Dave Asprey and Dr. David Ludwig Talk Hunger, Food Politics, and the Failure of the Calorie Balance Model

“We really agree that the calorie balance model works well if you’re a toaster oven. But humans aren’t machines.”

Ever wished you could rewire the way your body works? Fiddle with the controls a bit here and there and get rid of cravings, unexplained weight gain, low energy levels? Dave Asprey, author of the New York Times bestseller The Bulletproof Diet, and Dr. David Ludwig, renowned endocrinologist and Harvard professor, both set out to do just that. After years of researching why our diet impacts our body the way it does, Dr. Ludwig wrote Always Hungry? Conquer Cravings, Retrain Your Fat Cells, and Lose Weight Permanently. Asprey’s approach was a bit more personal – he undertook a major weight-loss journey, and along the way, sought out ways to “hack” his health.

When Asprey and Dr. Ludwig sat down to talk about Always Hungry?, the two experts explained why the big claims in the title, including permanent weight loss and abolishing cravings, aren’t too good to be true. In fact, they’re more attainable than you might think.

Dave Asprey: It’s not so common to find people who are practicing full medical work and researching nutrition. It’s a very useful combination but it’s unusual. How did you get there?

David Ludwig: I’ve always been very sensitive and aware of food, although I was raised in the 60s and 70s when diets weren’t as bad as they are today. But after school the ice cream truck would come along and we were already getting candies and sweets that had long lists of artificial ingredients. I ate them like everybody else, but I never felt really good about that.

I also come from a very politically active family. Some of my earliest recollections are being taken to civil rights demonstrations and to war protests. I became very politically aware, and I got interested in science and medicine. All of these interests converged after I finished my training as an endocrinologist, because it turns out that food has fundamental relevance to our biology.

It’s a highly political issue. Every time we eat we are making a powerful political statement to the food industry as to what we want and what we don’t. I’ve found that my day job can include both clinical medicine, seeing patients, and still be relevant to nutrition and health, research, politics and public health advocacy. An advocate has to actually be able to pronounce the word.

As an endocrinologist, I became interested in how food affects our hormones, which are powerful. Every time we eat, hormones, not just insulin but dozens of other hormones and related substances change in profoundly different ways. These hormones in turn alter our metabolism and literally the expression of our genes. The notion of food as medicine is quite literally true because virtually every pathway that exists in the body that can be exploited for drugs was there originally in a direct or indirect fashion to integrate food with our physiology.

Dave: That really does blur the line between food and drugs, doesn’t it?

David: We can use food as a drug for better and for worse. Hunger and cravings are a really difficult combination to fight. The food industry would like to say it’s all our personal responsibility to just control our calorie balance, there are no bad foods, but there’s quite a strong line of investigation to suggest that certain foods profoundly undermine our metabolism in ways that are not all that different than certain classic drugs of addiction.

Dave: My favorite processed food marketing slogan ever is, “You can’t eat just one.” You fire up that part of the brain and you’re going to have that drug-like response, “I’ve got to eat the whole bag of potato chips, not just one.” You found in your study exactly which part of the brain is contributing to that even in the absence of the blood sugar crash, because you’re talking about a brain craving that’s dopamine based. It’s a neurotransmitter, not just a glucose thing.

Overeating doesn’t make you fat. The process of getting fat makes you overeat.

David: The brain is critically dependent upon calories. A brief interruption would lead to loss of consciousness, coma, seizure, and death. When blood sugar drops the brain does something, which makes perfect sense from an evolutionary perspective.

First, it makes us hungry. Second, it starts activating craving centers so our ability to say “no” vanishes. After that, emergency stress hormones that drag calories out of storage sites start to be secreted. This will temporarily solve the problem, but it does so causing great stress to the body. If that continues–these swings in calorie levels and hormones–then metabolism will actually slow down.

All calories aren’t alike metabolically and if you simply focus on calorie restriction with the wrong foods you’re setting up a battle between mind and metabolism that you’re likely doomed to lose.

The main premise of my book is simple. Overeating doesn’t make you fat. The process of getting fat makes you overeat.

That sounds provocative but there’s actually a century of research involving literally thousands of articles that support the argument that body weight is controlled more by our biology than our will power.

Let’s say you’re doing a nutrition study with human participants. You put them on starvation rations for a few weeks. They’re going to lose weight of course. That’s the law of physics.

But what’s going to happen next, they’re going to get very hungry and their energy expenditure, the calories they burn off, is going to plummet because the body fights back increasingly aggressively against the calorie restriction. Once the people end the study, their weight comes right back up to where it started, typically even a little higher.

The opposite is also true. There’ve been dozens of overfeeding studies where participants are brought into a research unit, locked down, and then basically forced to eat very high calorie diets. Again, of course they gained weight. That’s physics. What also happens is they lose all interest in food. They feel very uncomfortable and their metabolism speeds up in an attempt to shed these extra calories. The participants are as unhappy in overfeeding studies as they are in underfeeding studies, because the body has a certain weight it wants to be.

What we recommend is turning dieting on its head. We suggest you forget calories. Calories are not a very useful notion. First of all, not even the world’s most trained dietician could guess calorie balance to within 350 a day accurately. If you are off just by 350 calories between intake and expenditure a day, that would mean the difference between remaining lean or becoming massively obese in about five years.

The only way to lose weight permanently is to shift metabolism, to retrain fat cells to open up. The problem with the modern American diet is, especially with all the processed carbohydrate, it increases insulin levels and chronic inflammation. Those force fat cells into a feeding frenzy. They suck up too many calories leaving too few for the rest of the body. That’s why we get hungry, that’s why we get tired. Just cutting calories makes that situation worse. It doesn’t address the fundamental problem, which is that the fat cells have been on calorie storage overdrive.

Certainly if you just don’t get enough calories the body is going to fight back. The problem in America isn’t that we’re not getting enough. We’re obviously getting too much. But they’re not staying in our bloodstream.

Even though we think of obesity as a state of excess, it’s physiologically more akin to a state of starvation. The rest of the body is starving because fat cells are hoarding more than their fair share of calories. You can’t solve that problem by cutting back calories. The only way to do that is to change what you’re eating in order to lower insulin and calm chronic inflammation.

Dave:  Have you ever been fat?

David: I was lean and athletic through my adolescence and 20s. I went to medical school just a little bit later because I had taken off some time, travelled a bit. I started to notice in my late 20s, early 30s that I’d been putting on a pound or two a year. For the first few years it didn’t much matter because I started out pretty lean, I just got an extra larger pant size or two. But then it kept going. By this point I’d already gotten interested in obesity research, although I was more focused doing genetic studies. I reached the BMI of 25. I had a little bit of an identity crisis. “I’m an obesity researcher and I’m about to cross the threshold into overweight.”

Fortunately, just at that time I came across new theories of carbohydrate including this notion of glycemic index, how carbohydrates digest and affect our hormones. I spent a few months buried in Harvard’s medical library. I found articles that dated back in some cases to the 1800s. I just absorbed it all. I put together theories that had been out there in my own way. I’m not suggesting that this is by any means all my creation. This is building on research that has been around for decades, if not a century.

Then I designed experiments to do in the laboratory, and I also did an n-of-one experiment on myself. I increased the fat content. I’d always eaten pretty healthy from a standard perspective, but I’d eaten a lot of whole grains and not too much sugar. It was a pretty high carbohydrate diet, so I greatly increased fat. I cut back on the refined carbs, I increased protein a bit, and made no attempt at all to lose weight. Three months later I dropped 20 pounds and three waist sizes.

We did a national pilot of the book’s program with over a couple of hundred people for 16 weeks. Most people report the same thing, that before the first pound was shed they experienced the cravings just seem to vanish. Just like that study, the brain imaging, it’s like a metabolic switch is being flipped. Cravings turn off.

Dave: I have learned when I was obese to value the feeling of hunger, like, “Wow, I’m really hungry, that makes me a good person,” which actually it doesn’t. You’re not nice when you’re hungry. It’s really a self-destructive state, [this idea that through] self-denial you’re supposed to somehow be helping your biology. It turns out you’re not helping your biology, you’re not helping your hormones, and you’re burning huge amounts of energy fighting off cravings, and you lose eventually anyway and then you feel like a failure.

I think we need more words for hunger.

What I came to believe is that hunger is a powerful signal from your body that you’re doing something wrong. You should eat the right stuff, and when you do that your hunger should go away for a long period of time. If the hunger comes back quickly then you didn’t eat enough, or you didn’t eat the right stuff. That hunger’s really, really useful but it’s not something to treasure because it’s going to make you thinner. That kind of thinness comes at huge cost biologically and energetically or emotionally.

David: I completely agree with you. We have a five-hour rule. If you eat a meal and you’re feeling not over stuffed initially but then not famished several hours later, if your energy remains good, your mental clarity remains good, then you ate the right amount and the right type of food. If not, you’re learning, it’s just an experiment. You’re the biohacker, so there’s opportunity to revise.

One other thing I wanted to add. I don’t know if this is true but I heard that the Native Americans have 20 names for corn because it was so important to certain Native American societies that were agricultural, and the Inuits in the north had 20 names for snow, all these different subtle gradations. I think we need more words for hunger. Hunger isn’t all the same thing. There’s a hunger where you’re desperately hungry, you’re craving, your energy is crashing, you feel a basic instability in your core. That’s because primal brain areas are being threatened by lack of calories in your bloodstream.

There’s another kind of hunger which you get after eating just right for lunch and then dinner rolls along and you feel this stimulating interest in food. It’s not bringing you down and making you desperate. It’s actually waking you up and creating an appetite for good food. Those are profoundly different states. One is a state of good metabolic functioning and your brain’s saying, “You know what, now is the time to recharge.” The other is saying, “You know what, we’ve got a medical emergency going.”

Dave: Those are fundamentally different states. I never knew that there was the “I could eat” state. The most powerful hunger suppressant for breakfast I know of is unquestionably Bulletproof Coffee and there’s a fat signaling thing in there. If I do that, when lunch time rolls around I get this kind of like, “You know, I could eat.” Like it’s one in the afternoon or something, I don’t have to, I’m not going to die if I don’t eat. I just, I could eat and I’m going to feel good if I eat.

I had never experienced that in my life as a former obese person because every meal was like, “Okay, I think I can make it or maybe I’ll just have three peanut M&Ms or whatever it is, I just have to have something.” I don’t think I ever experienced that until sometime after the age of 30.

What about snacking? If you need to snack does it mean that you failed?

David: Snacking is totally great, especially in the beginning of a new diet or weight change. Calories should never be the focus, but we all have different calorie requirements. The question is who’s in control of the calorie balance? Is it our bodies or is it a diet doctor?

I argue it should be our bodies. It may take a while to figure out how much food you need and how you match your food amount to different stages of weight loss. During the active stage of weight loss your body is burning storage fat. That rate of weight loss and fat burning will change through different stages of the diet and so your needs are going to change. In addition, physical activity level is going to change your needs.

Hunger, cravings, energy level, general sense of well-being, and duration of satiety — these five symptoms change in coordination with what you’re eating. You want to study them to come up with an integrated picture of how what you’re eating is actually affecting you.

Dave: When I first started noticing changes in my energy, I began taking notes. In the margins of my notebook, I’d write, “Energy crash two o’clock. What did I have for lunch?” and I’d write it down. I did this for a long time until I had built this awareness of what was causing these. They’re not random, and they’re not just a personal failing. It was an energy failing.

I was trying to figure out why I didn’t gain weight when I cranked up the butter in my Bulletproof Coffee. At one time I was doing between 4,000 and 4,500 calories a day and my plan was to overfeed and to maybe gain three pounds when the math said I should gain 20 pounds.

We really agree that the calorie balance model works well if you’re a toaster oven. But humans aren’t machines.

But I was eating very, very low carbohydrates, tons of Bulletproof Coffee and tons of steak and tons of vegetables, but not starchy vegetables, and I ended up losing weight on that number of calories. It was like, “Okay, what’s going on?”

As I’m digging in on all this, I found a metric from the agriculture industry, the feedlot industry. They have a metric called feed efficiency. They found that by administering antibiotics they had a 30% change in feed efficiency; that means on exactly the same number of calories the cows got 30% fatter when they had tiny amounts of these drugs. Doesn’t the existence of that kind of violate this physics of calories in, calories out?

David: We really agree that the calorie balance model works well if you’re a toaster oven. But humans aren’t machines. What happens is that we adapt to changes in calories. When calories go down, our metabolism slows and when they go up our metabolism speeds up. We adapt to it. We’re not even getting into perhaps an even more interesting question, what happens to body composition? We did a study with rodents. I don’t like to do a lot of animal studies, but it’s hard to control people’s lifestyles totally. You can’t just lock them up for six months.

We gave these rodents the same proteins, fats, and carbohydrates, one fast acting carbs, the other slow acting carbs, in both cases starches, just fast digesting starches, slow digesting starch. We found that the animals eating the fast digestive starch started gaining weight excessively. So we did what you’re supposed to do according to the calorie balance model, which is cut back calories. We did that and we kept the weight gain of the two groups the same. The fast acting carb group gained the same amount of weight with fewer calories, which means that its metabolism was slowing down.

Then at the end of the study we analyzed body composition. We used something called tritiated water. It’s an isotope that goes through aqueous water but not fat. We found that at the same weight the animals that had the fast acting carb had 70% more fat.

Guess what you have less of? Muscle. This is what has been called TOFI, thin outside fat inside.

Dave: Oh, the “skinny fat” thing.

David: That’s right. Even if you have a normal BMI you may be at major risk for weight-related complications because of your body composition and your metabolism. This is another way. When we eat calories, do those calories wind up going to muscle and being oxidized? They get oxidized or burned because you’re going to be feeling energetic. Even if you don’t work out and get on the Stairmaster you’re going to be fidgeting, you’re going to want to burn off those calories. Or are those calories being directed to fat cells, and are they serving only to cause more obesity, more fat development? That’s a really key thing.

None of this is explained by the calorie balance model. It has to do with the metabolic effects of calories. The chief culprit here is the refined carbohydrates. Beyond that we want to get the balance of protein, fat, and carbohydrate right, and then we want to bring in some lifestyle supports because other things besides diet affects fat cells: stress, sleep deprivation, and being too sedentary. I don’t mean not getting on a Stairmaster. I just mean spending too much time sitting. We want to get people engaged in enjoyable physical activities, not to burn off calories but to tone their metabolism.

I actually have a section in the book that reviews this, why exercise doesn’t cause weight loss. Exercise is good but for a lot of reasons but short of marathon level, weight loss just isn’t one of the benefits. That’s because when you work out you burn off more calories but then you tend to compensate.

Our activity level, like our appetite, may be regulated by parts of our brain. The only way around that is to shift the set point, not by just burning off calories and sticking to the same diet. You have to alter what you eat and these other lifestyle influences on fat cells.

It’s not your fault you’re fat. That’s not a message that you’ll ever hear from the food industry, because they want to blame the problem on you and not the massive infusion of industrial processed foods into the American diet.

Dave: I grew up thinking, “Well, jeez, if I just can exercise an hour and a half a day six days a week, I’ll finally lose this weight,” and it never worked and it made me so mad. “And if I go on a low fat diet it’s going work.” You could lose 20 pounds and gain 30, and lose 30 and gain 40, and all that.

David: Just think of the human toll that this calorie balance model has taken on us psychologically. If all calories are alike then it’s your fault you’re fat, for not being able to control your calorie balance.

We have to reverse the psychological toll taken on people from the calorie balance model. It’s not your fault you’re fat. That’s not a message that you’ll ever hear from the food industry, because they want to blame the problem on you and not the massive infusion of industrial processed foods into the American diet. If you are eating these foods, you’re going to be programed biologically to gain weight.

Dave: The food industry needs disrupting because it’s broken. That’s one of the things I’m here to do. I architected the Bulletproof Bar, these protein bars. We have a collagen protein and tons of Brain Octane. I got tired of eating things that made me hungry so I engineered something that is designed to not make me feel hungry. In fact, I’m looking at putting a money back guarantee on them right now and saying, “All right, eat this and if you’re still hungry two hours later, either you just ran a marathon or there’s something else going on,” because it doesn’t happen.

That’s the exact opposite of what a food company does if they want to make money. Because a food company, okay, here’s a 100 calorie, high-glycemic bar. You eat that. You’ll eat another one an hour later and another one an hour later. But if you make a bar that feeds someone for a long period of time then you sell a lot less. It changes the whole economics of the food industry if you sell food that makes you full versus food that makes you hungry.

David: We need to consider our diet and our health as matters of national security. If we don’t do something about diet and obesity related diseases, we’re looking at massively increasing budget deficits, which I argue is contributing to the political polarization in Washington. Democrats and Republicans are fighting because there’s less and less discretionary spending. All those resources are being siphoned off into diet related disease, and that we really have to become all advocates and activists voting with the ballot and also voting with the fork.

Eating well is a radical political act. We transform our health. We become role models. We influence the food supply.

This conversation has been edited and condensed.