Obesity is not reducible to laziness or a lack of self-control. According to neuroendocrinologist Robert Lustig, it is rooted in biochemical processes, and sugar, primarily fructose, plays the key role in them. Below are his main claims, arguments, and practical recommendations.

Scientific Path and Initial Observations

Lustig works as a pediatric neuroendocrinologist. He studies how the brain regulates hormones and how hormones affect the brain. For about 47 years he has been treating patients, and for the last 19 years he has focused specifically on making healthy food cheaper than the products sold in stores.

The starting point was children with brain tumors. After treatment, some of them developed pituitary disorders and severe obesity. Lustig observed about a hundred such patients at the St. Jude Children's Research Hospital oncology center in Memphis, Tennessee.

Before the tumor, these children had normal weight. After treatment, they gained about 20–30 kg per year and ultimately weighed about 150–200 kg. Neither diets, physical exercise, lifestyle changes, nor drug therapy produced any results.

Based on data from animal experiments, Lustig hypothesized that:

• the vagus nerve connects the brain with the pancreas;
• when the brain is damaged, the vagus nerve becomes hyperactive and forces the pancreas to secrete an excess of insulin;
• severing the vagus nerve stops this process.

About 30 years ago, St. Jude staff conducted a study with octreotide, a drug that suppresses insulin release at the level of the pancreas. Eight children with so-called hypothalamic obesity received it. Their insulin levels decreased, and they began to lose weight. In addition, they became more active: before treatment, the children mostly sat, ate, and slept.

Then a double-blind placebo-controlled study was conducted with a questionnaire on physical activity and lifestyle. The results confirmed the observation: in patients whose insulin levels dropped under the drug's effect, weight decreased and physical activity increased. Later, researchers showed that increased alertness is also associated with lower insulin levels.

Lustig concluded that the root cause of the problem is insulin itself. He began speaking about this publicly around 2004.

Why Insulin Is Elevated in People Without Brain Damage

Most people do not have a brain tumor or vagus nerve disorders. This means that elevated insulin in them has a different cause.

Around 2006, Lustig was invited to speak at a symposium at the National Institutes of Health. The topic concerned an external factor that, in his view, is primarily responsible for weight gain in the United States.

As a pediatrician, he noted two diseases that had previously been seen only in adults: type 2 diabetes and fatty liver disease (steatosis). Adults with steatosis were mostly people with alcohol dependence. Children do not drink alcohol, so Lustig looked for a substance that acts like alcohol.

He compared the metabolic pathways of alcohol and fructose, the sweet component of sugar, and found no differences between them. Mitochondria, the energy stations of cells, normally process glucose. However, they handle alcohol poorly and also struggle with fructose. According to Lustig, fructose and alcohol equally reduce the mitochondria's ability to burn energy and direct it into fat.

Lustig's conclusion: overeating and physical inactivity are not signs of weak character. They are the consequence of a biochemical disorder caused by mitochondrial dysfunction against a background of excess sugar.

Obesity in Newborns

According to Lustig, the obesity epidemic has also affected infants. He presented data from four studies: the United States, Russia, South Africa, and Israel. Over the past 25 years, the average birth weight in these countries has increased by 200 g. Densitometric scanning showed that the entire increase was attributable to adipose tissue.

Lustig believes that the explanation based on laziness and gluttony is untenable, since newborns cannot be responsible for their diet or activity. In his view, the concept of personal responsibility is promoted by the food industry in order to shift responsibility for the epidemic onto consumers.

According to him, the mechanism works as follows: when mitochondrial function is impaired, the body does not receive enough ATP. A person experiences a loss of energy, tries to compensate for it with food, and becomes less active. Thus, overeating and physical inactivity are the consequences of biochemical processes, not their cause.

Sugar as a Toxin

Lustig defines a toxin as any substance that damages cells. According to him, fructose damages cells, and all the toxins he lists act on mitochondria.

He reminded us that the Swiss physician and alchemist Paracelsus formulated the principle: "the dose makes the poison." Lustig gives the following examples:

According to him, all these substances disrupt mitochondrial function. Only the doses and the degree of chronic exposure differ.

Lustig also described a case of Reye's syndrome that he observed early in his career. Reye's syndrome, a severe liver failure with fatty infiltration, developed mainly in infants and young children, and most patients died. In the early 1980s, epidemiological studies showed that all the patients had been taking aspirin. Since then, it has not been prescribed to children. According to Lustig, aspirin also suppresses mitochondrial function.

He compares fructose with alcohol:

• A small dose of alcohol, for example one glass of whiskey, is harmless; two glasses may cause harm.
• Three glasses a day, according to laboratory studies, are probably harmful, including because of the risk of traffic accidents.
• Four glasses a day make detention by police highly likely.
• Five glasses a day, according to Lustig, indicate alcoholism and lead to death from liver disease or earlier.

Conclusion: alcohol is tolerated in small doses but remains a toxin that damages the liver with chronic use. By Lustig's classification, aspirin is a dose-dependent acute liver toxin, while fructose, like alcohol, is a dose-dependent chronic liver toxin.

Criteria for Regulation

Lustig compares fructose with other substances that are or are not regulated by the state:

• Water. Toxic when consumed in excess, but not regulated.
• Oxygen. Breathing 100% oxygen can damage the lungs. Not regulated.
• Vitamin D. Not regulated, as it has no potential for abuse.
• Caffeine. According to Lustig, it is 100% addictive but not toxic. Not regulated. He considers five to six cups a day acceptable. Mixing caffeine with alcohol, as in the Four Loko drink, can, in his words, cause arrhythmia and death.

In Lustig's view, fructose is both toxic and addictive. Public health uses four criteria for regulating substances:

1. Ubiquity. The substance is present everywhere.
2. Toxicity. Lustig considers fructose a chronic mitochondrial toxin.
3. Abuse. The substance is addictive.
4. External costs. Consumption affects other people. Lustig compares this to smoking and alcohol, which harm others.

By his calculations, the external costs of sugar amount to $10 trillion per year. He listed the components:

• Global revenue of the food industry from sales of sugar-containing products: $9 trillion per year.
• Healthcare costs due to metabolic syndrome caused by excess sugar: $11 trillion.
• Environmental costs of growing sugarcane and sugar beets: $7 trillion.
• Productivity losses due to metabolic diseases: about $1 trillion.

According to him, healthcare systems in many countries are overburdened: patients wait for catheterization and dialysis, and it is difficult to make an appointment with a doctor.

Safe Sugar Doses

Lustig specifies safe daily limits of added sugar:

Part of the sugar is processed by the intestines, and the liver can also absorb it. Lustig believes that sugar should not be eliminated entirely, but should be consumed rarely and in limited amounts.

A 350 ml can of Coca-Cola contains 39 g of sugar. According to him, one can a day already exceeds the limit, not counting breakfast, lunch, dinner, and snacks.

Juices, Fruit and Fiber

Lustig distinguishes between fruit and juice. Fruit is healthy, juice is harmful. Juice lacks the fiber found in the pulp of fruit. According to him, fiber is the beneficial part of the fruit, while juice contains mainly sugar.

He explains that an 8-ounce (about 240 ml) glass of juice requires four oranges. It is difficult to eat four oranges at once, and people usually do not consume fruit in such quantities. In whole fruit, fiber limits the intake of sugar.

According to Lustig, many nutritionists claim that fiber is needed only for forming stool and is not absorbed by the body but is broken down by intestinal bacteria. He responds that fiber is food for the microbiome, and a healthy microbiome is essential for preventing inflammation in the intestines and throughout the body.

The Intestinal Defense Mechanism

Lustig describes a mechanism that he calls the intestinal "second barrier":

• Cellulose (fibers, for example, in celery) works like a colander or a fishing net.
• Soluble fiber, such as pectin and inulin, which give jelly its shape, fills the openings of this structure.
• Together they form a barrier through which fructose, sucrose, and starch cannot pass.

According to him, sugars and starch remain in the digestive tract, are not absorbed, and reach the microbiome. Fiber serves as food for bacteria, and when there is a lack of it, according to Lustig, the bacteria begin to break down the mucin layer of the mucosa. This leads to intestinal irritation, inflammatory bowel diseases, and systemic inflammation. Inflammation, in turn, leads to insulin resistance.

Lustig adds that fructose destroys the Th17 cells of the intestinal immune system. Thus, according to him, it acts as a toxin for both the mitochondria and the immune cells of the intestine.

He cites the ratio: the body contains about 10 trillion cells and about 100 trillion bacteria in the intestines, meaning there are 10 times more microbes than cells.

Sugar and the Immune System

Lustig argues that sugar does not suppress the immune system but activates it indiscriminately. When cells experience an ATP deficit, the immune system perceives this as an infection and switches on unnecessarily. A normal immune system, in his words, should respond only to a real threat.

He links this kind of activation to the risk of autoimmune diseases, in particular systemic lupus erythematosus, rheumatoid arthritis, and Crohn's disease.

According to Lustig, chronic inflammation is associated with excess sugar, but not only with it. He also names:

• ultra-processed foods;
• air pollution;
• ionizing radiation;
• microplastics;
• bisphenol A (BPA);
• PFAS;
• phthalates;
• glyphosate;
• infections, such as the Zika virus, which, in his words, disrupts mitochondrial function.

Lustig assesses the contribution of these factors as follows: 80% of the problem is related to nutrition, and 20% to toxins and infections. In his words, nutrition can be changed as early as tomorrow, given political will.

He also points out that environmental cleanup, such as a large-scale program against microplastics, would, in his estimate, require spending equal to ten times global GDP over 10 years. He considers such a scenario unlikely. Microplastics and PFAS, in his words, have already become part of everyday life. For example, every American has PFAS in their blood.

Lustig gives the example of DDT. In her book Silent Spring (1962), Rachel Carson described how DDT kills not only insects but also people. It was banned in 1972. However, DDE, a metabolite of DDT, is still detected in the urine of Californians. In his words, DDE levels allow one to predict obesity and cognitive function in offspring. He concludes that toxins cannot be completely eliminated, but diet is under human control.

Industry and Corporate Influence

According to Lustig, 62% of products in American grocery stores contain added sugar. For children's products, this figure is 67%. Later he also cites a figure of 74% for all products in American stores. By his account, Europe shows a similar picture, with somewhat lower figures according to data from the United Kingdom.

Ultra-processed foods, by definition, contain a lot of sugar and little fiber. Lustig considers them the root of the problem: he calls sugar the projectile, and ultra-processed foods the gun from which the projectile is fired.

Lustig refers to a study by his colleague Tara Fazzino from the University of Kansas. According to this study, from the mid-1980s to the early 2000s, several American food companies were acquired by tobacco corporations:

• Altria (then Philip Morris) bought General Foods;
• R.J. Reynolds, a well-known tobacco brand, acquired Nabisco.

According to Lustig, after these deals, the sugar content of these companies' products increased significantly. He argues that this was a deliberate decision, since producers knew about sugar addiction, just as tobacco companies increased the nicotine content of their products.

In March, the New England Journal of Medicine published an article by Lustig and co-authors, "Corporations as Vectors of Chronic Disease." By his account, corporations function as disease carriers, much like mosquitoes that carry malaria.

The University of California, San Francisco, Stanford, and the University of Sydney have established the Center for the Study of Corporate Harm. The University of California's Industry Documents Library holds 29 million documents. They are systematized and digitized, and access to them is open (website: idl.ucsf.edu).

According to Lustig, the library contains documents from six industries: opioids, pharmaceuticals, tobacco giants, the oil industry, alcohol, and ultra-processed foods. A seventh library, he says, is being created on the arms industry.

Lustig believes that manufacturers understand the consequences of their actions and seek to extract profit at the expense of consumers. In his view, the food industry will not change until it is forced to.

Ultra-processed foods and added sugar

Lustig gives examples of products with added sugar: ketchup, yogurt, cheese, salad dressings, and chicken. According to him, poultry is soaked in a sugar solution to make it look juicier. Tobacco leaves, he says, are also deliberately treated with a sweet solution, since sugar intensifies nicotine addiction.

He explains that sugar is added to boost sales: the more sugar, the more people buy. According to him, in the US some products are also colored; for example, salmon gets an orange dye.

Lustig notes that the "added sugar" label appears on packaging in the US, but he is not sure about the situation in Russia. The presence of such a label on a product, in his opinion, means the product has been processed, so these labels should be treated as a warning. For example, broccoli, radishes, and raspberries have no labels.

Alternatives: Harm Reduction

Lustig believes that ultra-processed foods will remain on the market. By his estimate, by 2050 it will be necessary to feed 10 billion people, and there will not be enough land and ocean to do so. Therefore, in his view, ultra-processed foods, which have longer shelf lives, should be made more healthful rather than abandoned entirely.

He draws an analogy with needle exchange programs for drug users. In 1979, the first patient with AIDS appeared; in 1984, the AIDS epidemic gained momentum. In 1986, the New York City Department of Health began distributing needles to drug users free of charge in order to reduce the spread of HIV. According to Lustig, the program worked, and the spread of HIV declined significantly. This approach is called harm reduction: not approving of the behavior, but mitigating its consequences.

The Baololu Project

Lustig is a co-founder and chief medical officer of Baololu. Its product, a patented fiber formula, is added to food and restores the fiber that the manufacturer removed. The formula contains soluble and insoluble fiber, which binds glucose, fructose, sucrose, and simple starches.

According to him, when processed foods with this additive are consumed, metabolic health improves. Lustig calls this replacement therapy: people receive the fiber they need together with their regular food, without noticing it.

The Project with Kuwaiti Danish Dairy Company

Lustig described a project with Kuwaiti Danish Dairy Company (KDD) of Kuwait, which he called the Nestlé equivalent in the Middle East. The company receives raw materials, including powdered milk and sugar, by sea vessels through the Persian Gulf.

KDD approached Lustig six years ago. The company stated that it recognizes the problem and wants to be part of the solution. The company is privately held, its shares are not traded on an exchange, and its owners are the founder and his sister. They are prepared to invest in long-term projects.

Lustig led a scientific advisory group of five people for three years. The group worked two hours twice a week. It:

1. studied every ingredient, product, and production process;
2. sent raw materials and finished products for biochemical analysis;
3. identified the changes needed for the metabolic safety of the products.

As a result, a system of three rules was formulated, which Lustig called the metabolic matrix: "feed the gut, protect the liver, support the brain." By his definition, a product that meets all three conditions is considered healthy regardless of its degree of processing. A product that meets none of the conditions is considered harmful. A product that meets some of the conditions occupies an intermediate position.

KDD launched the "Good for Me" line by reformulating 10% of its 180-item range, that is, 18 products. According to Lustig, sales did not decline and the taste did not change. Additional investment was required to restructure the supply chain and make changes at the factory. By his account, the manufacturer's profit remained the same.

The experience was presented at the World Economic Forum and discussed at the McKinsey Health Institute. Lustig notes that other companies are in no hurry to adopt such a system, since they fear rising costs without a clear benefit.

The Perfect App

Lustig and his colleagues developed the Perfect app. It displays products in a store and their prices, and filters products by the user's biochemical profile.

Lustig gives an example. A user who is 24 years old has metabolic syndrome, gout, and kidney stones. He needs little sugar, a lot of fiber, fewer purines due to gout, and a minimum of oxalates due to kidney stones. The app works in four steps:

1. It matches the request against the user's biochemical profile, which is stored online.
2. It accesses a database of 2 million recipes and finds all variations of a dish, for example chicken cacciatore (about 20 recipes), analyzing each one for sugar, fiber, purines, and oxalates. It selects the variant with the lowest values.
3. It checks the labels of all products in the store and selects ingredients with the least sugar, the most fiber, and the least purines and oxalates. It adds them to the cart in a delivery service, for example Instacart or Amazon Fresh, or in a comparable service in Russia. Products are delivered by 3:00 p.m. together with the recipe.
4. It sends the receipt to the insurance company for reimbursement.

According to Lustig, such a diet reduces the manifestations of metabolic syndrome, gout, and stones, so the insurer saves money on treatment. The food costs about 1% of the cost of medications.

The host noted that the system requires regular blood tests. Lustig replied that monthly testing is excessive, but annual testing is mandatory.

Diagnostics: Fasting Insulin

Lustig considers measuring fasting insulin the most important test. Insulin rises with mitochondrial dysfunction: when mitochondria cannot process glucose, the excess is directed into fat. Therefore, elevated fasting insulin, in his words, indicates impaired mitochondrial function.

The American Diabetes Association does not recommend this test. Lustig addresses its two arguments:

1. Different laboratories use different methods, and the results vary. Lustig acknowledges this but believes that when one method is used, the results are comparable, and a high level always indicates a problem.
2. Fasting insulin levels do not correlate with obesity. Lustig responds that hip and buttock obesity (subcutaneous) is not dangerous, whereas visceral obesity (fat in the abdominal area) is. Fasting insulin reflects visceral and hepatic fat, while subcutaneous fat in the buttocks, in his words, belongs to "good" fat.

Lustig considers glycated hemoglobin (HbA1c) a marker of diabetes, but a late one. Its level changes with a significant delay, so it does not provide an early signal. Lustig supports the HbA1c test but does not consider it sufficient.

Reversibility

According to Lustig, metabolic diseases can recede when diet is changed, and this is confirmed by data. He describes three stages of liver steatosis:

1. fat;
2. fat and inflammation;
3. fat and scarring.

Recovery is possible at the first and second stages. At the third stage, the process is irreversible, and only a transplant can help. In his words, more and more people are reaching this point.

The host said that after the interview he would check his insulin level, and Lustig urged viewers to do the same.

Legal Cases and Public Perception of the Problem

Lustig served as an expert witness in court cases against Kellogg's and Mondelēz over BelVita cookies. He argued that a product with a high amount of added sugar cannot be called healthy, even if it contains vitamins. The companies' lawyers stated that current legislation does not prohibit such labeling.

In his words, courts view sugar only as calories. To change this, public awareness must first be raised.

Lustig cites survey data from the International Food Information Council (IFIC), which, he says, is a PR organization for the food industry:

• 2011. Asked "Which product is most likely to lead to weight gain?", 33% of respondents named sugar, 33% named saturated fats, and the rest said they didn't know or that a calorie is a calorie.
• 2018. The same question. 33% named sugar, while the share of answers about saturated fats decreased by the same amount.

In his view, this shows a rise in awareness of added sugar.

Pleasure and Happiness

In 2009, Lustig gave a lecture titled "Sugar: The Bitter Truth," which, according to the host, was viewed about 25 million times. Lustig noted that critics fall into four groups:

1. Dinosaurs. Scientists who adhere to the concept of calorie balance and receive grants for calorie research.
2. Deniers. For example, athletes who consider sugar harmless because of intense training.
3. Dilettantes. Food industry employees who must maintain share prices and production volumes.
4. Addicts. People who are not ready to give up sweets.

Example of a Denier: Sami Inkinen

Lustig told the story of his colleague Sami Inkinen. He graduated from the Stanford Graduate School of Business and founded the real estate service Trulia, which Zillow later bought for $3 billion. He then founded Virta Health, which uses a ketogenic diet to treat diabetes.

At 38, Inkinen, a triathlete who trained 5 hours a day, began to lose performance and developed glucose intolerance. He consulted Steve Phinney of the University of California, Davis, one of the first specialists in low-carbohydrate ketogenic nutrition. It turned out that the cause was sports drinks. After he stopped drinking them, liver fat decreased, glucose tolerance improved, competition results rose, fasting insulin levels dropped, and his indicators returned to normal.

Pleasure and Happiness: Seven Differences

Lustig wrote the book The Hacking of the American Mind (2017), in which he distinguishes between pleasure and happiness. According to him, these concepts are confused, which fosters addiction. He lists seven differences:

Lustig explains the difference between the neurotransmitters:

• Dopamine signals: "This is good, I want more." It is an excitatory neurotransmitter. Chronic stimulation of a neuron leads to its death. Cells protect themselves by reducing the number of receptors. This creates tolerance: more and more of a substance is needed to produce the same effect, and dependence develops.
• Serotonin signals: "This is good, no more is needed." It is an inhibitory neurotransmitter, so serotonin receptors do not lose sensitivity. According to Lustig, there is no overdose of happiness. However, dopamine suppresses the release of serotonin, so the more a person strives for pleasure, the less happy they become.

Lustig believes that modern society is structured so that companies profit from this weakness. He considers necessary measures to include restricting the activities of such companies, for example social networks and casinos, and recognizing happiness as a value.

Four Sources of Serotonin

Lustig names four sources of serotonin, which he formulates as "4C":

1. Connection. Real relationships with people, rather than social media.
2. Contribution. Participation in the common good, not just personal income.
3. Coping. Managing stress through mindfulness, physical activity, and sleep.
4. Cooking. Serotonin is synthesized from tryptophan, which comes from food. Tryptophan is found in natural foods but not in ultra-processed ones.

Recovery After Overloading the Dopamine System

Lustig notes that the death of dopamine neurons is irreversible. People who have completed drug rehabilitation have a reduced capacity for pleasure, which is why they often return to drug use. He calls this mechanism one of the causes of relapse. Among the well-known examples he cites are Amy Winehouse, John Belushi, and Philip Seymour Hoffman.

Lustig believes the same mechanism operates in gambling addiction and in sugar addiction.

Physical Activity and Diet

Lustig considers physical activity beneficial but secondary in effectiveness to diet. According to him, exercise does not reduce weight directly; instead, it increases muscle mass, which is heavier than fat. Exercise improves health and reduces visceral and liver fat, but these changes are not always reflected on the scale.

Weight is reduced through diet, which lowers insulin levels, while exercise increases insulin sensitivity and reduces insulin resistance. The combination of diet and exercise gives the best results.

Lustig presents data on the efficiency coefficient for metabolic health:

He lists eight subcellular pathologies that, in his view, underlie aging and the development of disease:

1. Glycation
2. Oxidative stress
3. Mitochondrial dysfunction
4. Insulin resistance
5. Membrane stability
6. Inflammation
7. Methylation
8. Autophagy

According to him, nutrition corrects all eight processes, while physical activity corrects four.

Eating Schedule

Lustig recommends eating two meals a day. Three meals, in his view, lead to fat accumulation, while two meals allow the body to use stored energy, including fat and glycogen, and maintain cells' sensitivity to insulin. He also noted that intermittent fasting and the ketogenic diet are based on this principle.

Breakfast, he said, was introduced into the diet by an advertising campaign that made it "the most important meal of the day." Lustig considers this claim incorrect.

He recommends finishing dinner no later than three hours before bedtime. A late dinner, he said, causes energy to be stored as fat, because at night mitochondria do not convert it into ATP and carbon dioxide.

The host asked what to do if someone skips breakfast and feels weak. Lustig replied that these sensations are related to caffeine dependence.

Caffeine, according to Lustig, is less harmful than sugar. It has its drawbacks, but, he said, decades of searching for diseases caused by caffeine have yielded no results.

Early Markers and Concluding Recommendations

5–10 years before blood glucose reaches the diagnostic threshold for type 2 diabetes, the body shows the following signs:

• elevated fasting insulin;
• elevated uric acid;
• elevated ALT;
• elevated triglycerides and reduced HDL (high-density lipoprotein) on the biochemical profile.

Lustig also mentioned GDF15, which, in his observation, is a signal of mitochondrial stress. For now, it is not included in standard tests.

Lustig called "wellness" a buzzword with no practical value. In his words, life extension is impossible without improving health. Improving metabolic health and increasing insulin sensitivity, in his assessment, can add about 10 years to life. Reducing exposure to toxins from food and the environment has a similar effect. He considers this more effective than any longevity supplement.

Concluding the interview, Lustig said that the problem cannot be solved without understanding its essence. For the past 50 years, people have been told that the problem does not exist. He believes he is setting the task of understanding its essence, and that is exactly what he is doing.