Dr. Robert Lustig’s 2009 video “Sugar: The Bitter Truth,” has now garnered nearly 6.5 million views on YouTube. The featured video is a follow-up on that original lecture.

In it, he discusses the metabolic influence of sugar and processed foods on obesity and related diseases. He also reviews the importance of diet versus exercise when weight loss is your goal.

Delving into the science behind different types of sugar, Lustig explains the metabolic differences between glucose and fructose, which is at the very heart of the obesity and diabetes problems.

What Do Rising Obesity and Diabetes Rates Suggest?

According to Lustig, 6 million American children were overweight or obese in 2001. Today that number exceeds 23 million.1 This is despite all the anti-obesity campaigns and measures launched since then.

Clearly, nutritional and weight loss recommendations provided to the public over the past 15 years are deeply and fundamentally flawed.

Worldwide, obese people now outnumber the starving by 30 percent. Fifteen years ago, this statistic was the reverse. Today, 5 percent of the global population is also diabetic. According to Lustig, these kinds of statistics suggest that obesity and diabetes are not due to behavior, but rather exposure.

If the trends continue, it’s been estimated that by 2030, 42 percent of Americans will be obese, and 100 million Americans — nearly one-third of the current population — will have diabetes by 2050. Meanwhile, Medicare is expected to be broke by 2026.

The fact of the matter is we’ve been following the same reasoning for the past 30 years, and the problem of obesity and diabetes keeps getting worse by the year. It is time to reframe how we view the problem, and how we resolve it.

Visceral Versus Subcutaneous Obesity

While 80 percent of the obese population is sick, it’s important to realize that metabolic dysfunction affects normal weight people as well. In fact, about 40 percent of normal weight individuals have the same health problems as those who are obese.

Lustig shows a cross-section image of the internal abdominal cavity of two individuals. They both weigh the same, yet one is healthy and the other is not. The one struggling with health issues has far more visceral fat — the fat that accumulates around the internal organs.

The number on your scale does not tell you how your fat is distributed. It also cannot tell you how much of your weight is due to fat (subcutaneous fat, which is not necessarily bad for your health and visceral fat, which is quite hazardous), and how much is bone or muscle.

Your waist circumference can give you a decent clue, but even this measurement isn’t foolproof, as there are many thin people who fall into the “thin on the outside and fat on the inside” category, a condition referred to as TOFI.

Those with TOFI have the same health problems as obese people, including high blood pressure, diabetes and heart disease.

In short, obesity in and of itself is not the root cause of failing health worldwide. It’s merely another symptom. The real problem is metabolic syndrome, which accounts for 75 percent of all healthcare dollars spent in the U.S. Metabolic syndrome is a cluster of symptoms that include:

  • Diabetes
  • Hypertension
  • Lipid abnormalities
  • Cardiovascular disease
  • Non-alcoholic fatty liver disease (NAFLD)
  • Polycystic ovarian disease
  • Cancer
  • Dementia

Obesity and the Law of Thermodynamics

The law of thermodynamics says that “the total energy inside a closed system remains constant.” Obesity is said to be a result of this law. However, there are two different interpretations of this law.

1. The calories-in, calories-out interpretation. According to this interpretation, you have to use up the calories you ingest, or else the excess calories will turn into body fat and result in weight gain.

If this interpretation was correct, then the solution to weight gain would be a matter of energy balance, which is what the processed food and soda industries would like you to believe.

Since excess food consumption and lack of exercise are both behaviors, based on this interpretation, obesity is caused by personal shortcomings or choice.

The dogma associated with this interpretation is that “a calorie is a calorie,” and it doesn’t matter where the calories come from because they all produce the same results.

2. The energy deposition interpretation. If you accept that calories are NOT created equal and that obesity is the result of aberrant energy deposition, you can interpret the law of thermodynamics in a whole new way.

Essentially, in order to store fat, you have to increase your insulin level, and in order to raise your insulin you have to eat foods that cause it to spike.

As your insulin level becomes chronically elevated, insulin resistance sets in, which facilitates fat deposition. What foods raise insulin? The scientific evidence tells us that the most effective food source to raise insulin is fructose.

But there’s more. As previously explained by Zoe Harcombe, Ph.D, thermodynamics is about the movement of energy. The second law of thermodynamics says that “energy will be lost and energy will be used up in creating available energy,” and the thermic effects of nutrients vary.

For example, the thermic effect of protein, i.e. the energy used up in making protein available to your body, is somewhere around 25 to 30 percent whereas the thermic effect of carbohydrates is around 6 to 8 percent. In addition to that, your body self-regulates based on available energy.

If this interpretation is correct, and Lustig insists it is, the solution to weight gain has nothing to do with “energy balance.” Instead, the answer is to eat real food, which are low in sugar (and devoid of HFCS) and high in fiber and healthy fats.

Moreover, it removes the stigma that obese people are simply gluttonous and lazy, as behavior follows biochemical reactions and not the other way around. Ultimately, this interpretation reveals that obesity is a problem caused by a toxic (and addictive) food environment, not behavior.

Obesity Is a Biochemical Problem

To recap, Lustig persuasively argues that the primary reason causing all of these visceral fat-related health problems is excessive fructose in our diet. Granted, ALL sugars contribute to weight gain to a certain degree, but highly refined and processed fructose, such as high-fructose corn syrup (HFCS), wreaks the most biochemical havoc, by negatively affecting your leptin and insulin sensitivity, which results in metabolic syndrome.

Leptin deficiency, a hereditary medical condition that affects about 14 people in the entire world, causes extreme obesity as the lack of this satiety hormone makes the brain think it’s starving all the time. What most people suffer with today is leptin resistance — a condition in which your body has lost its ability to register the signals from leptin. Still, the effect is much the same.

Leptin resistance, just like leptin deficiency, also causes you to become lethargic, as the brain doesn’t want to expend any energy when it believes it doesn’t have the energy to waste. So, as Lustig explains, obesity is a biochemical problem. It’s not about gluttony and sloth, which are largely voluntary behaviors.

According to his research, it’s quite clear that biochemistry drives behavior, so gluttony and sloth are the downstream results of biochemical dysfunction. They’re not the cause of the biochemical dysfunction.

Other Dietary Considerations

I have not had a chance to discuss this with Lustig and I’m not sure if his position has changed since he recorded this video, but I believe there are two other considerations that may be as significant, or even more of a contributing factor than sugar. Believe me, I’m a strong advocate of avoiding sugar, but that isn’t the entire story.

One also needs to limit protein, as excessive protein may have more of a deleterious health effect than excessive sugar. Most people would benefit from restricting the protein intake to 1 gram (gm) per kilogram (kg) of lean body mass.

So if you reduce net carbs and protein, you are only left with dietary fat, which may be one of the biggest culprits. Most of the fat people eat is unhealthy and consists of processed omega-6 vegetable oil (most of that fat is from soybean oil). In fact, the amount of soybean oil consumed in 2000 was more than 1,000 times higher than it was 100 years ago in 1900.

Insulin Blocking Leptin Is Another Factor

Leptin resistance correlates with higher amounts of body fat. So what blocks leptin from working properly? According to Lustig, once you solve that question, you solve the obesity problem. The answer to this question is insulin.

Insulin resistance produces weight gain, and there’s a biological purpose for this. During puberty and pregnancy, you need to gain excess fat for hormone production and the growth of another human being. So from a biological perspective, there are two life periods during which leptin should be blocked to allow for fat accumulation.

The problem is that for some reason, leptin is now being blocked by elevated insulin levels in a vast number of people all the time. So what causes chronically elevated insulin levels and insulin resistance? The answer is sugar, and more specifically fructose, which places a far greater metabolic burden on your body.

How Fructose Metabolism Gives Rise to Metabolic Syndrome and Obesity

A summary of fructose metabolism is as follows:

– Every cell in your body utilizes glucose. Therefore, much of it is “burned up” immediately after you consume it. When you consume glucose, your liver only has to break down 20 percent of it.

By contrast, cells don’t use fructose for energy, so 100 percent of the fructose you eat is metabolized in your liver. Your liver is the only organ equipped with a fructose transporter, called GLUT5. Rather than being used as a quick energy source, fructose is turned into free fatty acids (FFAs), very-low-density lipoprotein (VLDL, the damaging form of cholesterol), and triglycerides, which are then stored as body fat.

When you eat 120 calories of glucose, less than one calorie is stored as fat; 120 calories of fructose results in 40 calories being stored as fat.

Fructose metabolism is very similar to ethanol metabolism, which has a multitude of toxic effects. The fatty acids created during fructose metabolism accumulate as fat droplets in your liver and skeletal muscle tissues, causing insulin resistance and NAFLD.

As your body becomes increasingly resistant to insulin, your pancreas keeps releasing ever higher amounts of insulin in an effort to curb your rising blood sugar levels. Eventually, your pancreas loses the battle; your blood sugar levels keep rising, and you end up with metabolic syndrome and full-blown diabetes.

– Fructose is the most lipophilic carbohydrate. In other words, fructose converts to activated glycerol (g-3-p), which is directly used to turn FFAs into triglycerides. The more g-3-p you have, the more fat you store. Glucose does not do this.

The metabolism of fructose by your liver creates a long list of waste products and toxins, including a large amount of uric acid, which drives up blood pressure and causes gout.

– Glucose suppresses the hunger hormone ghrelin and stimulates leptin, which suppresses your appetite. Fructose, on the other hand, does not appropriately stimulate insulin, which in turn fails to suppress ghrelin (the “hunger hormone”) and blocks leptin signaling (the “satiety hormone”). The end result is overeating and insulin resistance. In short, fructose tricks your body into gaining weight by turning off your body’s natural appetite-control system.

The Dose Determines the Poison

While fructose is not a toxic substance in and of itself, when it’s consumed in excessive doses, your liver simply cannot metabolize it. And when the overexposure is chronic, metabolic syndrome develops, and this is true even if you’re not obese.

In short, fructose overconsumption damages your pancreas, liver and brain much like alcohol does, yet, despite its similarities, alcohol is regulated and fructose is not. As Lustig says, “You’d never consider giving your kid a beer, but you wouldn’t think twice about giving him a Coke, yet they do the same thing. That’s the problem.”

Another problem relates to the Maillard reaction, i.e., the browning reaction that occurs when glucose chemically interacts with the amino acid group of proteins.

This is what you see when you look at a piece of deep-fried chicken or a piece of toast, for example. Now, the Maillard or browning reaction also takes place inside your body. It’s a normal part of the aging process. The question is, how fast will this happen inside your body? The answer: the higher your fructose intake, the faster this chemical reaction takes place and the faster you age.

Diabetes Rates Correlate to Sugar Availability

By conducting an economic analysis of diet and diabetes prevalence, Lustig’s team was able to determine that changes in sugar availability were the only factor that correlated with changes in diabetes prevalence. For every 150 calorie increase, there was a 0.1 percent increase in diabetes. However, if those 150 calories came from soda, diabetes prevalence increased 11-fold, to 1.1 percent.

Extrapolating data further, Lustig claims that 25 percent of diabetes worldwide is attributable to sugar alone — not obesity or total calorie consumption, but sugar consumption specifically. Moreover, his research reveals how long it takes for increases in sugar consumption to translate into increases in diabetes. No matter which country you look at, three years after a spike in sugar consumption, diabetes rates rise.

“We have causal medical inference that sugar causes obesity,” Lustig says, which means that while more research is always needed, we already have enough evidence to act.

Sugar Is a Highly Addictive Substance

Adding insult to injury, sugar is also addictive. In fact, it’s been shown to be more addictive than cocaine. Sugar hijacks the reward center in your brain, causing brain changes identical to those in drug addicts and alcoholics. A critical player in all forms of addiction, including food addiction, is the neurotransmitter dopamine.

Groundbreaking research into addiction has revealed that you will not feel pleasure or reward unless dopamine binds with it s receptor, called the D2 receptor, which is located all throughout the reward center in your brain. When dopamine links to this receptor, immediate changes take place in brain cells and then you experience a “hit” of pleasure and reward.

However, when you indulge in too much of any hyper-stimulator, be it cocaine, alcohol, sugar or caffeine, your brain’s reward center notes that you’re overstimulated, which the brain perceives as adverse to survival, and so it compensates by decreasing your sense of pleasure and reward. It does this by downregulating your D2 receptors, basically eliminating some of them.

But this survival strategy creates another problem, because now you don’t feel anywhere near the pleasure and reward you once had when you began your addiction, no matter whether it’s food or drugs. As a result, you develop tolerance which means that you want more and more of your fix, but never achieve the same “high” you once had. And so, cravings grow stronger. Addiction to any one substance also increases your risk of cross-addiction to other addictive substances.

Eating REAL Food Is the Answer

The concerted effort by the processed food industry to make their products as addictive as possible has the unfortunate side effect of stimulating your metabolism to burn carbs (sugar) as its primary fuel. As long as you are burning carbs as your primary fuel, you will strongly crave these types of foods.

The solution is to decrease the amount of processed foods and net carbs (total carbs minus fiber — think sugars) you eat, and replace them with real foods, i.e. high-quality whole foods, especially low net-carb vegetables.

As noted by Lustig, every single diet that works is a diet based on real food. Also remember that net carbs (i.e. non-fiber carbohydrates) need to be replaced with healthy fats to successfully achieve this metabolic switchover. Overall, a real food diet is high in fiber and healthy fats, and low in net carbs.

If you suffer from junk food cravings, especially cravings for sugar, know that intermittent fasting is one of the most effective ways to end them. Sugar cravings will dramatically diminish, if not vanish altogether, once your body starts burning fat instead of sugar as its primary fuel.

To protect your health, I recommend spending 90 percent of your food budget on real food, and only 10 percent or less on processed foods. Unfortunately, most Americans do the opposite, which is why so many struggle with junk food cravings, weight gain and poor health.

Remember, virtually ALL processed foods are loaded with HFCS. According to Lustig, of the 600,000 items in the U.S. food supply, 80 percent of them contain HFCS and other added sugars. And the reason for this is because the food industry knows that when they add sugar, you eat and buy more of it, for all the reasons discussed above.

If anyone tries to tell you “sugar is sugar,” or “a calorie is a calorie,” they are way behind the times. As you can see, there are major differences in how your body processes fructose and glucose. The bottom line is: fructose leads to increased visceral fat, insulin resistance and metabolic syndrome — not to mention the long list of chronic diseases that result from it.

To learn more, please see the Institute for Responsible Nutrition’s (IRN) website, responsiblefoods.org. IRN is an organization that Lustig helped set up for the purpose of “providing medical, nutritional and legal analysis and consultation to promote personal and public health against Big Food.”