How processed food drives diet-related diseases

As a nutritionist, I have been privy to lot of debate in the nutrition world about which foods keep us healthy and which foods actually cause disease.

Different foods offer different nutrient benefits for overall health. And even packaged foods can be enjoyed as part of a healthy diet.

“The food industry works diligently to deliver a consumer marketplace full of healthy, accessible, nutrient-dense food and beverage choices,” said Krystal Register, registered dietition and director of health and well-being at FMI — The Food Industry Association, in a statement to CNN.

But I know the unhealthy eating habits I see are often related to eating too many ultraprocessed foods rich in sugar, salt and unhealthy fats.

That’s why I was eager to talk to pediatric neuroendocrinologist Dr. Robert Lustig about his new book, “Metabolical: The Lure and the Lies of Processed Food, Nutrition, and Modern Medicine.”

Lustig, a professor emeritus at the University of California San Francisco who is dedicated to treating and preventing childhood obesity and diabetes, is also the bestselling author of “Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity, and Disease,” which discusses the dangers of excess sugar, its relation to obesity, and what we can do about it.

This conversation has been condensed and edited for clarity.

CNN: You suggest that the food industry has altered the food we eat, knowing it can kill us. Really?

Dr. Robert Lustig: Really. The food industry knows that when they concentrate sugar, it becomes addictive. The more sugar you add to processed food, the more addictive it becomes. They also know that when they concentrate sugar, it causes liver fat, which leads to insulin resistance, metabolic syndrome and death. They do it anyway.

CNN: Doesn’t the quantity of sugar we eat play a role?

Lustig: Yes, if you could modify the quantity. But you can’t, not with addictive substances. That’s why they are addictive.

It’s the same thing with all hedonic substances like cocaine, nicotine and heroin. When someone says, “I have a horrible sweet tooth,” that is sugar addiction. Do you really think people can moderate their food intake when the food has been engineered to do the exact opposite?

[Editor’s note: There isn’t universal agreement among scientists and nutritionists that sugar or processed foods are addictive. Separately, CNN asked P. Courtney Gaine, a registered dietitian and president and CEO of The Sugar Association to comment on Lustig’s statements. Gaine said that “Inflammatory and unsubstantiated rhetoric about sugar, or any other aspect of the diet, gets us no closer to the goal of healthy consumers.”]

CNN: How do we distinguish between addictive processed food and other kinds, such as canned beans and frozen vegetables?

Lustig: There are different levels of processing. In Brazil’s NOVA food categorization system, Class 1 is food that is unadulterated in any way, shape or form, like an apple. Class 2 is food that is mechanically dispersed, like apple slices. Class 3 is where something has been removed or added, like applesauce, and class 4 is where you have destroyed the matrix of the food, and have added the ingredient to other foods for palatability — like an apple pie. Usually fiber has been removed, and sugar has been added.

Class 4, the ultraprocessed category, is the one that predicts morbidity and mortality, and is 56% of the food and 62% of the sugar consumed in the United States.

CNN: Talk to me about the relationship between sugar and diabetes.

Lustig: First, in order to show that sugar causes diabetes, we have to show that the toxicity of sugar is independent of its inherent calories. And we have to show that the toxicity of sugar is independent of obesity. Second, correlation is not causation.

There are only two levels of data that can tell you whether something is causative. One is randomized controlled trials, and the other one is called econometric analysis.

Do we have either of these two for sugar and diabetes? Yes, we do.

In 2013, we took three data sets that spanned 10 years. This econometric analysis showed that total calories had no relation to the change in diabetes prevalence in all of the countries over the decade. And all the other items — no signal, except for sugar. The effect of sugar on diabetes was very robust. If a country had an extra 150 calories per person per day, diabetes prevalence went up 0.1%. But if that 150 calories happened to be a can of soda, diabetes prevalence went up elevenfold or 1.1%. And in the United States, we’re not consuming one can of soda per day, we’re consuming (on average) the equivalent of two-and-a-half cans.

In another study, a randomized controlled trial, we took sugar out of the diets of 43 children with metabolic syndrome. Since that would reduce their calories by about 400 per day, we replaced the sugar with starch, since we wanted them to stay the same weight. We took the pastries out, and put the bagels in. We gave them foods kids would eat, but food with no added sugar. These kids all kept their weight stable.

Ten days later, we found that every single aspect of their metabolic health improved. We measured their fat deposits — subcutaneous fat and visceral fat and liver fat. And what we found was that their subcutaneous fat didn’t change because they didn’t lose weight. Their visceral fat (belly fat) went down 7% but their liver fat went down 22%.

It’s the liver fat that causes the liver to be dysfunctional, which causes the pancreas to make more insulin, which drives chronic metabolic disease. The improvement in insulin response showed their metabolic disease reversed, just by taking the sugar out of their diets and replacing it with starch. That is causation.

CNN: You say changing what we eat can reduce the risk of many diseases, because a healthy diet will address mitochondrial dysfunction, which is when the structures that produce energy for a cell malfunction, ultimately leading to chronic disease. You say that this problem is foodable, though. Explain?

Lustig: A diet that protects the liver and feeds the gut is “foodable.” This means a low-sugar, high-fiber diet. Real food. This includes anything that came out of the ground and any animal that ate what came out of the ground.

All food is inherently good. It’s what we do to the food that is not. People should see a food label as a warning label. What you really need to know is what has been done to the food, but that is not on the label. But here is how you can know: First, if a food doesn’t have a label, that’s good, because nothing has been done to it. Second, if a food does have a label, look for three things:

1. If sugar is one of the first three ingredients, it’s dessert. Put it back. The problem is there are 262 names for sugar. And that’s on purpose. The industry hides the sugar in plain sight.
2. Look at the fat. If it says soybean oil or palm oil or cottonseed oil or any of these seed oils — these are omega-6s and these have been added. These are pro-inflammatory, and that’s a problem.
3. Look at the fiber. Take the total carbohydrate and divide by dietary fiber, and if the ratio is less than 5 — then it is OK. It means that the manufacturer didn’t take much fiber out in the processing.

CNN: When it comes to weight management, you say type of calories we consume matters. Can you explain?

Lustig: Take almonds — you eat 160 calories, but you only absorb 130 calories. What happens to the other 30? They are for the bacteria in your intestine. We are all eating for 100 trillion, the bacteria of the gut microbiome. It’s not how many calories pass your lips; it’s how many calories get absorbed. Fiber is the nutrient you don’t absorb.

If you don’t feed your bacteria, they feed on you. You get “leaky gut” and inflammation, which leads to insulin resistance, weight gain and disease. A high-fiber diet reverses that.

CNN: What about artificial sweeteners? Can they help us if we have a sweet tooth and want to limit sugar?

Lustig: We don’t know for sure. Artificial sweeteners still trigger insulin. The message for sweet goes from the tongue to the brain, then the brain to the pancreas, which says, “sugar is coming, release the insulin,” but then the sugar doesn’t come because it was a diet sweetener. Does the pancreas hold back on releasing the insulin? No, so you gain weight just the same (as if you consumed excess sugar).

CNN: Do you believe that eating “real food” over processed food will prevent life-threatening diseases?

Lustig: Yes. Genes play different roles in different diseases. Monogenic diseases, like sickle cell disease and cystic fibrosis, involve mutations of one gene. These diseases can’t be modified by diet.

But chronic diseases, like heart disease, Alzheimer’s disease, and nonalcoholic fatty liver disease, are polygenic, which means environment plays a much bigger role.

If you are prone to a chronic disease, the single best thing you can do is to fix your environment in order to fix your mitochondria. That means don’t poison them. What poisons them? Sugar is No. 1. A lack of omega-3’s is No. 2. A surplus of omega-6’s is No. 3. A lack of fiber leading to leaky gut is No. 4.

Fixing your diet doesn’t mean you’re assured of being successful, but dumping the processed food is the single most effective, if not the easiest thing you can do to restore, health, vitality and longevity.