse, not delivered at all? In this episode, Andrew Jenkinson tells us about a hormone that, that plays a crucial role in weight regulation and the undesirable consequences when it isn't functioning properly. He also shares three simple tips you can do tomorrow

to make sure your hormone support your health. So there's one hormone, the master controller, leptin. Skimmed over in medical school, not too many doctors really understand it too much, but it's like absolutely crucial in human weight regulation. And mammalian weight regulation. If we're in an environment where there's no food, we're sort of okay for 60 days,

That's a long time to try and find some food. And then we start eating into our muscle and whatever and stuff to become very, very sick. So 60 days is, you know, a human is hardwired to carry. We're not hardwired to carry 120 days. We don't need it. It's going to drag you down. You're not going to be as fast. You're going to be from a, you know, evolutionary point of view, at risk of predation.

You know, so those people who were big, they didn't pass their genes on. So how is that regulated? Because it is. Because it's really, really important from a suffice. or perspective, this homeostasis, this regulation of that 60 days. Basically, it all evolves around leptin. And leptin is a hormone that is produced by our fat cells. And the more fat cells that we have, the higher the leptin level. So leptin comes from the fat, goes into the blood. And that really important area of our brain, hypothalamus, which is the master controller of our weight, will sense the level

of leptin in our blood. And it will think, okay, we're, um, the level of leptus. The level of, um, the Epitin level is quite high. I think we've got maybe 70 days or 80 days storage. The tank is really, really full. We can ratchet down the appetite. We can be not that interested in food. We can increase the metabolism, that dimmer switch. Seamlessly, without any, you know, any thoughts, your weight will go back down towards, you know, the weight set point, basically. And the same thing happens the other way. If we lose weight, if we go on a calorie restriction diet, or if we get sick and we don't eat much and we lose weight or if we're in a famine environment, that level of leptin will decrease because our fat has decreased and there'll suddenly be an alarm. So the hypothalam will dip into the blood, it will see the leptin level has gone down.

Think, oh God, okay, we're in a famine situation. Brach it down the metabolism so we don't burn off too much, go into battery saving mode, but actually be looking for food. And this, you know, from an evolutionary perspective, is the thing that kept us within that target range of around about 60 days of energy storage. Now, if that's working, why does anyone become fat or store far too much energy? Sometimes a year's worth of energy. What is the point of that? That is a disease. Something's gone wrong.

Okay, so something's gone wrong with leptin. It's called leptin resistance. So if you measure someone who's really suffering with obesity, you measure their leptin level, it is sky high. It's like triple what ours would be. So why is that not working? Why is the hypothalamus not able to see it? And it's because it's being blocked by this other hormone that we all know, insulin. Insulin and leptin share a receptor pathway in the hypothalamus.

So the more insulin we have, the more dilute the leptin signal. So you can be walking around with very, very high leptin levels, but actually because your Western diet has foods that stimulate high insulin, so sugar, highly refined carbohydrates, and a snacking culture, which we have. Your insulin levels are, on average, raised. That dilutes the leptin signal, and the brain can't see the leptin anymore. Despite you carrying far too much weight, it can't see it. You know, it's blocked.

It's leptin resistant. And then you get the opposite signals or responses from the hypothalamus that you should get. Because it can't see leptin. It thinks that you're fading away rather than you're carrying far too much. much weight. So you will get totally inappropriate signals of hunger and low metabolism. And this is the crucial thing, Jonathan. So, you know, when you understand leptin resistance, these factors that society and doctors blame on obesity as poor character traits. So being a little bit too hungry, a little bit too greedy and a little bit too lazy, that is not the cause of the

condition, that is the symptom of the condition. So when you've got leptin resistance, you become hungry and you become quite tired because your metabolic raise has been turned down. It totally flips the whole concept on its head, you know. Actually, this is a symptom. This is not the cause. And that symptom then drives up the, you know, the weight set point. And this is the reason that people's weight set point will go from normal up, up, up, up, up, because leptin has been diluted by the insulin signal. It's also diluted by inflammation, but that's a separate thing. If you understand the insulin blocking leptin side of things, you're going to start to empower yourself to be able to change your weight set point. And so I think you're saying that the food that we're eating has a

really important impact, not thinking of it now in terms of calories, but actually the sort of food we're eating is leading to much more of this insulin in our blood, and therefore our brain is sort of not sensing anymore. Hey, you're carrying around enough fat and you've got the 60 days you're talking about, I don't need anymore. It's like not able to see this anymore. And they say, oh, like need to eat more food because clearly we haven't got enough storage to be safe for the next famine. So this is really explained, I think, in a lovely analogy called the empty gas tank. So imagine you're driving along the highway and suddenly your gas tank meter is flashing red. And it's like, oh, God, you're going to run out of gas or pet,

And you start panicking a little bit and thinking, God, they've got to fill up in the same way as if your hypothalamus wasn't seeing leptinot think I'm starving. You get to the gas tank, you start filling up and you realize, well, hang on, the gas tank is already full. Now, the problem is, the gas tank meter is broken. And this is what leptin resistance is. So you've got these people with full gas tanks, but the gas tank meter is broken. They feel like they need to fill up. That warning light is flashing all the time. But unlike a car where you can't fill up more than full, you can in a human.

I would love now to talk to like what could listeners do to actually either achieve sort of sustainable long-term weight loss or ensure that like their set point remains stationary. So could we maybe start with what people are eating? How does the food that we're eating affect this? story. The first thing that we've nailed is it's not about the calories. You need to understand that it's all about your set points. So you can try and calorie count. You can try and go to the gym. You can lose weight for a month or two months or you can lose weight for six months, but you're going to feel terrible and it's all going to come back on eventually unless you understand why your set point is set so high. And you've really got to address the amount of insulin that you're taking in. So

If you can decrease the amount of insulin you're taking in, you will release that leptin signal. So if it's working, you will get back towards a normal weight. We've got to go on a sort of that type of lowish carbohydrate diet that is doable that we can live with. My book goes through various different phases of that diet. And the first thing would be, you know, the real enemy is sugar. That's the first enemy anyway. So if you can maybe do a 30-day giving up, sugar and sugary food challenge. That would be the first thing. It's going to take a little bit

of willpower because we haven't even gone towards, you know, the dopamine reward pathways and what sugar does to us and how it is basically a legal drug that we're all addicted to and, you know, habitually take. But, you know, if you can get a head around all those things and actually give up sugar for a month, that's the first thing. You will lose some weight. Your insulin levels will increase slightly and you will release that leptin signal a little bit more. and naturally your weight will come off. Okay, so first thing, give up sugar. Second thing, second month maybe, don't snack between meals.

Just have three square meals a day. Try and embrace hunger. You know, do what the French do. Don't snack between meals, but eat really well and enjoy food when you're having the meal. Constantly snacking is something that, you know, is new, something that only in the last sort of 30 years or so has just become a norm sort of eating

confectionery or crisps or whatever on the tube or whatever in the street because you're starving the reason you're starving is because your glucose levels are going up and down because we're on a very high high carbohydrate diet so we're off the sugar we're off the snacking third thing processed foods if you can then give up the processed foods

and you know really embrace healthy, old-fashioned food, you know, the food that your grandmother would have cooked, fish, meat, any type of vegetable and dairy products. Is there anything else that's important that could really support this sort of long-term reduction of your set point and reduction of your weight? Good question, Jonathan. And there is, because cortisol is very, very important. Cortisol is the stress hormone.

If we have too many stresses at work or at home, that's going to have. increase our insulin. You can do everything, but if you're one of these very, very stressed people, it's almost like you're a scared animal, your body doesn't want to lose weight. So de-stressing, either by unpecking work or family issues or being able to have relaxation techniques, is really important for weight loss. So you'll decrease your cortisol level, you know, your insulin level will normalize. Leptin signal will be released. Exercise has a similar thing. You don't lose weight by exercise by burning off the calories. You lose weight by making insulin more efficient and decreasing cortisol.

That's why gyms are popular. It's not to do with burning off calories. And the third thing is sleeping really, really well. So sleeping again is really important for our relaxation, our cortisol, etc., etc. So these things de-stress, a little bit of exercise that you enjoy and sleeping well. Finally, if you could give one piece of advice to anyone who's listening to this, who's trying to lose a significant amount of weight, what would it be? I think it's really to understand that it's not the calories in the food,

it's what the food does to you metabolically. So avoid sugar, avoid refined carbohydrates, avoid processed food, don't snack all the time. You will lose a lot of weight just by doing that.