MR. KOJO NNAMDIMost of us understand weight gain as a matter of basic math. We take in calories when we eat. We burn the calories we use for energy. And the leftovers are deposited as fat. But new research suggests that we may have it backwards when it comes to the cause and effect of weight gain. That it may be the process of gaining weight that's causing us to overeat, not the other way around.

MR. KOJO NNAMDIThis may explain why it's so hard to lose weight simply by promising ourselves that we're going to eat less. And why we may not have the kind of conscious control over our body sizes that we've been led to believe. Joining us to explore the science of hunger and its relationship to the modern food industry is James Hamblin. He is a senior editor at the Atlantic. He's a doctor who writes about behavioral health, nutrition, culture and preventive medicine. James Hamblin, good to see you again.

DR. JAMES HAMBLINThank you for having me, Kojo.

NNAMDIJoining us by phone is David Ludwig. He is the director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital and is a professor of pediatrics at Harvard Medical School. David Ludwig, thank you for joining us.

DR. DAVID LUDWIGMy pleasure.

NNAMDII'll start with you, David. So many of us have been led to understand that weight gain or loss is simply a matter of willpower, our ability to restore balance to that equation of the calories that go in our bodies and the calories that we use and go out. You've done a lot of research that suggests our basic understanding of that equation is off kilter. How so?

LUDWIGRight. Well, of course, losing weight is supposed to be simple, as you have indicated. Just eat less and move more. If it were so simple I'd be out of a job, quite frankly. The problem is, very few people can lose weight over the long term with low-calorie diets. And those who can't are blamed for lack of discipline and willpower. So according to an alternative view, weight is controlled like body temperature and a range of other biological functions.

LUDWIGEating too much refined carbohydrate is, by this theory, raised insulin levels and programmed our fat cells to suck in and store too many calories. When this happens, there are too few calories for the rest of the body. So the brain recognizes this and triggers the starvation response. We experience that as becoming excessively hungry and our metabolism slows down. A low-calorie diet doesn't solve the problem and actually makes things worse.

LUDWIGEventually we succumb to hunger and overeat. So a better approach, if this theory is correct, is to address the problem at its source by cutting back on the foods that are over-stimulating our fat cells, the refined carbohydrates like grains, potato products, concentrated sugars, especially the refined grains. And by eating this way, we can basically ignore calories and let our body weight control systems do the work.

NNAMDIIs it over-simplification to say that your research suggests that we're getting hungrier because we're getting fatter?

LUDWIGThat's, that's right. You know, for centuries, for millennia, humans have done a perfectly good job of controlling their weight without counting calories or without even understanding the concept of calories. In fact, most nutrition experts, people who do this as their day job, can't come within 200 or 300 calorie accuracy of understanding their daily balance. A difference of 300 calories a day, too much, would be the difference between being -- remaining lean and approaching obesity.

LUDWIGAnd, in fact, our brain has been programmed through evolution to regulate, to control our body weight just as it controls breathing and body temperature and a range of other biological functions. Something has happened in the environment recently, clearly this isn't our genes. It's happened too quickly. Some environmental exposure is causing that this highly-tuned system to be knocked out of balance. And we propose that it's all of the refined carbohydrates which raise insulin levels. And insulin is like fertilizer for fat cells.

LUDWIGWhen the fat cells start sucking in too many calories, the body has an energy crisis. And we can only respond by ultimately getting hungry and eating more. And unless we are extraordinarily disciplined it will become increasingly difficult to resist those biological needs over the long term.

NNAMDI800-433-8850 is our number if you have questions or comments. Have you tried to diet recently, primarily by cutting down on your calorie intake? How did you fare? And what did you find was the most challenging part of doing so? 800-433-8850. You can shoot us a Tweet @kojoshow or email to kojo@wamu.org or simply go to our website, kojoshow.org, join the conversation there.

NNAMDIJames Hamblin, the last time you joined us we talked about the addictive power of foods, whether Oreos really kind of maybe like crack cocaine. It seems that part of this conversation is about a habit many of us develop in thinking that all calories are just calories, regardless of their sources. There are a lot of people out there now saying, no, all calories are not created equal. What are they saying and why is this significant?

HAMBLINRight. Well, it, it goes right in line with what Dr. Ludwig is saying and it is that certain calories will cause fluctuations in the body's hormones and blood sugar levels, that will only augment future hunger. So you might be able to temporarily eat a low calorie diet of high, high sugar foods but it's going to be unsustainable, you're not gonna feel good. You're gonna feel, constantly, hungry. And after a few weeks, probably, go back to you're, to you're eating, eating more.

HAMBLINWhereas if you focus on eating a more balanced whole food diet, you will be able to sustain that for longer. And ultimately, you know, we're not proposing that this is overturning the first law of thermodynamics, you know, you will need to burn more calories then you consume. But it's about where you focus that, that intention of eating. And if you think about the calories, then, I think, you tend to make choices to say, well, I can only, I can only eat 200 calories now, I'd really like to get that as the, the most delicious 200 calories possible. I'm gonna eat 200 calories of ice cream or soda.

HAMBLINYou know, whereas if you think, you know, I just want to eat a good meal right now, something healthy and you chose fruits and vegetables and with less regard for the number of calories, you'll end up better off in the long run.

NNAMDITo what degree has the food industry helped to perpetuate this idea that calories are, well, just calories?

HAMBLINYeah, it's, it's so interesting. There's a new Coco-Cola commercial right now that shows people on a bicycle saying that it only takes, I think, it's 30 or 40 some minutes to burn as many calories as you get from a can of Coke, which sort of implies that it's just, they're all just calories. When really, those calories are going to lead to more hunger down the line and more fat deposition than calories from...

NNAMDISquash.

HAMBLIN...something better. Exactly, exactly. So they're not all the same but they're being marketed as, this is only this many calories and that's exactly as many calories as something else that's healthier.

LUDWIGYes. This is, of course, an argument the food industry loves because, by, by it, there are no bad foods. It's all calorie balance and the individual has total responsibility for maintaining that calorie balance. But lets take an analogy to another biological system, such as body temperature. Now, if you get an infection, you'll run a fever. So the body waits setpoint -- the body temperature setpoint, during fever, is being notched up. And so you can treat a fever by, say, getting into a bath of ice water, which will take heat out of your body.

LUDWIGBut how are you going to feel? First of all you'll feel rotten, you're gonna have an increasingly strong desire for warmer conditions and the body's also gonna fight back. It's gonna do that by causing you to shiver and constricting blood vessels, which are its way of desperately trying to warm back up to that higher setpoint. So, yes, you can think of fever as a problem with heat balance, you know, too much heat in and not enough heat out. It's not wrong but it's not very useful. So thinking about obesity as a problem of calories in and calories out, again, isn't wrong.

LUDWIGBut it's not something you can do much about. Alternatively by this new way of thinking, we would be less concerned with the calories in the food and how those foods are effecting our body weight setpoint, the tendency of the fat cells to suck in too many calories. By eating foods that are more natural, less processed, lowering in some levels, we can ratchet that body weight setpoint down. And then it's sort of like taking an aspirin for a fever. You know, you take it and then you naturally want, your body naturally wants to get rid of the extra heat. The same thing, we think, happens when you shift to a more natural, less processed diet.

NNAMDIAllow me to go to Mark in McLean, Va. Mark, you're on the air. Go ahead, please.

MARKHey, Kojo. I'm sorry that you got the background noise. But I wanted to speak about eating clean and sort of healthy eating, in the way that a body builder might eat. I'm currently on a diet, exercise campaign to drop a few pounds. And, you know, I'm eating healthy. I'm eating greens, dark greens. I'm eating fruits, I'm eating whole grains, I'm eating protein meat, chicken and fish. And I’m exercising. And I’m avoiding those types of calories that are just gonna result in additional weight gain.

MARKI've never been a big juice drinker or a soda drinker. I, I don't do ice cream. Those are like, you know, the anti-clean eating foods. So I wanted to ask your panel to comment about, as they have, to comment about eating clean, eating healthy in combination with exercise as an effective approach to weight loss.

NNAMDIJames Hamblin.

HAMBLINYeah, everything that you described sounds like you're on the right, right track there. And it, you know, not to over emphasize the role of diet, exercise is, obviously, something extremely important. I think it's just outside of the immediate scope of this conversation but that, that's certainly not to be downplayed, the importance of regular exercise.

NNAMDIGotta take a...

LUDWIG(unintelligible) ...

NNAMDI...oh, please, go ahead, David Ludwig.

LUDWIG...to that, yeah. I think, you know, some physical activity is great. I am a strong advocate of it. The, I think, the -- physical activity is, oftentimes, you know, very profoundly misunderstood in, in its role in weight management. You know, it takes -- to burn off the calories in one super-sized fast-food meal, it takes a full marathon to run. You know, we're much more efficient in holding onto calories than we are, you know, we can consume a tremendous amount quickly.

LUDWIGAnd the body, you know, through evolution, doesn't want to be wasteful with its calories. So when you're at extremely high levels of physical activity, you can begin to, you know, have a, you know, a very substantial impact on calorie balance. But for most people, physical activity has a whole nether role.

LUDWIGIt's not so much burning off calories as is, as is, it is in tuning up our metabolism, lowering insulin levels, promoting insulin sensitivity and helping, sort of, bring those fat cells back into line in behaving more cooperatively with the rest of the body. So physical activity is good if it's linked to a diet that lowers insulin levels and helps control hunger. But by itself, not a very good way to lose weight.

NNAMDIMark, thank you very much for your call. We're gonna take a short break. When we come back, we'll continue this conversation on The Science of Hunger. You can still call us, 800-433-8850. Where does calorie intake factor into the diet you follow? Have you been led to believe that all calories are just calories, 800-433-8850? I'm Kojo Nnamdi.

NNAMDIWe're discussing The Science of Hunger with James Hamblin, senior editor at the Atlantic. He's a doctor who writes about behavioral health, nutrition, culture and preventive medicine. David Ludwig is the director of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital. He's a professor of pediatrics at Harvard Medical School. We take your calls at 800-433-8850. David Ludwig, how would you say our diets have contributed to the biological factors that determine our body size and why does insulin have such an important role here?

LUDWIGRight. Well, you know, with the 1960s and 1970s, focus on reducing, initially, saturated fat, sudden we, the message generalized to reducing all kinds of fat. We launched this, probably largest, public health campaign ever to decrease the amount of fat in the diet. Remember our first food guide pyramid put all fats in the top and a whole range of processed starchy foods at the bottom. We were supposed to eat 11, six to 11 servings a day of grain products.

LUDWIGWell, these processed carbohydrates digest very quickly into sugar, metabolically they're very similar to sugar. They raise insulin -- blood glucose levels rapidly. And that causes, calorie for calorie, much more insulin to be produced than foods with, that are either more natural carbohydrates, like fruits or vegetables or proteins and fats. Insulin is a perfectly good and important hormone, critical to life. But its role -- it's key role is to regulate how much calories we store when there's too much insulin, for example, someone with diabetes getting too many insulin shots, they characteristically gain weight.

LUDWIGAnd conversely, if someone with type-1 diabetes doesn't get enough insulin, they lose weight. The problem, again, is that insulin is like a fertilizer for fat cells. And if we're eating foods that over-stimulate insulin, it can become exceedingly difficult to control calorie balance because the body gets programmed to calorie storage, weight gain mode.

NNAMDIJames Hamblin, you wrote for the Atlantic, recently, about sugar. And by the end of the piece, you get into how fast diet trends come and go, how often we're told one thing about our health that's displaced by another. When it comes to explaining the obesity epidemic, are we getting any closer to answering these big rhetorical questions?

HAMBLINI think we definitely are. And in that piece, I got into some, some differences of opinion that people have about which sugars might be healthier then, then others and, and how that opinion definitely, drastically shifts seemingly from, from year to year. And -- but now the consensus seems to be landing on that most of them, most are, of the caloric sweeteners are pretty much the same in terms of these metabolic health outcomes. And that they all need to be reduced. And that something like agave nectar is not going to allow, save you and allow you to, to use it as much as you like, as long as you replace that, replace your table sugar or high fructose corn syrup with that.

HAMBLINNow the differences are probably subtle and the better message is just to avoid them all, altogether. And that's a, that is a positive step toward addressing the epidemic as a whole.

NNAMDIYou also wrote, recently, about a doctor who was asked to study, from a scientific perspective, the effectiveness of pretty much every fat diet out there. What did they find and how do you think that squares with the kind of research that David Ludwig is doing?

HAMBLINYeah, that was Dr. David Katz at Yale and he, he does, he did a review of, of the literature out there. And the answer seems to be -- well, Michael Pollan put it, put it well a few years ago in a New York Times piece, eat, eat real food and not too much, mostly plants. And that's actually quoted in the, in the medical journal article that Dr. Katz wrote. And -- yeah, it's, it's sort of this real food being a way to, to guide you toward a proper diet.

NNAMDIGlad you mentioned real food because we got a Tweet from Steven, David Ludwig. Steven asks, "Can you ask your guests to define natural foods? What is, what is it about unnatural foods that makes them bad?"

LUDWIGRight. Well, you know, for -- since the dawn of our species before it until relatively recently, most of the foods that we are were close to natural form. Yes, you know, we've had food processing and technology beginning with stone tools and cooking hundreds of thousands of years ago. But the foods have largely been in natural form, which have calories together with a range of micro-nutrients and some vitamins, minerals, fiber, antioxidants. And because they're less processed, they take much of the digestive tracks to be digested.

LUDWIGAnd blood sugar and hormones rise a little bit after the meal and then come back gently. With massive processing, driven by the entices on commodities, which were, you know, the food policy has led to this as well as the enormous profitability of highly processed foods. You know, think of how much, you know, the industry can charge for an apple versus apple juice versus apple sauce versus sugar that's extracted from, from foods.

LUDWIGThink of the profitability. We now have a food supply that is predominately, extremely processed, enriched for calories, devoid of nutrients, digests too quickly and for many people, and there is variation from person to person, but for many people this over-taxes their body weight control systems. And inevitably leads to excessive hunger and weight gain.

NNAMDIAllow me to go to Matt in Chesapeake Beach, Md. Matt, you're on the air. Go ahead, please.

MATTGood afternoon. My, my question is this, earlier you had mentioned the, the refined carbohydrates. I'm wondering what some typical foods are that would have a higher count, in that regard. I'm also wondering if there is healthy foods or foods that are traditionally labeled as healthy foods, that are in fact more (unintelligible) the refined carbohydrates.

LUDWIGWell, you know, this -- like, like, just most of the center aisles of the supermarket are loaded with these foods. You know, perhaps the, you know, the, the granddaddy of them all was the low-fat Twinkie which took, you know, took -- admittedly took fat out of the Twinkie, replaced it with refined starch and sugar, more of them. And probably wound up with something even worse off, you know. And on top of that, these foods have health halos, so people think that they are somehow okay to eat.

LUDWIGAnd so that combination is focused on reducing dietary fat and replacing with starch and sugar, has not only, not helped us, but it, I think, has demonstrably contributed to the obesity epidemic.

NNAMDIThank you very much for your call, Matt. James Hamblin, in the end, does sugar deserve its reputation? There are people who have gone as far as to say, recently, that sugar is poison.

HAMBLINI, I think, that term is slightly hyperbolic, everything is poison in the right amount. And for some people who are dying of heart disease related to their diet, then there, there is certainly a case to be made for that. I, I don't know if it's helpful to go so far as to introduce that level of possibly panic or to focus simply on, on that message that might drive people away from eating natural sugars which are total normal and good for us. But there is definitely something to that idea.

NNAMDI'Cause the natural sugars are what we find in fruit, for instance.

HAMBLINExactly and, and no one is saying to stop eating fruit.

NNAMDIDavid Ludwig we're running...

LUDWIGIt's not really the, it's not really the sugar, I think, the emphasis on sugar can be a little misleading because fruits are among the healthiest thing we can eat except those sugars are in, sort of, meshed within the food structure, they're digested slowly. It's the rapid digestion and absorption that overwhelms the liver and the other hormonal systems from concentrated sugars you get from a sugary beverage or even from the, the rapid, the (word?) glucose from white bread. That's the problem.

NNAMDIWe're running out of time, David Ludwig, but you have noticed that existing research does not yet provide a definitive test for your hypothesis. What would provide such a test?

LUDWIGWell, many -- the problem with many of the big behavioral studies, is that they tell people to eat low fat or low carb. and then find that they don't weigh anything different after a couple of years. But if you look carefully, the people weren't really following those diets. So, you know, we wouldn't dismiss an a potentially effective cancer treatment if people didn't take it. So we need better quality studies. Feeding studies, for example, are more effective ways of helping people change their diet in an environment...

NNAMDIDavid...

LUDWIG...that tends to undermine our healthy eating...

NNAMDI...David Ludwig is the director of the New Balance Foundation Obesity Prevention Center at Boston's Children's Hospital. James Hamblin is a senior editor at the Atlantic. He is a doctor who writes about behavioral health, nutritional, culture and preventive medicine. Thank you both for joining us and thank you all for listening, I'm Kojo Nnamdi.

NNAMDIComing up tomorrow on "The Kojo Nnamdi Show," transforming buildings for a changing city, turning the old post office into a luxury hotel and the 11th Street bridge into a park. We look at adaptive reuse. Then at one, it's your turn to weigh in on the weeks headlines, the seismic shift in Virginia, rocking national politics, another high school shooting or flash floods in our region. "The Kojo Nnamdi Show," noon till two tomorrow on WAMU 88.5 and streaming at kojoshow.org.