Dr. David Ludwig is a renowned endocrinologist at Boston Children’s Hospital and professor of nutrition at Harvard School of Public Health. His most recent book, the #1 New York Times bestseller Always Hungry? offers a new way to look at health and fight obesity. In a Heleo Conversation hosted by Brian Johnson, entrepreneur and creator of PhilosophersNotes, Optimal Living 101, and en*theos, David discusses what so many dieticians got wrong in the 1970s-1990s and how we can use new research to live healthier lives.
Brian: Let’s start at the top. What led you to name the book Always Hungry?
David: In 2014, I had a provocative piece published in the journal JAMA that asked the organizing question: which comes first, overeating or obesity? We classically think that we overeat due to lack of willpower, that leads to weight gain and ultimately obesity and we just have to cut back calories.
We asked the opposite question: what if the body is being triggered to gain weight? We got this published and The New York Times took my first op-ed—I had some very nice academic sounding title. They changed it to something much better: “Always Hungry? Here’s Why.”
That really is the challenge, that people on a conventional low-calorie diet are always hungry. When you cut back calories you make that situation worse, and the conventional paradigm would have you just neglect that for the rest of your life. Ignore your hunger, eat less, and it’ll be fine. It’s not fine. Almost nobody can do it and even if you could that doesn’t say anything about what’s happening to your stress hormone levels, your body composition, the relative amount of lean and fat tissue. Yeah, if you can succeed in eating less over the long-term you’ll lose weight, but that doesn’t mean you’re going to do it in a healthy way.
Brian: Which leads us to one of the most important points of the book, which is a calorie does not equal a calorie.
David: We know that’s the case from many different lines of investigation. Just because there’s an association doesn’t mean that there’s a causality.
“It turns out that the delicious, high-fat foods we were told to banish from our plate by the first food pyramid greatly reduce risk for chronic diseases.”
The entire foundation of nutritional epidemiology is that all calories aren’t alike. When you eat more processed carbs, risk for diabetes, heart disease, cancer goes up. It turns out that the delicious, high-fat foods we were told to banish from our plate by the first food pyramid—nuts, olive oil, avocado, even real dark chocolate—greatly reduce risk for chronic diseases.
We know that from clinical trials. You could give people identical calories of fast-digesting carbohydrate versus slow-digesting carbohydrate. Those differences produced radically different changes in the body in the hours after eating. Hormones, metabolism, even the expression of genes throughout the body will differ, not just based on the number of calories you consume.
Brian: One of the studies that you conducted was with individuals who are given either corn sugar or cornstarch. The quality of the carbohydrate they consumed was different. You call it fast-acting or slow-acting. Can you talk about what that did metabolically?
David: The first set of studies have been looking at what happens with meals with identical calories—identical protein, fat, and carbohydrate—but varying the quality of the nutrients. Let’s take just carbohydrates. You can use high-glycemic index, a very fast digesting carbohydrate. Those are all the carbs that flooded our diet during the low-fat years. The low-fat diet that we were told to eat for 40 years had all these processed grain products at the base, plus more potatoes.
At the time, public health experts were saying, “sugar’s fine because it helps you eat less fat.” That’s the diet we ate.
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We found that after fast-acting carbohydrate is consumed, blood sugar shoots way up. That causes a massive outpouring of the hormone insulin. That insulin tells all of your organs and tissues to suck up calories. It says we’re going to feast, go to town. The problem is these fast-acting carbohydrates cause so much insulin to be produced that a few hours later we go from feast to famine. Blood sugar and the other calories in the blood plummet, so by three hours after the meal there aren’t enough calories.
The brain releases stress hormones that tell the body we’re in trouble and hunger goes up. We know that because people report more hunger when we give them a big plate of food; they eat more after the fast-acting carbohydrate. When we looked at the brain at four hours with something called functional MRI, we saw after the fast-acting carbohydrate this one area lit up, the nucleus accumbens. That’s the center of the dopamine pleasure and reward system, considered ground zero for the classic addictions: cocaine, heroin, alcoholism.
Brian: When you put the two together you’re in even more trouble.
David: That’s right. Plus stress hormones are going to try to suck calories out of storage wherever they can find them and, unfortunately, that includes muscle.
“Based on how calories affect our hormones and metabolism, the same number of calories can be doing very different things to our biochemistry, to our body, to our health.”
If that just happens once, it’s no big deal, but if you go through this cycle meal after meal, day after day, it could be eroding lean body tissue. During the surge of insulin, those calories get stored in fat, but during the crash too many calories get pulled out of lean tissue. At the same weight, you could have a much greater risk because you’re relatively more fat. That’s exactly what we saw in a study we gave rats for 16 weeks. Identical diets, again, just fast-acting versus slow-acting carbohydrate.
We controlled their weight so that both groups weighed the same. At the same weight, the group that got the fast-acting carbohydrate had 70% more fat and thus, since they weighed the same, much less lean tissue. Heart disease and diabetes risk factors were sky high. Based on how calories affect our hormones and metabolism, the same number of calories can be doing very different things to our biochemistry, to our body, to our health.
Brian: This has been one of the most challenging things to wrap my brain around. I thought fat made us fat and now it’s the processed carbohydrates making us fat.
David: The problem that people identified with fat in the 1970s, ‘80s, and ‘90s was based on this simplistic notion, that fat has twice the calories per bite of carbohydrate and protein. Calories are bad, so let’s get rid of fat and people will eat less and they’ll have an easier time maintaining a healthy body weight. Many researchers wrote that it was virtually impossible to become obese on a high-carbohydrate diet. That’s a terribly simplistic notion, because it takes out of the equation the other key point: how much satiety do those calories produce?
If you just think about energy density, the number of calories per bite, you’re considering the body like an inert storage tank, but we’re not. We’re a dynamic, biological system that responds differently to different calories. Fat has a lot of calories, but those calories can be intensely satiating. Do a little mind experiment. Consider eating 500 calories from bread, half a loaf, or from half a stick of butter.
Now first of all, which would be easier to do? A lot of people can eat six slices of bread. That happens when they bring the bread basket before a meal. Think about eating a half a stick of butter. Half a stick in you’re feeling pretty disgusting. Now what’s going to happen to those calories? That butter doesn’t raise your insulin. That fat is going to be hanging around your system for a long time. The bread shot your insulin sky high, so as soon as those calories came in they were being stored. Pretty soon you start crashing.
“The bottom-line is eating fat doesn’t make you fat. In fact, the fats that were banished in the first food guide pyramid are among the healthiest things we can possibly eat.”
Virtually every binge food has carbohydrate and many have zero fat, like popcorn, bread, fat-free Twinkies. Who binges on olive oil or butter? It doesn’t activate your nucleus accumbens. It doesn’t produce the reward. All of that is ignored in a simplistic calorie-count model. The bottom-line is eating fat doesn’t make you fat. In fact, the fats that were banished in the first food guide pyramid are among the healthiest things we can possibly eat.
Brian: So what are those healthiest fats?
David: Many foods with lots of saturated fat are perfectly healthy. Full-fat yogurt. Dark chocolate. The vast majority of calories from saturated fat look very good in clinical trials. There are no high added sugar foods that look healthy.
That doesn’t mean we want to be loading up on butter. We need a good distribution of fats, ranging from saturated fat in whole foods to monounsaturated fats which come from olive oil. If you’re eating olive oil, especially extra virgin, all that green color is phytonutrients, antioxidants, anti-inflammatory substances. Avocado and most nuts are monounsaturated.
Brian: Research shows compelling evidence about the efficacy, or lack thereof, of the low-fat approach?
David: For many years it was, “the only way to be less fat is eat less fat.” I think we can throw that out the window. The meta-analyses are quite clear that low-fat diets are the worst way to lose weight. Every comparison diet—be it low carbohydrate, Mediterranean—when you compare them fairly, the low-fat diet is inferior.
Then the argument became, all right, maybe you can lose more weight on a low-carb diet, but you’re going to be a good-looking corpse. Your cardiovascular disease risk factors are going to be sky-high. That’s where we can refer to three very big studies. First there was the Women’s Health Initiative which put 50,000 women onto a low-fat diet. They had 16 individual group sessions, lots of support. The control group just got written educational materials. Despite that imbalance, there was no benefit for any chronic disease, no lower heart disease, cancer, diabetes, nothing. It was a blowout.
The second study was Look AHEAD. This recruited people with type 2 diabetes for whom heart disease is the leading killer. Again they were put onto a low-fat diet. That study was closed early for futility, meaning that an initial analysis by independent statisticians showed not a hint of benefit for the low-fat diet.
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The third study was done in Spain. They had three groups. One high fat group got an ounce a day of nuts. A second group got a liter of olive oil a week per person. That should be a nightmare, from the low-fat scenario. It makes you fat, clogs up your arteries. The control group was a low-fat diet. The higher fat groups showed unexpectedly fast reductions in cardiovascular disease. The study was proven long before the expected end. It would have been unethical to keep the control group eating the low-fat diet.
These three studies put very substantial nails in the coffin of the low-fat diet. Does that mean that all low-fat diets are inherently bad? Of course not. Some populations around the world seem to be able to eat a low-fat diet, some quite healthy, which doesn’t mean that the healthy part of their diet is the low-fat component. If you took a low-fat diet and added nuts and olive oil maybe people would do even better.
In the United States, these blue zones are people who are highly physically active, have very high overall diet quality, low rates of obesity and insulin resistance. Most people in America are substantially overweight with high levels of insulin resistance. If somebody has insulin resistance that means they’re carbohydrate-intolerant essentially. It means that insulin can’t manage the influx of carbohydrates effectively, so much, much more insulin has to be produced.
What might work for Chinese peasants working 12 hours a day in the fields won’t necessarily work with Americans in the 21st century with rates of overweight and obesity at about 70%. As those Chinese peasants who were eating grain-based, low-fat diets moved to the cities, carrying their grain-based diet with them, but leaving their physical activity levels behind, their rates of obesity and diabetes are skyrocketing.
“We’ve been trying to tell the American public to eat more fruits and vegetables for years. That’s a tough sell.”
Brian: Even without emulating the Western diet.
David: What if America during the ‘70s, ‘80s, and ‘90s reduced fat, but replaced them with vegetables, whole fruits, legumes, minimally processed grains, what would have happened? Very likely the harm would have been much reduced and maybe there would have been benefits. We don’t know. That’s not what happened.
We’ve got to ask what is pragmatic. We’ve been trying to tell the American public to eat more fruits and vegetables for years. That’s a tough sell. Alternatively tell them to add back luscious, tasty, rich high-fat foods, olive oil, dark chocolate, avocado, full-fat dairy, that will be a much easier sell.
Brian: Can it be done?
David: It requires a change in mindset. The American public fears fat. According to a Gallup Poll, most Americans are still trying to reduce fat intake. In school, children can get sugary, non-fat milk called chocolate milk. They can’t get plain whole milk according to national policy.
We’re still stuck in a calorie in, calorie out, fat is bad, carb is good mindset and the first thing we have to do is change the mindset.
Brian: In terms of the low-fat chocolate milk kids get, you talk about the effects of our diet on our ability to focus. Eating what was recommended for 40 years by the food pyramid creates a lack of focus, and if persistent can look a lot like ADD.
David: If you were a 10-year-old boy who ate the bagel, fat-free cream cheese and glass of orange juice your mother gave you because she thought that was healthy, because that’s what was told to us, and now your blood sugar is crashing at 10:30 in the morning as you’re sitting in social studies class, your adrenaline levels are skyrocketing—is that 10-year-old boy going to be sitting politely, focused, paying attention and listening? Or is he going to be distracted and shooting spitballs at the girl next to him? What diagnosis is the teacher going to think that boy has? ADD.
Interestingly, what is the treatment that we use for ADD? Amphetamine, Ritalin. These are all analogues of adrenaline, epinephrine. They have very similar properties, are stimulants. Interesting that the body is responding to hyperglycemia with a surge of adrenaline and yet we find that we can treat those symptoms by giving stimulants. Why is it so surprising that a highly processed diet would affect the brain, not just the body?
Brian: Then you extend that to the 30-year-old version of that 10-year-old, and there’s the same issues of inability to focus and that stress response is going to be persistent.
David: Brain fog. The brain is susceptible to inflammation. With insulin resistance and a poor quality diet, chronic inflammation develops in the body and that can spread to the brain. Once the brain gets inflamed you’re in real trouble.
“This whole calorie counting notion is a delusion. Nobody can do it.”
Brian: We talked about different theoretical perspectives in the research. Can you talk to us about the practical side of it?
David: This is targeted for America, where most people are at least a little overweight. Phase 1 asks you to eliminate whole grains, potatoes, and added sugar. It’s just 2 weeks, and you replace those with these luscious high-fat foods, nuts, nut butters, full-fat dairy, olive oil, rich sauces and spreads and you can have real dark chocolate. Because you’re using high-fat foods to displace the processed carbohydrates, you don’t miss them.
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In fact, we encourage people to eat as much to feel satisfied, snack when hungry, and never count calories again. This whole calorie counting notion is a delusion. Nobody can do it. It’s quite clear that not even a trained nutrition expert can get their calorie balance to within 350 a day. If you were off by 350 calories a day, you’d go from normal weight to massive obesity in just a few years. It begs the question, how did humans ever manage to maintain a healthy body weight before the very concept of the calorie was invented 100 years ago? You don’t need the conscious brain to control calories. We have a hypothalamus, we have brain systems that have evolved over hundreds of millions of years. If we give them half a chance, that controls our body weight perfectly well by adjusting hunger and our metabolic rate.
Phase 1 is designed to jumpstart this metabolic change, lower insulin, calm chronic inflammation. Then phase 2 we add back minimally processed whole kernel grains, like steel-cut oats, buckwheat, quinoa, brown rice. We bring the total fat down just a little, so from 50% to 40%. Then you stay in phase 2 as your weight comes down to its new lower set point. That is quick for some people, slow for others. We don’t want you to try to consciously control it. You give the body what it needs and it figures out the rate of weight loss that works for you.
“We want maximum benefit for minimum deprivation. We don’t want to come up with these arbitrary principles and expect everybody to live by it.”
Then, after your weight stabilizes at this lower set point, you go into phase 3, where you begin to mindfully explore having just a bit of processed carbs. Some people can handle a little pastry once in awhile, some ice cream at a party. Why not? We want maximum benefit for minimum deprivation. We don’t want to come up with these arbitrary principles and expect everybody to live by it. If you can tolerate it, great, add it back until your tipping point.
We give you symptom checkers to show you where that tipping point is. Once you find it, you just back off. For most people, the benefits of being in control of their hunger, feeling good, enjoying a healthy weight, are much greater than fleeting pleasures of processed carbs. Once people have experienced this we find that it’s very easy to self-adjust in phase 3.
The focus is on food, but we also bring in three life supports: physical activity, stress relief, and quality sleep. These three things synergize with diet to produce maximum, internal metabolic health.
Brian: You’ve got my almost four-year-old son asking for a passeggiata after dinner.
David: The passeggiata is the Italian walk after dinner—they don’t put on spandex and heart rate monitors. They’re going out, enjoying the last rays of the sun, socializing, and that physical activity is helping their glucose tolerance after the meal. They’re reducing stress, preparing themselves for sleep. We don’t have to be constantly on treadmills. Some people need a really vigorous workout, but for other people, we can bring enjoyment back into physical activities. You don’t have to deprive yourself of calories and ease in these modern, aerobics-focused, physical activity programs.
Brian: Perhaps even more importantly, enjoyment.
David: Exactly, they’re focused on the enjoyment as opposed to deprivation. When you line up biology with behavior then you get benefits as you enjoy yourself. Weight loss does not have to involve suffering and deprivation.
Brian: One final question: what would the one tip be that you would share with someone passionate about optimizing their lives and actualizing their potential?
David: Forget calories, focus on quality, and let your body do the rest.