Is Your Body Working Against You?
You know the feeling: you start eating right, working out, you’re seeing some progress and then… your body just stops responding. Over 80% of diets fail, but WHY? Juna and Eddie talk to Dr. Paul MacLean, Professor of Medicine and Pathology at University of Colorado School of Medicine, about what happens at the end of a diet and the biological drive to regain weight. Tune in to find out what happens to appetite, movement, fat storage and more AFTER the diet.
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Guests
Dr. Paul MacLean is a Professor of Medicine and Pathology at University of Colorado Anschutz Medical Campus. He specializes in obesity research, the metabolic consequences of obesity, and strategies for long term weight reduction.
Academic Profile | Publications
Studies
The Role for Adipose Tissue in Weight Regain After Weight Loss
Biology's Response to Dieting: the Impetus for Weight Regain
Terms
Energy Gap - The difference in the calories you want to eat and the calories you expend resulting from the increased appetite and lowered movement experienced at the end of a diet.
Obesogenic environment - anything that promotes obesity (Ex. sedentary lifestyle and easy accessibility to refined sugars and highly processed foods)
Homeostasis - The tendency for your body to maintain equilibrium in any given physiological process. The body’s internal thermostat.
Leptin - a hormone produced by fat cells, which is a sign of adipocytes a.k.a fatness. When you lose weight, fat cells are shrinking and producing less leptin.
Hypertrophy - the enlargement of an organ or tissue from the increase in size of its cells.
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Juna: Food We Need to Talk is funded by the Ardmore Institute of Health, the home of Full Plate Living. OK, Eddie, when we talk about weight loss, how often do you think people try diets?
Eddie: A lot.
Juna: And how often do they succeed?
Eddie: A lot.
Juna: But how often do they regain the weight?
Eddie: I'm going to say a lot -- about 80 percent of the time, to be precise.
Juna: If you've ever gone on a diet, lost weight or started a new exercise program, you probably know the feeling well. You're working really hard and things are going well. You hit a new low weigh in. Fast forward a few months and the weight is back.
Eddie: I see this in my patients, Juna, and it could be so frustrating to have worked so hard for something only to have your body almost ricochet back. A lot of these changes are hard to make, and if they're not working, it can be demoralizing. It's almost as if your body wants you to be heavier.
Juna: That is what we're investigating today. What happens when we diet that makes us so likely to regain the weight? Is there a certain weight that your body just wants to settle at and can we change it? I'm Juna Gjata,
Eddie: and I'm Dr. Eddie Phillips,
Juna: and this is Food, We Need to Talk the only podcast that has been scientifically proven to shrink your fat cells just by listening. Our guest for today's episode is Dr. Paul McLean, professor of medicine and pathology at the University of Colorado and Shoot School of Medicine. Out of all of the research I've seen working on this show, Eddie, I have to say Dr. MacClean's research, it's a big. Tough a bummer, and I'm not alone, apparently.
Paul MacLean: I have to tell you, my wife hates the research I do because other than the exercise component, she just gets really depressed with what I have to say.
Eddie: So wait, what does Dr. MacLean actually study?
Juna: Well, it's the thing that we've all experienced firsthand that seemingly inevitable propensity for your body to regain weight. So the first thing I wanted to ask Dr. McLean is whether set point is a real thing. Is there a particular weight that your body just wants to stay at? But it turns out it's not that simple.
Paul MacLean: I don't think of the set point is really set or a particular point because it can be influenced greatly by things like how much we exercise or the types and amounts of food that we eat and the environment around us, the choices that we make. But for all of us, we're subject to our underlying genetics. Some of us have genetics that are susceptible to weight gain, and in this particular environment we're living in and others are less susceptible.
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Eddie:The environment we live in today is very different than the environment that we lived in even 50 years ago. First of all, we have a radically different food supply.
Paul MacLean: Over the last 50 to 60 years, the availability of energy dense foods, processed foods, highly refined sugars, all of that has become very readily available to us.
Eddie: This is something that we talk about all the time on the show, and on top of that, the way we live has also really changed.
Paul MacLean: At the same time, the lifestyles that we've had to leave to earn a living has become one that's more susceptible to less physical activity.
Juna: This is what researchers call an obesogenic environment
Eddie: Which by definition is anything that promotes obesity that is the genesis of obesity.
Juna: See what you did there,
Eddie:Too many easily available calories, sedentary behavior, insufficient sleep and certain medications.
Juna: And I know what you're thinking, guys, blah blah blah old news. Food supply is unhealthy. We don't move enough really, really groundbreaking stuff here. But hold your horses because we're about to talk about some rats in the lab.
Eddie: Is it just me or do we talk about rats more than your average health podcast?
Juna: Shh Eddie, don't tell them you'll expose us. So in Dr. McClean's lab, they subject rats to a similar obesogenic environment. Lots of access to high fat, high sugar foods.
Eddie: So it's like a rats version of cookies and chips.
Juna: Basically, yes. And they even have rat treadmills if they can convince the rats
Eddie: how cute
Juna: if the rats even actually can be convinced to go on them.
Eddie: So pretty much like the world we live in today?
Juna: Exactly. And what they found was there was two types of rats: obesity prone and obesity resistant.
Eddie: And I'm guessing from the name obesity prone rats gained a lot of extra weight, and the obesity resistant rats didn't.
Juna: Eddie, this is why you're the doctor in the room. You're always coming back with the hard answers. So if all these rats are in the same environment and all over eating the same amount, why are some rats gaining a bunch of excess weight and others aren't?
Paul MacLean: So what happens with the obesity resistant rats where they were able to sense that higher level of fat that they were eating. And so what they did and what we saw in these rats is that they increased their energy expenditure and they were able to dissipate or expend those excess calories away. And they adjusted.
Eddie: So this goes back to that first law of thermodynamics that we've talked about for the last two episodes. Juna, all the energy that we eat has to go somewhere. So even for the rats that don't gain weight, it's not something magical going on. They're somehow increasing their energy expenditure.
Juna: Meanwhile, our friends, the obesity prone rats,
Paul MacLean: they brought in more calories, but their bodies just did not sense that they had an excess number of calories coming in and they just kept eating until they gained weight. And that mass that they gained matched that level of over feeding.
Eddie: As we talked about in our last episode, the biggest portion of your metabolism is your basal metabolic rate, and most of your BMR is controlled by your size. Larger people burn more calories than smaller people. As you gain weight, your metabolism goes up as well because, well, now you're a bigger person, you have more cells, more tissues and more stuff that needs energy. So these rats basically keep eating until their size has raised their metabolism enough to balance their excess food.
Juna: Now, the reason for studying these rats is we think that something similar may be going on in humans. We're all exposed to the same obesogenic environment, but clearly there's a huge variation in how we respond to it. And the thing is, the way we respond is mostly subconscious.
Paul MacLean: It's a very complicated process. Homeostasis involves a complex set of nodes of regulation that span from the brain out into key metabolic tissues of the body, including skeletal muscle, adipose tissue and the liver. We don't know how all of these integrate to create a position of where your body wants to be at.
Juna: Just a quick note here, guys. Homeostasis is the tendency for your body to maintain equilibrium in any given physiological process. So think of it as kind of your body's internal thermostat
Eddie: and the exact details of how your body is maintaining its weight. Its homeostasis are really perfectly understood, but we do know that the process starts in the brain, specifically the hind brain and hypothalamus. You majored in cognitive neuroscience. Please explain.
Juna: OK, I'm so excited that my major's actually going to come in use for once in my life. So the hind brain is actually one of the most primitive parts of the brain, and it regulates things like your breathing, your blood pressure and other things we're not really conscious of.
Eddie: And your brain is constantly getting information from different parts of your body, but it's also sending out information.
Paul MacLean: Those areas of the brain in a very complex process send signals out to these key metabolic tissues to tell them how to use fuel. How to store excess nutrients. And how to adjust their efficiency.
Juna: Now, I know some people may be listening to this and thinking darn homeostasis. Why would it just let me do my thing and get ready for the beach? See my abs? But guys, it's the exact same homeostatic mechanisms that stop you from losing tons of weight, which also stop you from gaining tons of weight.
Paul MacLean: The homeostatic system has two objectives in situations where there's an energy deficit. It helps save us and become more conservative and seek out food under those circumstances so that we don't waste away to nothing. And then in the other direction, when food is plentiful, there are mechanisms that help us reach a plateau or a maximum to prevent us from gaining weight infinitely.
Juna: I don't know, man. It sure seems like the biological systems to stop me from losing weight are a whole lot stronger than the ones that stop me from gaining weight, if you know what I'm saying.
Eddie: Well, that's not a coincidence. Our bodies have evolved to deal with food scarcity for thousands of years. Food overload, that's pretty new. So the mechanisms that protect against weight loss are definitely much more powerful.
Juna: But I'm still stuck on these rats at the all you can eat buffet, Eddie, because there's actually a reason why we study these mechanisms in rats as opposed to humans.
Paul MacLean: So in animals, we actually have control over a lot of things that we don't have when we do a clinical study. And so we can control the animal's environment and animals are not subjected to some of the psychological pressures of, well, they want to look good in a bikini this summer. Their body weight is mostly dictated by their biology and the environmental pressures that we impose upon them. Humans have so many other things that can go in and affect the choices that they make. And so that's why it's a lot easier to focus in on the biology in animal studies.
Eddie: OK, Juna I know we're supposed to be talking hardcore science here, but I'm just sort of focused on this picture of the rats lining up at the all you can eat buffet and now they're getting ready for the rat fashion magazine.
Juna: So let's start talking about some of these mechanisms because honestly, once you start hearing the details, it gets real crazy, real fast. The first thing we're going to talk about is leptin. Eddie, can you give us a primer on leptin?
Eddie: Leptin is a hormone that's produced by your fat cells. It's basically a signal of adiposity. In other words, fatness. Oh, OK. When you lose weight, it's not because we get rid of fat cells. It's actually because the fat cells are shrinking and smaller fat cells produce less leptin.
Juna: So you're seeing your fat cells, a.k.a. adipocytes, if you want to be fancy are like little balloons. When you lose weight, they release lipids and they shrink down and when you gain weight, they suck up lipids and they balloon up.
Eddie: Mm hmm. Exactly. Leptin is your messenger of adiposity or your energy reserves. More colloquially, it's a messenger to your brain of how much fat tissue we have.
Juna: OK. And here's how your brain responds to these signals,
Paul MacLean: that signal of left in going to the brain, then is conveying a message that we are below the level of what our body norm is. And so that then tells the brain that we need to eat more and expend less so that we can replete those stores.
Eddie: Again, this makes a lot of sense. Your body needs a way to sense long term food availability, and fat stores are a great indicator because if there isn't enough food, your fat stores would be low.
Juna: Next, we're talking about a different hormone, probably one you've heard a lot about, and that's insulin. It turns out that losing weight can actually improve your insulin sensitivity.
Eddie: Wait, wait unit. That's a good thing. We want to have good insulin sensitivity. In fact, type two diabetes is characterized by impaired insulin sensitivity. So shouldn't we be happy about this?
Juna: Well, yes. But also it may make it easier for you to regain weight. We'll find out exactly how right after this break.
Eddie: Food We Need To Talk is funded by a grant from the Ardmore Institute of Health, the home of Full Plate Living. Full Plate Living, helps you add more whole plant-based foods to meals you're already eating. These are foods are already familiar with apples, beans, strawberries and avocados. It's a small step approach that can lead to big health outcomes. Full Plate Living includes weekly recipes and programs for weight loss, meal makeovers and better blood sugar management. Best of all. Full Plate Living is a free service of the Ardmore Institute of Health. Sign up for free at fullplateliving.org.
Eddie: And we're back! Juna, when we left off, we were talking about how when you lose weight, you improve your insulin sensitivity, and normally we think of that as a really good thing. But it may also make it easier for you to regain weight,
Paul MacLean: and improvement in insulin sensitivity is obviously a good thing. But what it also does, particularly with adipose tissue, muscle and liver, is it makes those tissues much more capable of taking up nutrients, storing them very efficiently and gaining weight back under conditions of over feeding. So good for metabolic health, but it really primes the system to gain weight back when overfeeding occurs.
Juna: A key point there is the overfeeding. Improved insulin sensitivity with no overfeeding is a good thing. But how many times have you gotten to the end of the diet and gone out with your friends to celebrate are gone and had a big cheat meal? And now that you have this huge amount of excess calories and very insulin sensitive shrunken fat cells,
Paul MacLean: those fat cells are now primed. When they see those nutrients, they're ready to suck them up, store them as fat in a very efficient way.
Eddie: Hold on here. Juna, what about the individuals who don't have excess weight and have always been insulin sensitive? Does that mean that their fat cells are also better at storing fat? Because if so, why would they still be lean?
Juna: Eddie, you read my mind. That's exactly what I asked Dr. McLean.
Paul MacLean: The insulin sensitivity looks very similar in a lean animal, as it does in a weight reduced animal. But the weight reduced animal has the added pressure of the brain, saying, I have got to eat a ton of calories.
Eddie: Oh, OK. So if you've been dieting, you are much more likely to overeat.
Juna: Yes. And when you overeat because you're hungry and tired at the end of your diet, your body is super quick in storing that energy. So it burns up all the carbs for energy, and it preferentially shuttles all the fat into your fat cells.
Eddie: So this is a really elegant, although perhaps infuriating,
Juna: elegant would not be the word.
Eddie: Are you all right? It's an infuriating function of our physiology. You've got the lower the leptin that makes you hungrier. Yes, possibly less physically active. While this improved insulin sensitivity makes your tissues better at storing fat if you do overeat. Your body is doubly ensuring that you don't starve and that you gain that weight back.
Juna: And we haven't even talked about the gut.
Paul MacLean: There's more when you eat your gut senses, food coming in and those systems become adjusted to favor what's called the hunger signals and to disfavor satiety signals. So it's it's like your gut becomes tweaked to become less sensitive to the nutrients coming in.
Juna: So the third layer to all of this is the mechanisms in your gut that usually tell your brain, OK, we've eaten enough. We have enough nutrients. They're are just much less sensitive at the end of a diet. So you don't get that signal to stop eating and all these mechanisms of things that are promoting hunger and making you feel less satiated and also making you move less. It's something that researchers call the energy gap.
Paul MacLean: The way that we have defined the energy gap is the difference between what the body wants to eat and what the body is expending. As we go through our normal day and we're not on a diet. What our bodies want to eat generally matches what it's expending right, and that keeps our body generally weight stable. So we're not gaining 20 pounds and losing 20 pounds on a day to day basis.
Eddie: I'm going to stick with elegant physiology because if you think about it, we're worried about gaining weight all the time. Yeah, but the average American is gaining maybe a pound a year. In the long run, it adds up, but on a day to day basis, that means that your body is really off by only a few calories a day. But when we go on a diet, all those signals shift.
Paul MacLean: And so what the body wants to eat is very high. And what our body is expending is very low. And that difference between that drive to eat, which I'm sure many people who have gone on a diet who get hungry, they experience this. That drive to eat grossly outweighs what our body is expending. And we believe that that is what represents the biological drive to regained weight.
Juna:This comes back to that idea of diet not being a transient state. Once you have lost a substantial amount of weight, there are actually biological consequences that you have to live with for as long as you want to maintain that lower weight.
Eddie: OK, so let's recap here we have hormonal changes and now the gut signals that make you much more likely to overeat and less likely to move.
Juna: Yes.
Eddie: We also have changes in tissues like adipocytes, so our fat cells plus muscle and liver, which make you much more efficient at storing the excess calories,.
Juna: Right.
Eddie: But then there's one more layer to it, which is we may have an actual expanding capacity for weight gain.
Juna: What?
Eddie: So remember how we talked about how the fat cells change when you gain or lose weight?
Juna: Yeah, they like blow up like balloons or they shrink down.
Eddie: Well, that's how things are supposed to work. As an adult, you pretty much have the same number of fat cells for your entire life. And when you lose weight, they're shrinking and when you regain the weight well they're expanding, that's called hypertrophy. OK, but the number is staying constant. It's always the same. However, something may actually be happening to the number of fat cells during large amounts of overeating post weight loss. Dr. McLean explains what he saw in his rats.
Paul MacLean: When we overfeed in our animal models, what we see is that there are certain signals that increase the number of fat cells during gross large levels of overfeeding. And now you have had not only your original smaller fat cells, but these rats now have a increased number of newly formed adipocytes so that when they gain all the weight back now, they have more fat cells than they had before. Now, this happens in our obesity prone rats. It doesn't happen in our obesity resistant rats. And so we think it might be happening in some humans, but not all humans.
Juna: Yikes. This is not what you want to hear if you've ever gone on a diet hearing. Gross levels of overfeeding is just giving me some strong post diet binge vibes. And here are the implications of this. When we study weight loss in animals, we basically put them on a diet and they lose some weight, and then we let them eat as much as they want and they regain the weight and they regain the weight until their fat cells are exactly the same size as they were pre weight loss to the micron. OK,.
Eddie: Well, that makes sense. That's the tightly regulated homeostatic mechanism we've been talking about.
Juna: Yes, but Eddie, if you have more fat cells and you're refeeding until they're the same size, that means you're regaining more weight than you started with.
Eddie: So what you're saying is the total amount of adipose tissue or fat is not what's regulating overfeeding. It's actually the fat cell size.
Juna:Yes.
Eddie: And if you're adding more fat cells, you're basically expanding the capacity of your body for excess weight.
Juna: Yes.
Eddie: I this topic is getting heavier and heavier.
Juna: Aha. OK, guys. He's too funny guys. So we should say these studies were only in rats. They haven't been completely verified in humans yet. So we have seen cases where humans have increased their fat cells, but we're not exactly sure. Is it because they're overeating post diet or is it just something that happens when we age? Eh, we don't really know. But it's definitely not something that happens to everyone. But it may explain the phenomenon that we often talk about on the show, Eddie of people gaining back more weight than they lost, especially when they yo yo diet high.
Eddie: When I talk to my patients, I always try to emphasize the positive, but I'm going to need a little assist to find the silver lining here.
Juna : OK? Dr. MacLean wants to make it very clear we are not our biology, or at least not just our biology.
Paul MacLean: Our biology is a really important pressure here. But there are other things that we, as humans do to counter our biology or to adjust the system and put pressure on energy homeostasis. And so we can make conscious choices.
Juna: Remember those reasons that we talked about how humans are so much harder to study than rats? Hmm. It's those exact reasons that give us autonomy over the response to our body.
Paul MacLean: Biology is not the end all, be all in the human condition. It's pretty much the end, all in our rats. But it is not the end all, be all in in humans. We can make conscious choices to eat better. We can make conscious choices on how much food we eat, when we eat, adjust our physical Activity levels and all of those environmental inputs and the choices that we make impinge upon that biological homeostatic system.
Eddie: I love that. That's pretty much the point of this entire podcast. Yes, we could sit here and dwell on the things that we can't control. But what's the point of that? At the end of the day, there are still so many things that we can control.
Juna: While you're about to be even happier because the one thing that Dr. MacLean says can be a real game changer in maintaining lost weight is exercise.
Eddie: Yeah!
Juna: Yeah, 80 to 90 percent of people who have maintained a significant weight loss -- So that's over 10 percent of their weight for over a year -- Report regularly exercising.
Paul MacLean: We believe that exercise counters a lot of those biological adaptations in the body to reduce the appetite and to increase energy expenditure. We don't think that you're just adding calories by exercising. We think that exercise increases energy expenditure even above and beyond the cost of the exercise bout. So that it makes weight regain more energetically expensive.
Eddie: Juna, this ties in perfectly with what we talked about at the last episode. Exercise is not the best tool for losing weight. It's not a huge calorie burner, but it seems to have biological effects beyond calories that make it crucial for maintaining lost weight.
Juna: And again, resistance training in particular. So something like lifting weights, getting stronger, increasing your muscle mass may be extra beneficial.
Paul MacLean: There's more and more data to suggest that resistant exercise has a very key contribution to a weight loss maintenance success. And that is because it can help sustain lean body mass, and it can help increase the metabolic requirements of your body, so it has the potential for reducing that energy gap between appetite and the metabolic requirements.
Eddie: See, I knew there had to be a silver lining.
Juna: Always the optimist you are.
Eddie: But what about the food? Is there anything we can do in terms of what we're eating to maybe hack the biologic system?
Paul MacLean: I think it's very clear from our animal studies and data and in clinical studies supports it: High fatty foods, processed foods, sugar, all of those things make it really difficult to be successful. So eating a healthy diet high in the good types of fats, the complex carbohydrates and the fibers, those types of things can have profound effects on that homeostatic system, not only with your appetite, but also in how the peripheral tissues metabolize and store the excess energy
Eddie: At the end of the day, these biological mechanisms shouldn't be depressing. The knowledge gives us the opportunity to be more conscious about our choices.
Paul MacLean: We can choose what to put in our pantries that could either help us or hinder our efforts for successful weight loss maintenance. We can choose to take the stairs rather than an elevator. We can choose to have a smaller portion size of that dessert rather than rewarding ourselves because we were physically active that day. That knowledge gives us a lot of power if we recognize what our biology is going to do. We can use strategies to counter that biological drive and give us a better chance to keep weight off in the long run.
Juna: And again, the most important thing is to never make a change that you don't think you can sustain forever.
Paul MacLean: We need to stop looking at diets as transient endeavors that will be started and stopped and then you go on with life. The strategies that you have used to lose the weight have to be maintained and sustained if you want to maintain that lower weight.
Eddie: And I think that's a great note to end on.
Juna: While we've cried, we've laughed. Now it's time to say goodbye, guys. You can find all our show notes, including links to Dr. MacLean's research at foodweneedtotalk.com. You can find the podcast @foodweneedtotalk on Instagram. You can find me at @theofficialjuna on Instagram and @JunaGjata on TikTok and YouTube. Let's be friends, and you can find Eddie preparing for his next Lifestyle Medicine Conference, which is going to be in June at Harvard. I have gone. It's such a good time. Food we need to talk is a production of PRX.
Eddie: Our producer is Morgan Flannery.
Juna: Claire Carlander is our associate producer, and Tommy Bazarian is our mix engineer.
Eddie: Jocelyn Gonzales is executive producer for Pyrex Productions Food.
Juna: We Need to Talk was co-created by Carrie Goldberg, George Hicks, Edie Phillips and me.
Eddie: Always remember, consult with your personal health professional for your health questions,
Juna: and to find out more, you can go to our website, foodweneedtotalk.com. Thanks for listening.
