Dr. David Ludwig is a practicing endocrinologist at Boston Children’s Hospital, professor of nutrition at Harvard Medical School, and author of the New York Times #1 bestselling book, Always Hungry? Recently, he joined Dr. Christiane Northrup, women’s health advocate and bestselling author of Women’s Bodies, Women’s Wisdom and Goddesses Never Age, for a Heleo Conversation on why a healthy diet isn’t based on deprivation, why the weight-loss advice of the last several decades hasn’t worked for most Americans, and how to begin building a more sustainable lifestyle. This conversation originally appeared on Dr. Northrup’s podcast, Flourish! It has been edited and condensed.
Christiane: Recently, I have been listening to Jason Fung’s podcast. He’s a nephrologist in Toronto who treats end stage kidney disease with dialysis, and he recommends therapeutic fasting. I have always been under the impression that fasting lowers the metabolic rate and leads to the loss of muscle. Dr. Fung said this is not true at all. He cites studies that show fasting increases the metabolic rate by 13% and does not cause loss of muscle whatsoever. Can you speak to that?
David: Fasting is a double-edged sword. It’s a very powerful technique if done the right way, but very often it is done the wrong way. People intuitively understand if they just stop eating for a day they get very hungry. It’s exceedingly difficult for many people to fast even 12 hours, to go without having a bedtime snack and then something very sugary and processed in the morning.
The key to understanding fasting is the metabolic state we are in when we begin the fast. For most people who are eating a carbohydrate-heavy diet, it’s low quality. Insulin levels are high in the body. What insulin does is program your fat cells to store calories, and inhibits those fat cells from releasing calories back into the body as effectively as needed when we stop eating. That’s why people get hungry again two or three hours after a meal. How do we expect people to fast when their body is in that metabolic state?
If you try to cut back calories or fast, and your body is not metabolically prepared for it, you go into a starvation response. The metabolic rate will slow down if you enter fasting that way, and your body creates stress hormones like cortisol, which work to drag calories out of storage, but the wrong calories. You don’t want calories coming out of your muscle and lean tissue. You want them coming out of fat cells.
How do we do this? Fasting can be very effective if we are fat-adapting. That means our fat cells have been trained to release their calories on demand. The best way to do that is by first improving the quality of what we eat, cutting down on the processed carbs, eating a lot of healthy fats, the right amounts of protein. Insulin levels drop and then the fat cells become adapted. You can move from feeding to fasting in a much less stressful way and, in that state, intermittent fasting can help some people take good results to the next level.
“Our body rebels against deprivation. If you just cut back calories, your body is going to fight back.”
Christiane: That makes so much sense when you think about where the vast majority of people are. Just going into a fast would be very, very stressful. In your program, there is a kind of induction phase. The first two weeks, it’s no added sweeteners of any kind, because you want to reset your taste buds and sometimes just the sweet taste might trigger an insulin response. Do you want to speak to that?
David: Sure, we know there are sweetness receptors throughout the gastrointestinal tract and also in fat cells. Some of the artificial sweeteners we consume will be stimulating not just the experience of sweetness in the mouth, but will stimulate receptors elsewhere in the body. That can have metabolic effects, including raising insulin, the granddaddy of all fat storage hormones.
Preliminary studies suggest you can get concentrations of some of these artificial sweeteners—like if you’re drinking three, four diet colas a day—you could get concentrations in your bloodstream that will activate those taste buds on fat cells. If those get activated, you are doing exactly the opposite of what you want to do.
Yes, if you are drinking three or four sugary beverages and you switch to artificially sweetened beverages, you are going to do your body a favor. But that’s not the full question. It’s what happens with those artificial sweeteners compared to unsweetened or natural kinds of beverages. You limit the results you can get, both for metabolic reasons but also because you are continuing to program your neurobiology, that connection between your mouth, your brain, and your behavior, to crave these hyper-sweetened foods, and inhibiting your ability to appreciate the natural sweetness of fruits and other food that may not be sweet at all.
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Christiane: I remember when I began to add food [back to my diet], suddenly, an apple or berries with no sweetener were exceedingly sweet. I would ask everyone who wants to improve their metabolic rate just remove all added sweeteners of any kind for two weeks and you will indeed not only reset your taste buds but reset the gut sweet receptors and the taste buds on fat.
David: This is key. Our body rebels against deprivation. If you just cut back calories, your body is going to fight back. You will lose a few pounds. That’s just the law of physics, but humans are not inanimate objects. When we cut back calories or just remove sugar, either biologically or psychologically you are going to feel a sense of deprivation, so you have to replace it with something.
“We think of obesity as a state of excess, too much, so just eat less, force yourself to move more. That creates more deprivation. In fact, obesity is really a state of starvation. The fat cells are feasting, but the rest of the body is actually starving.”
The key is to help you get rid of not just sugar but the whole range of processed carbs that flooded our diet during the low-fat years: bread, rice, potato products, cookies, low-fat chips, crackers, the fat-free Twinkie. To get rid of those we have to increase the fat in our diet. Many of these fats, as every cook knows, are luscious and tasty: olive oil, avocado, nuts and nut butters, rich sauces and spreads, full-fat dairy, even real dark chocolate.
You let some of these fats that were banished from our plate back into the diet and they help you get rid of these processed carbohydrates without missing them, so you don’t have to suffer deprivation.
We think of obesity as a state of excess, too much, so just eat less, force yourself to move more. That creates more deprivation. In fact, obesity is really a state of starvation. The fat cells are on calorie storage overdrive. They are feasting, but the rest of the body is actually starving. There are not enough calories to feed the brain consistently, to feed the liver and the muscles and the kidney. That’s why we get hungry and that’s why metabolism crashes on a low-calorie diet.
We have to treat the source of the problem. Just cutting back calories or fasting if we are not prepared for it is symptomatic treatment. The source of the problem is these fat cells on calorie storage overdrive, mostly by insulin. Once we treat that, these fat cells open up, the calories flood back into the body and you don’t have to force deprivation. You can allow your body to shed those extra pounds without worsening the problem by adding deprivation to it.
Christiane: One of the things you have pointed out, is this thing we have all been told and that many healthcare practitioners are still telling people: “decrease your calories, increase your activity.” It’s just wrong. Then of course, we blame the person for regaining the weight. It also creates a broken metabolism. And every time you do this—I have been doing this since I was 12—your metabolic rate decreases. Can you talk about that and how to fix the broken metabolism?
David: The calorie in-calorie out model that considers all calories alike says it’s ultimately a question of willpower. Eat less, move more, you will lose weight and that will take care of the problem. So many people struggling with their weight have heard their doctors, nutritionists, well-meaning people, friends, and family suggest that.
Here’s the problem with that. As you said, first, it does not work. Less than 10% of the U.S. population who are excessively heavy have ever lost just 10% of their body weight for just one year. That’s based on self-reports, the national survey, and it’s probably overestimated because people are typically a little optimistic about their accomplishments. Just 10% of their body weight is not even much of the problem for many people who have significant obesity.
We have to recognize that the current approach has failed. It’s a miserable failure. The success rate of obesity treatment is worse than the treatment of almost every cancer. Ironically, we typically blame people for that failure.
“We are not considering the possibility that the advice we have given people is actually the problem. Instead, we are just blaming people for that failure.”
Christiane: Yes, we shame them.
David: “If you are not succeeding it must be your fault. You just have to try harder.” But we are not considering the possibility that the advice we have given people is actually the problem. Instead, we are just blaming people for that failure. The purpose of my book is to look at the new science of weight control without hunger. It turns the calorie balance equation on its head.
We have to address the hormonal drives of weight gain. Let me give you a metaphor. Let’s think back 100 years ago, when people didn’t understand the physiology of fever. Just like many people don’t necessarily understand the biology of body weight control.
100 years ago you went to your doctor with a fever, maybe you had a bad cold or something. Your doctor said, “Well, I’m not sure what’s going on, but really it’s just a problem of heat balance—too much heat in the body and not enough heat out of the body.” From a physics perspective that’s correct. So your doctor said, “Just get into an ice bath and you will remove the heat from your body and you will break the fever,” and of course that would work, right? If you got into an ice bath, you would suck heat out of your body and your temperature would go down. But what’s going to happen?
Your body is going to fight back severely—intense shivering, blood vessel constriction, and you are going to have an overwhelming desire to get out of that ice bath as soon as possible. That is a primitive approach to treating fever. If you address the underlying biology, give aspirin, or treat the source of infection, then you lower the body temperature set point and your body releases that extra heat without any struggle. After the aspirin, you start sweating, you throw off your clothes, your body temperature declines naturally.
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The same thing is true in obesity. If you treat the underlying problem, these fat cells in calorie storage overdrive, your body naturally wants to get rid of those excess calories. Your body weight standpoint declines and you lose weight with your body’s cooperation, not with your body kicking and screaming.
Christiane: Let’s take some calls [from the audience]. We have some good ones…
Caller: I have been a dieter for years. My question is: I am not a big sugar eater, so what are the hidden sugars in foods? Especially after turning 50, I have been gaining 10 to 15 pounds a year and I don’t know what to do anymore. I think maybe I am starving my body. I’m not sure.
David: In terms of sugar, we need to be thinking in a broader context. When you eat processed sugar, added sugar, or for that matter almost any processed carbohydrates—that includes white bread, white rice, potato products, the low-fat cookies, crackers and the like—these are digested into sugar. All carbohydrates turn into sugar, but the processed ones turn into sugar very quickly. Fructose slams into the liver. The glucose raises your insulin levels and that takes a direct hit on your fat cells.
As we cut back on added sugars, ideally, we will be eating less processed food. But if you eat it, read the label. Don’t just eliminate the added sugar and eat more bread. That’s not the trade-off we want. We want to cut back on all of these processed carbs, increase the healthy fats. That’s the easiest and most delicious way to do it. Unprocessed carbohydrates are fine, like whole fruits, beans, and for many people, some minimally processed grains.
Christiane: What is your take on nighttime eating? I know of many, many people who begin their evening meal at 5 and end it at about midnight.
“You don’t want to be creating a battle between biology and behavior. That’s not a battle we are going to win, so you have to be kind to yourself, but disciplined.”
David: That’s a really common and unhealthy pattern, too. People eat tremendous amounts in the evening and at night and then they wake up sick to their stomach and don’t want to eat until later in the day, when at that point the body is back in starvation mode and you overeat again and propagate this vicious cycle. That separates when the food is going into the body from when the calories are actually being used. We want to get that match as accurately as possible. Ultimately having a reasonably sized breakfast, lunch, dinner and depending on how physically active you are, perhaps a snack or two is okay. To make that transition I don’t have people just stop eating at night.
Christiane: You are a very kind man.
David: No deprivation. Listen, there’s too much deprivation already. To change our behavior takes effort. You don’t want to be creating a battle between biology and behavior. That’s not a battle we are going to win, so you have to be kind to yourself, but that lets you be disciplined. We first start by having a little, tiny breakfast. Most people, even if they have binged the night before, they can have just a piece of whole fruit. That’s easy enough. You have a tiny breakfast and then you eat a little less that night, and then the next morning you have a little bigger breakfast, maybe a little tiny lunch and then eat a little less, until you have shifted over a week or two to a more natural distribution of food.
Christiane: That’s beautiful. A person who called said she has been diagnosed with a fatty liver, so she is worried about eating more fat. Lay that one to sleep, would you?
David: This is so important. We have been sold a bill of goods that is completely untrue, as part of this, “you don’t want to have fat on your body don’t put that into your body” concept, which has no scientific basis at all. It’s an emperor without clothing. Farmers for centuries have known if you want to fatten an animal, if you are a French farmer and you’re trying to make pate d’ flora, fatty goose liver, you don’t feed them fat. You feed it processed carbohydrates. You feed them grains.
You don’t even have to feed sugar. You just feed grain and force-feed it so the grains rapidly turn into sugar. The sugar goes right into the liver and further programs the liver for fat storage.
It’s very clear now that a higher fat, lower carbohydrate diet is about the fastest way to drain the liver of its excessive fat.
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Christiane: David, did you ever have any issues with your own weight?
David: When I was younger I was lean and fit, very athletic by nature, and that had really become part of my self-identity. Then, like so many people, beginning in my 20s and 30s, I was adding a pound or two a year. In the mid-90s, just as I was finishing my endocrinology training and beginning to get into research on weight control, I had just about crossed the pivot point from normal weight of body mass index to an overweight one. I was having a bit of an identity crisis, being an obesity researcher myself.
“Even with the perfect diet, we live in a society that is full of temptations, full of stress, and we need community support to stay on track. Ultimately, we have to work together to make the world a less toxic place.”
I remember my waist had gone from 30 when I was 18, to 34 and 35. Fortunately, at that time I came across old studies and thinking that questioned the calorie in-calorie out model and caused me to undergo a radical change from how I was approaching my career. I ultimately shifted out of laboratory research into clinical research with people, which is to me much more gratifying and much more immediately relevant to the problem.
I also changed my own eating pattern. I always had eaten more or less healthy for pretty much what the food guide pyramid recommended, lots of whole grains and fruits and vegetables. An afternoon snack would be an orange scone and tea. That would revive me, but then I would crash again a few hours later and be starving for dinner.
When I greatly reduced these processed carbs, flooded my diet with healthy fats, and made sure to get enough protein, within a few days it was like a metabolic switch was flipped. I felt a miraculous sense of well-being. After eating I would feel great, and hunger would stay at bay for hours rather than experiencing these cravings soon after eating.
Without trying to lose weight, about 20 pounds melted off over four or five months and I went back to a waist size of 31. I’m more like 32 now. Over those last 20 years, statistically my weight would have continued to increase by a pound or two a year. Right now I am pretty much the same weight as I was when I was 18.
There are always going to be challenges. Even with the perfect diet, we live in a society that is full of temptations, full of stress, and we need community support to stay on track. Ultimately, we have to work together to make the world a less toxic place, where the healthful choice is the easy and convenient choice and also ultimately, the inexpensive choice.
Christiane: JAMA came out with those documents that the sugar industry had been influencing the scientific community starting in the 70s in the halls of academia, and you and I both know that the wheels of medicine turn very, very slowly. I have been told that the time it takes for something that’s really helpful and not harmful to get into common practice is about 17 years. What are you seeing in the field when you walk around the hospital with your colleagues?
David: I wrote a recent commentary for JAMA and also an op-ed for CNN, pointing out how just 17 years ago people were recommending sugar. Some of these folks were the leaders in the field of nutrition and in the government recommending sugar as a good way to literally “dilute fat calories.” The idea was there was a sugar-fat seesaw. All carbohydrates were thought to be at worst benign—and now where are we?
Well, no self-respecting nutritionist that is not associated with the [sugar] industry is making that statement now. People are widely beginning to see that just because sugar has fewer calories per gram than fat does not mean that it’s healthy. We have to begin thinking about food based on its metabolic and hormonal effects. That’s a sea change.
Calories are an interesting scientific concept. They’re irrelevant to weight control, just as measures of body heat are irrelevant to how we control temperature. If we get the inputs right, the body controls its temperature, its respiratory rate, and a whole set of other functions perfectly well. The same is true for body weight, although the timeframe for that is a little longer than the timeframe for temperature control.
