Dr. Mark Hyman is a practicing family physician, medical advisor for Bill and Hillary Clinton, and a #1 New York Times bestselling author of multiple books on nutrition and wellness, including Eat Fat, Get Thin and The Blood Sugar Solution. Recently, he joined Dr. David Ludwig, endocrinologist and author of Always Hungry?, for a conversation that dispels traditional notions of how to lose weight. They discuss exciting new research and the powerful politics of food.
Dr. Hyman: You’re one of the few people in medicine or science who’s actually asking the hard questions, saying the hard things, and doing it in a way that it’s transforming health care. I’m really excited about your new book—I just stole a lot of your ideas from your research and I put it in my book–but I’m sure you did a better job. It’s about why we’re always hungry and what to do about it.
I want to start by having you talk about this idea that it’s not how much we’re eating that matters, it’s about what we’re eating. To shift perspective from the “how much”—which is what we’re all focused on, less calories—to the “what.” How did you come to that and how does that work?
Dr. Ludwig: I got my start in nutrition through the backdoor. I trained as a medical student, medical resident, pediatrics and endocrinology, never really taking much in the way of nutrition. As we know, that medical schools…
Dr. Hyman: Have none.
Dr. Ludwig: I think have all of four hours dedicated to nutrition in the curriculum, even though diet causes most chronic disease in this country. We spend a lot of time learning about drugs to treat those chronic conditions, not about diet. I began to think about nutrition from the perspective of an endocrinologist, meaning how does food affect our hormones, our metabolism, and the expression of our genes.
During the first few years of my career as a pediatric endocrinologist, I was using the standard treatments—a low calorie, low fat diet—to treat children and their parents in our clinic. While our studies in the basic laboratory were fascinating in revealing underlying biology, we seemed to be using the same approach that had been developed a century ago when bloodletting was still in fashion, which is focused on “calories in, calories out.”
Dr. Hyman: Eat less, exercise more, right?
Dr. Ludwig: Yeah, exactly. If that worked, we’d all be looking for something different to do during our days.
Dr. Hyman: You and I would have to find another job.
Dr. Ludwig: There’s abundant evidence that calorie restricted diets do not lead to long-term weight loss. If you’re interested in lowering calorie intake, you’ve got to love a low-fat diet. Fat has more than twice the calories per gram of protein or carbohydrate. It’s very tasty, very energy dense. If you pour olive oil onto a salad, or full-fat dairy products like cheese, you’re eating some of the highest calorie-dense imaginable foods, and yet time and again, low-fat diets have done less well than higher fat diets.
Dr. Hyman: So you’re saying it’s not a math problem.
Dr. Ludwig: People tend to overeat and become heavy because they’re hungry. That’s the main reason. There are other reasons, psychological factors or environment, but people overeat typically because they are hungry. And if you cut back on calories, what happens?
Dr. Hyman: You get hungry.
“And the more you cut back on calories, the hungrier you are, the slower your metabolism becomes, and the more you have to keep cutting back in order to maintain that degree of weight loss. That’s a battle between mind and metabolism that we’re destined to lose.”
Dr. Ludwig: You get hungrier. And your metabolic rate drops. You’ve got this untenable situation. Your willpower may say, “I’ve got a weight problem, I’ve got to cut back calories, and I’m going to stick to a diet.” You may have the best of intentions, but your body says, “Not so fast.” It’s going to start fighting. And the more you cut back on calories, the hungrier you are, the slower your metabolism becomes, and the more you have to keep cutting back in order to maintain that degree of weight loss. That’s a battle between mind and metabolism that we’re destined to lose.
Dr. Hyman: We’ve all been fed the idea that we should restrict calories to lose weight, and that all calories are the same so that it doesn’t matter where they come from as long as you eat less of them. But what you’re saying is that it actually slows your metabolism and makes you hungry, and you always fail. That just doesn’t sound like good news. You’ve done these studies to prove that you can shift your metabolism to actually being faster, being less hungry, and losing more weight, even eating the same calorie count.
Dr. Ludwig: “Are all calories alike?” is a very provocative question. How do you test that? We decided to ask, “Do the nature of the calories going in affect the number of the calories coming out?”
Dr. Hyman: What you’re saying is, if you eat different kinds of calories, will some burn faster or slower?
Dr. Ludwig: Can the kinds of calories you eat alter your metabolism in ways that science and medicine will see as relevant to the success of long-term weight loss? In the 2012 study we published, we took 21 young adults with high BMI who had been weight stable, brought their weight down by 10-15%, stabilized them at that new lower level, and then fed them one of three diets. That was randomized, so there’s no bias involved.
On one end, we have the conventional low-fat diet: 20% fat, 60% carbohydrate. The other end was the classic Atkins diet, with a whopping 60% fat. It would give a conventional nutritionist a nightmare. In the middle was the Mediterranean, we call it a low glycemic index diet. So we had 20% fat, 40% fat, and 60% fat.
Dr. Hyman: They were all the same calories, right? You just changed the ratios of protein, fat, and carbs, but the calories were the same.
Dr. Ludwig: Exactly.
Dr. Hyman: And you fed them the food. It wasn’t like, “Oh, just try to eat like this,” you actually gave them the food, which is a way better study.
Dr. Ludwig: Yeah. We fed them everything they ate, a seven-month protocol. During the key points where we collected the data, we admitted them to the hospital, so we could not only feed them, but we could keep them under 24 hour-a-day observation to prevent people from sneaking off and having a bacon double cheeseburger. We measured the total energy expenditure by something called stable isotopes. It’s very precise.
Dr. Hyman: It’s a way of double-checking on people.
Dr. Ludwig: We found that total energy expenditure, the total number of calories being burned, plummeted on the low-fat diet, as was expected. It dropped by more than 400 calories a day. It’s a big drop, so you’re going to be feeling cold, tired, and hungry. That’s going to be a bad predictor for weight gain. A low-carb diet saw no significant decline in energy expenditure at all.
Dr. Hyman: Low-carb, high fat.
Dr. Ludwig: Exactly, the Atkins-like diet had completely abolished this negative adaptation to weight loss. And the low glycemic index, Mediterranean diet, showed an intermediate value. That difference between the extreme diets was about 325 calories a day.
Dr. Hyman: Unbelievable.
Dr. Ludwig: That’s equal to the energy in an hour of moderately vigorous activity, without lifting a finger.
Dr. Hyman: So it’s like exercising without getting off the couch.
Dr. Ludwig: The study, at least in proof of principle, argues in a meaningful way that all calories are not alike to the body. The kind of calories going in alters the number going out, and the low-fat diet looked the worst.
Dr. Hyman: When these people had a slower metabolism by 300 calories a day, did it affect their weight?
Dr. Ludwig: We did it for just a month at a time, and we locked their calorie intake—it really wasn’t enough time to see their weight change. As expected, the weight started to drift. There was a little bit of a change in the expected direction in their body weight.
“It’s not your fault you’re fat. That’s a big myth. You’re fighting biology, and the answer is to get biology to work on your side.”
Dr. Hyman: But you wouldn’t expect that the low-carb, high-fat diet, they would actually lose more weight over time, even on the same calories.
Dr. Ludwig: This is a short-term study, but if that 325 calorie difference were permanent, that would be basically the whole obesity epidemic. If you translate those 325 calories a day into permanent weight change, you’re looking at about 30 pounds when you reach your new stable weight. That’s pretty much what the population has gained over the last 40 years.
Dr. Hyman: Unbelievable. Getting into the biology of obesity, it’s so profound to rethink the nature of why we get fat. An important question that nobody’s really asking is, “Why do we get fat, and how do we stop that inexorable slide into obesity?” When you talk about how fat affects us, what is actually happening to our hormones and metabolism? You saw this phenomenon, but can you explain it?
Dr. Ludwig: The premise of the book is a little provocative, which is that overeating doesn’t make you fat. Not over the long term.
Dr. Hyman: Of course overeating makes us fat, isn’t that what makes us fat? Tell us why that’s not true.
Dr. Ludwig: The process of getting fat makes us overeat. Something has triggered our fat cells to suck up and store too many calories, to hoard those calories, so there aren’t enough for the rest of the body. From that perspective it’s understandable what’s happening with hunger. The brain doesn’t realize that there are too many calories in fat cells. It just seems there’s too few in the blood stream for the brain itself, so it makes you hungry and begins to decrease metabolism to solve that problem. If the problem is not enough calories in the blood, and you just cut back on calories, you make things worse. So the question is what is triggering our fat cells to hoard too many calories?
Dr. Hyman: They just want to eat all the time.
Dr. Ludwig: They’re like unruly children who are hoarding all of the marbles for themselves and not sharing with the rest of the body.
The big problem here is the refined carbohydrates that have crept into our diet. Bread, pasta, cookies, crackers, low-fat Twinkies, sugary beverages. These raise insulin levels the most, and insulin is the ultimate fat cell fertilizer. This is Endocrinology 101. Someone with diabetes who gets too much insulin will gain weight, and someone with type 1 diabetes, they’re always losing weight. They’ll invariably lose weight even if they’re eating 10,000 calories a day. Without insulin you can’t store calories.
It’s not your fault you’re fat. That’s a big myth. You’re fighting biology, and the answer is to get biology to work on your side. Get the fat cells to open up, release their calories back into the body, you suddenly feel an intense sense of well-being. Hunger drops, cravings vanish, and we’ve looked at this in brain studies with magnetic resonance imaging, MRI. The cravings turn off.
“The ones who had the fast-acting sugar, their brain lit up like a Christmas tree. The addiction center just turned on.”
Dr. Hyman: So you can see it in your brain.
Dr. Ludwig: The area of the brain called the nucleus acumens is ground zero for addiction. In one meal of a fast-acting carbohydrate versus slow-acting carbohydrate, one lights up the nucleus acumens and the other doesn’t. It quiets it down.
Dr. Hyman: I call that your “trick milkshake study.” In this study, you took two identical looking and tasting milkshakes, one with a really fast-acting sugar carb, and one with a super slow-acting one, and you fed it to these overweight guys and looked at their brains under MRI. It was exactly the same calories, protein, fat, carbs, fiber, everything, so it couldn’t be like, “Oh, it stimulated their pleasure center because it tasted better.” The ones who had the fast-acting sugar, their brain lit up like a Christmas tree. The addiction center just turned on.
Then they were hungrier, and their blood levels with insulin and sugar were all higher, but it was the same exact calories and ratios.
Dr. Ludwig: You’re right. Same calories, protein, fat, carbohydrate, controlled for sweetness, and done in a blinded fashion so people didn’t know what they got. We did it double-blind so people couldn’t try to psyche it out, or placebo effect. If you think you’re getting something, it can affect brain function.
We saw, as expected, the blood sugar rose initially very fast, after the fast-acting carbohydrate. Insulin rose more, but then it bottomed out a few hours later. At four hours, people recorded feeling hungrier after the fast-acting milkshake. And then we looked at the brain.
Every subject responded the same way. Their nuclear acumens were more active after the fast-acting milkshake—we got very strong statistical significance. That was in the American Journal of Clinical Nutrition.
Dr. Hyman: It was a good article, and it underscored the powerful, addictive nature of sugar, right? It hit the same areas as cocaine or heroin.
Dr. Ludwig: I want to emphasize I don’t think this is unique to sugar. It relates to all fast-acting carbohydrates.
Dr. Hyman: So that could be bread.
“We need to move away from the ‘sugar bad, starch good’ model, because white bread raises blood sugar more than table sugar.”
Dr. Ludwig: People have been frequently focusing on fructose as the bad actor. In my view, pick your poison. Fast acting fructose can wipe out the liver, in high amounts, but has a very gentle effect on insulin. Fast acting glucose is okay on the liver at first, but it raises insulin levels the most, and that has an effect on the liver indirectly. I think we need to move away from the “sugar bad, starch good” model, because white bread raises blood sugar more than table sugar.
Dr. Hyman: Right, right. They’re both bad. The fat story also connects to the brain. Sugar lights it up, but how does fat turn it off?
Dr. Ludwig: In any nutrition study, we don’t know if it is the thing that you’re eating, or the thing that you’re not eating. Is it the fact that the fat is inherently good, or is it that when you’re eating more fat, you’re displacing refined carbohydrate? When we were told to focus on decreasing fat and saturated fat, we did. But we wound up not eating more fruits, vegetables, and legumes; we wound up eating more refined carbohydrates. Starch and sugar. Between white bread and butter, the bread is less helpful.
I’m not arguing that saturated fat is a health food, but it was overly demonized for the last 40 years, and had huge inadvertent consequences in altering people’s eating habits and driving the intake of processed carbohydrates. Is it the fat that’s doing something good, or the absence of the carbohydrates? And I think the last part is key, because when you eliminate the refined carbohydrate, your insulin levels plummet.
Dr. Hyman: When you eat sugar or refined carbs, insulin levels go up. Insulin drives that available fuel from the meal you just ate into your fat cells, right?
Dr. Ludwig: Yeah.
Dr. Hyman: You feel hungrier because all of the calories, fuel, fatty acids, and ketones are out of your blood, and your metabolism slows down because your body thinks you’re starving. Even though there’s so many calories stored in your fat cells, you’re hungrier, and so the whole thing just gets messed up. It’s a bad combo for losing weight.
Dr. Ludwig: Yes. Metabolic double whammy. Think about it this way. There’s been dozens of force-feeding studies, just as there have been starvation studies, done in controlled settings over the last 50 years or so. When people, regardless of their starting weight, are force-fed so that they gain 30 pounds, they’re miserable. They’re just as unhappy as the participants in the starvation studies. As soon as that force-feeding protocol ends, what happens? Their weight comes back down to where it started, or even overshoots. They wound up lighter than the people in the starvation studies.
That illustrates why overeating doesn’t really make us fat. Yes, you can gain or lose a few pounds by changing your calorie balance, but that only lasts until biology kicks in. Primal parts of the brain are designed to prevent us from becoming hypoglycemic and having too few calories.
When the brain perceives that, it activates primal mechanisms that go back hundreds of millions of years. We’re no match for that. We don’t have control over the total number of calories that we eat over the long term. We do have control over quality. When you change quality, calories follow.
Dr. Hyman: You mean you’ll eat fewer calories?
Dr. Ludwig: Ultimately you’ll either eat less, or your metabolism will not fall. Weight loss will be relatively faster in the combination of the two. But when your fat cells open up and release calories, you feel intense satiety.
Dr. Hyman: Which means you’re not hungry.
Dr. Ludwig: We’ve all felt satiety. It’s feeling like you ate too large of a Thanksgiving meal. You’re actively disinterested in food. Brain areas involved in hunger and cravings shut down, and you actually want to avoid food. That’s how people following weight loss surgery feel, and that’s why they lose weight for so long. We can bypass the bypass, by bypassing our highly processed diet.
“Why should it be so surprising that the quality of our foods would affect not just our bodies, but our emotions and our well-being?”
Dr. Hyman: Absolutely. Your book is full of these recipes that are creamy, satisfying, delicious, and I want you to tell everybody about the study you did.
Dr. Ludwig: Just to be clear, the pilot wasn’t research. We didn’t have a control group. We wanted to see the program that we had developed for the book. It’s a three-phase program with three weeks of meal plans and about 75 recipes. In addition to lowering refined carbohydrate, you want to look at other influences on the fat cell. Three key ones are stress reduction, quality sleep, and enjoyable physical activities. Not to burn off calories, but to improve insulin sensitivity and to keep your body from getting too sedentary. The program walks the reader through all of these systematically.
The first phase is 50% fat, 25% carbohydrate, 25% protein. It’s a very high fat, lush diet, full of rich sauces and spreads, nuts and nut butters, full fat dairy, avocado, dark chocolate, olive oil. That lowers insulin levels within a day or two. We did this pilot with volunteers from around the country, to fine-tune the program. Their stories appear throughout the book.
We got people throughout America, including Wal-Mart shoppers in Middle America who maybe aren’t as up on some of the higher fat alternatives. They’ve been following low fat diets and were frightened. They thought that, “If I eat these foods, I’m going to gain 20 pounds, not lose 20 pounds.”
Within a week or two, the foods that they depended upon—cookies, chips, crackers, sugary drinks—they not only weren’t attracted to them, but they found them unappealing. They would take a bite of a cookie and they would say, “Alright, what was the big deal?” That is not willpower, that’s something primal in the brain changing, and so our approach is really focused on molecular medicine.
Dr. Hyman: People panic when you say, “I want you to cut out sugar and refined carbs.” They panic and start negotiating, “Well can I have this, and can I have that,” and you know they’re addicted, right? And within days of jacking up the fat, all of it changes. People get freedom from this food prison that they’ve been in that they have no control over.
Dr. Ludwig: Yeah. Why should it be so surprising that the quality of our foods would affect not just our bodies, but our emotions and our well-being?
Dr. Hyman: You’ve been a huge voice in food policy. You use the science to show how stupid what we’re doing is, and you do it in a way that’s very polite, but it’s putting a dagger in the heart of the food industry and our policymakers. I’d like you to talk about the big ideas that could make a difference to change our food system and get rid of this obesity epidemic. How do you see us getting out of this?
“Every time we choose to eat something, we make a purchase; we’re committing a political act. And that act has implications, not just on our body, but on the food supply, on the behavior of corporations. We also have to start thinking of voting based on politicians’ policies around food.”
Dr. Ludwig: Well, why do we live in an environment where the healthy choice is the hardest? Why isn’t the healthy choice the least expensive, and the most convenient? This tends to degenerate into an argument between liberals who want government intervention and conservatives who think the government should just get off our back.
Dr. Hyman: No more nanny states, right? Nannies protect our children. I think that’s a good thing.
Dr. Ludwig: People argue we’re adults and we don’t need protection. The problem is the government is already in up to its ears in food policy. We don’t have a free market for food. The markets for all sorts of things are highly influenced by government regulations. We want that to be the case. Do you want the government to just say, “Listen, car safety is a matter of personal choice? We’re no longer going to enforce any regulations or rules around seat belts or standards.”
We would never think of doing that. And food is no different. The government is already involved in food policy through subsidies and supports. Even labor laws that allow fast food companies to pay their employees so little, and require them to, in effect, get subsidized by welfare, by SNAP, food stamps. We’re subsidizing fast food and junk food makers.
Dr. Hyman: And on the backend we have to pay for all the diseases they cause through Medicare and Medicaid.
Dr. Ludwig: We proposed recently in a piece in JAMA a small tax on all processed foods. Take all that money and subsidize whole foods. Since we eat more processed foods than whole foods, a small tax would lead to a massive reduction on the costs of fruits and vegetables, for example. We think that alone would have a massive impact on public health. But we all can vote with the fork as well as with the ballot.
Every time we choose to eat something, we make a purchase; we’re committing a political act. And that act has implications, not just on our body, but on the food supply, on the behavior of corporations. We also have to start thinking of voting based on politicians’ policies around food.
Why aren’t we hearing about this in the political debates? Politicians should be expected to lead. There is growing awareness. Little grass fires are alight around the country. We need to consolidate around a coordinated vision, and get out of this polarizing debate of whether we want the government to intervene or not, into how can the government, which is already involved, intervene in a way that aligns profit and public health.
Dr. Hyman: But the food industry is so tied in, the lobbying is so big, and they’re so intertwined in policymaking that our policies don’t match science, right?
“This is a $1 trillion dollar a year industry. There isn’t anything more political than food.”
Dr. Ludwig: Well another key part of this is campaign finance reform. The Center for Responsive Politics found that the food industry’s giving at least $50 million a year to politicians. Whose interests are they going to be representing?
Dr. Hyman: Monsanto gave $30 million just to defeat one proposition in California on GMO labeling. That’s just one policy. I’ve talked to Ann Veneman, who was the former Secretary of Agriculture under Bush, and I said, “Ann, how come the USDA, who does the food stamp program, spends $4 billion for soda for poor people, and on the back end have to pay Medicare and Medicaid? How come the USDA dietary guidelines recommend three glasses of milk a day,” which also is nonsense.
Dr. Ludwig: It’s okay to drink nonfat, sugary chocolate milk, but you can’t buy simple whole milk in schools. It’s not available.
Dr. Hyman: It’s so contradictory to science. And I said, “How come we can’t make science into policy?” She goes, “Mark,” she says, “The food industry has a lock on Congress and the White House.” I think that’s the challenge. I met with the Vice Chairman of Pepsi the other day. I had dinner with him, and I said, “Why are you using high fructose corn syrup in your soda? Why don’t you use sugar? It’s just better for you.”
“Mark,” he says, “We’re in business. The government is actually paying for us to use this by subsidizing it and making it cheaper. So yeah, I’m going to use it, because it’s cheaper. But like, I’m sorry. This is how it works.” That’s a scary statement coming from somebody like that. I think we have to, as a society, begin to take these issues on and take a stand.
Dr. Ludwig: This is a $1 trillion dollar a year industry. There isn’t anything more political than food. If we got 100,000 people to demand change throughout the country, that is going to have a massive effect. Vote with your fork and with the ballot.