Dr. Robert Lustig is the anti-sugar man. In his popular YouTube lecture, "Sugar: The Bitter Truth,", a subsequent profile in the New York Times Magazine and his best-selling book, Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity and Disease he explains how the sweeteners in our food contribute to metabolic disorders associated with obesity.
But Lustig believes we shouldn't associate these illnesses only with a high body mass index (BMI). In a new study published in PLoS One, Lustig of the University of California, San Francisco, and Dr. Sanjay Basu of Stanford University set out to show that the availability of added sugar in the human diet may have a direct effect on Type 2 diabetes rates, independent of obesity levels, calorie intakes and many other related factors.
"Obesity costs us zero dollars and causes zero deaths," Lustig told HuffPost. "Chronic metabolic disease, which is associated with obesity but may have additional or different causes, costs us $192 billion per year."
Marion Nestle, a professor of nutrition, food studies and public health at New York University, agrees with that sentiment to a degree. "Obesity is a risk factor, not a disease," said Nestle, who was familiar with Lustig's paper but did not contribute to it. "But there is a very clear correlation between diabetes and obesity -- anyone can see it."
Lustig points to research that shows that as many as 40 percent of people who are at a healthy weight, as defined by their BMI score, have some aspect of metabolic dysfunction, such as hypertension, high cholesterol or Type 2 diabetes. On the flip side, 20 percent of obese people do not have any associated metabolic condition. He holds diets with an excess of sugar, or lack thereof, responsible for this discrepancies.
His study tried to isolate the direct effect of sugar in the diet on countries' rates of Type 2 diabetes. It found that every 150-calorie increase from a sugar source -- cane sugar, high fructose corn syrup and other sweeteners-- correlated with a 1.1 percent increase in the Type 2 diabetes rate over a 10-year period, from 2000 to 2010. In other words, the more sugar in the food supply, the more cases of Type 2 diabetes were diagnosed.
While sugar availability has been trending up worldwide, a handful of countries (including Bangladesh, South Korea, Albania and Nigeria) have seen declines, thanks to changes in trade agreements, Basu explained in an email. Those countries provided the researchers with a real-world experiment into whether Type 2 diabetes rates would decline in response to reduced sugar. They found that diabetes rates did, in fact, decline in those instances.
"It's totally plausible," said Dr. David Katz, founding director of Yale University's Prevention Research Center. "A direct link between sugar and diabetes stands to reason, and the food industry uses variations on sugar as additives to enhance the palatability of food -- to make it tastier and irresistible, while downgrading its quality."
"But sugar isn't the only problem," Katz added, saying that starches and other high-glycemic-index foods can be just as harmful to health.
Lustig, Basu and their team analyzed food supply data from the United Nations Food and Agricultural Organization for 175 countries to determine how much sugar was available. They controlled for certain other aspects of the diet, such as fiber, oils, cereals and meats. When they also controlled for the countries' gross domestic product, obesity levels and quality of diabetes surveillance, they found that as sugar availability rose, so too did the prevalence of Type 2 diabetes. One limitation of the study is that the researchers were unable to control for all aspects of diet, including refined flour and starches.
While Lustig sees sugar as a menace unto itself -- causing fatty deposits around the liver that contribute to insulin resistance and fostering dysfunction of the pancreas that stalls insulin production -- many other medical experts, including Katz, believe that a high glycemic diet -- whether from sugars, starches or many other processed and high-calorie sources -- can cause the same damage.
"It shouldn't surprise anyone that eating a lot of sugar is bad for your health," said Nestle. "Obesity is correlated with diabetes and calories have to do with diabetes, but it's difficult to separate calories from sugars. It's also quite possible that people who eat sugar take in more calories and are fatter."
Katz noted that since sugar makes food more palatable, people are apt to eat more of a sugary food, increasing their overall calorie load and contributing to obesity.
"Looking at their data, for every increase in BMI, there is a greater associated rise in diabetes rate than there is for the same increment of added sugar," Katz said. In other words, obesity had a stronger relationship with Type 2 diabetes than sugar consumption did.
"There is really no doubt that obesity is a statistical risk factor for diabetes; our study was not designed to rebut that idea at all," explained Basu to HuffPost. "Rather, it was designed to investigate an additional possibility that the availability of sugars may also have an independent role in diabetes, even aside from contributing to weight or total calories consumed. This could explain some puzzling findings about why diabetes rates among some populations have escalated independent of changes in obesity rates."
The researchers said they hoped their study would help inspire policies that deal with added sugar as a public health threat. The National Health and Medical Research Council of Australia, for instance, released a recommendation this month to limit the amount of added sugar in the daily diet.
"It's really important in this area of research not to cherry-pick individual pieces of research, and that's why I'm emphasizing the 55,000 pieces of research we looked at in the last 10 years," said professor Warwick Anderson of the Australian council. "I just want to emphasize that we've looked at the totality of evidence."
The U.S. Department of Agriculture does not have a specific, numbers-based recommendation for added sugars, but Dr. Robert Post, director of the USDA's Center for Nutrition Policy and Promotion, told HuffPost that if an individual followed the department's MyPlate guidelines, his or her intake of added sugars would be about 5 to 15 percent of total calories.
One thing that nutrition experts do agree on is that sugar from processed foods is a major problem.
"Frankly, this is a product of willful engineering of the food supply," said Katz. "Overall nutritional quality is the problem."