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August 2011

Is Sugar to Blame for America’s Obesity Epidemic?


The dietary police are on the beat again, and this time they’re telling us that the Twizzler we’ve got in our hand may as well be a cigarette. 

In a recent story in The New York Times Magazine entitled “Is Sugar Toxic?” journalist Gary Taubes reignited a controversy over the baleful effects of America’s favorite sweetener.

The article’s main thesis is that sugar is the driving mechanism behind the current American obesity epidemic and the concurrent rise in heart disease, and that it may even be responsible for some cancers.

Taube’s main source for this contention is Dr. Robert Lustig, a specialist on pediatric hormone disorders and the leading expert in childhood obesity at the University of California, San Francisco School of Medicine. Lustig’s 2009 lecture called “Sugar: The Bitter Truth,” became a viral Internet sensation, having been viewed well over 800,000 times, which is astounding considering it is “a 90-minute discussion of the nuances of fructose biochemistry and human physiology.”

Lustig labeled sugar—in all its forms—as nothing short of poison, reserving special opprobrium for high-fructose corn syrup, which he called “the most dangerous additive known to man.”

By making such extreme claims, Lustig far surpasses the more conventional argument that sugar is nutritionally deficient, offering nothing but empty calories. He claims that the body metabolizes sugar differently than it does other carbohydrates, with deleterious metabolic consequences. In short, sugar taxes the liver, especially when it is consumed in liquid form such as soft drinks.

This, in turn, causes a phenomenon known as insulin resistance—in which your body’s cells ignore the action of insulin, which regulates blood sugar. Researchers have come to acknowledge insulin resistance as a catalyst for obesity, type 2 diabetes and many cancers—at least in laboratory rats. Some research has yielded results that seem to bear out Lustig’s thesis. One example is a 2010 study, published in the Journal of the American Medical Association, which found that people who consumed at least 25 percent of their daily calories from added sugars of any kind were 3.1 times more likely to have low levels of HDL-cholesterol (the good kind) in their bloodstream than people who consumed less than 5 percent of their calories from added sweeteners.

Lustig’s lecture also cited an historical correlation between increased societal sugar consumption and a rise in diabetes rates.

Not All Sugars Are Created Equal
The Times article has been greeted with a chorus of rebuttals, including an article in the The Huffington Post by Dr. David Katz, whose argument was based on human evolution. Katz stated that humans were born with a preference for sweets, that it has in fact “fostered the survival of the species,” because sweet foods, fruits in particular, were also more nutritious ones.

Kicking the Sugar Habit

Certainly, most people would likely benefit from reducing their consumption of sugar. Here are some quick and easy tips to offer clients who want to reduce their intake of sweets and, if necessary, kick the sugar habit:

  • Make better food choices. “Think about what you need to eat, not what you can’t eat next,” says Kleiner. Visit and input your height and weight. The site will tell you how much grains, fruits, vegetables and protein you should be consuming.
  • Eat more whole foods and make breakfast your largest meal and dinner your smallest.
  • Stop yo-yo dieting. “When did obesity become a problem? When people started dieting,” says Clark. “They think they have no will power when they get hungry, but hunger is a request for fuel, not a moral issue.”
  • Limit your total amount of daily calories from sugar. The U.S. Department of Agriculture’s 2010 Dietary Guidelines for Americans recommends that no more than 10 percent of total calories should come from added sugar. The American Heart Association suggests that women and men limit their sugar intake to 100 and 125 calories per day, respectively.

Numerous sources contacted for this story also disagreed, in whole or in part, with Lustig’s theory, for a variety of reasons.

While Dr. Susan Kleiner, owner of High Performance Nutrition on Mercer Island, Wash., and author of Power Eating, agrees that fructose has distinctive “fattening” properties and that Americans consume far more sugar than their ancestors, she contends that Lustig’s thesis was “too simple.” She added, “It’s a multifaceted issue, caused by highly processed foods, industrial food manufacturing and an overabundance of sugar.”

Kleiner adds that Lustig’s biochemistry is valid only up to a point. “We all consume fructose in the form of berries and honey, but healthy, active individuals who eat sugar don’t get fat. Our bodies are dynamic organisms, and the body responds to sugar in a variety of ways. It doesn’t help to demonize it.”

Dr. Catherine Jackson, chairwoman in the department of kinesiology at the University of California at Fresno, wrote in an e-mail message, “It would be hard to believe that a substance such as glucose, which is so fundamental to our production of energy at the cellular level, is toxic. We cannot produce ATP [adenosine-triphosphate, which transports chemical energy within cells for metabolism] without glucose. Both glucose and fructose are found in much of what we eat, but the way we metabolize them is different. Fructose takes a detour to the liver through the small intestine before it can be used, which is not the case for glucose. Also, not all of fructose metabolism is clearly understood.”

Several experts echoed Jackson’s critique about the distinctive ways the body processes different types of sugar. “From a biochemical standpoint,” explains Dr. Felicia D. Stoler, a nutrition and fitness consultant and author of Living Skinny in Fat Genes, “my brain knows the difference between glucose and fructose, but my pancreas, liver and small intestines don’t.”

Kleiner acknowledges that not just the biochemistry, but also the taste of fructose, is different from other sugars. “It’s sweeter, and manufacturers know that we’ve become adapted to it. Because they’re in competition, they can make foods sweeter and sweeter with almost no cost. Before high-fructose corn syrup, it was too expensive to put added sugar in everything.” As a result, our sugar consumption has doubled or tripled over the past 40 years or so. If people ate just as much sugar but it was composed of more glucose and less fructose corn syrup, whether it would be quite as metabolically disastrous is an open question.

Sugar Isn’t the Only Culprit
While we know that the pancreas will produce insulin in response to increasing blood sugar levels, explains Stoler, science isn’t sure if it may produce additional insulin in response to other sensory stimulation, such as a lack of physical activity or artificial sweeteners.

The latter is Stoler’s explanation of the obesity problem. “Non-nutritive sweeteners are the cause,” argues Stoler, “because the rise in obesity in the 1990s coincided with a rise in the consumption of artificial sweeteners. Artificial sweeteners are in so many foods, including products labeled ‘lower sugar,’ and they’re often not written on the labels by their brand names, which can confuse consumers.”

Conversely, consumers don’t realize how much natural sugar they’re consuming in fruits and vegetables. “People don’t know what to look for in food labels. Take 100 percent orange juice—the label will say it contains a certain number of grams of sugar, but that comes from fruit. Vegetables such as corn and peas are filled with sugar.”

Another theory posits an excess of dietary fats, cholesterol and their biochemical complications as the causes of obesity. Nancy Clark, a sports nutritionist in Boston and author of Nancy Clark’s Sports Nutrition Guidebook, says, “Blood vessels get inflamed from cholesterol plaque, which can trigger physiological states such as insulin resistance.”

The industrial food model and its reduction of necessary nutrients from the American diet also are cited as counter-arguments to Lustig’s focus on the sugar-obesity connection.

“We’re depleting our food supply and narrowing the scope of the foods we’re eating," explains Kleiner. "For example, we know that the fatty-acid composition of the animals we’re eating is wildly different from those of our forebears, and of free-range animals today. Same with the plant kingdom.”

Clark attributes the obesity dilemma—at least in part—to many peoples’ erratic eating schedules. “Whether they’re dieting or feel too busy to eat, they skimp on breakfast and lunch and when they get hungry and run up a caloric deficit, they crave sweets.”

Last, but certainly not least, the rise in obesity is also due to lifestyle changes wrought by technology and the nature of work. “We’ve engineered activity out of our lifestyle,” says Clark, “and there’s a lot more stress these days.”

Lustig’s methodology also has been criticized. Clark claims that a lot of research fingering sugar as a dietary villain doesn’t study its workings at normal levels in the body. “It also depends on what else you’re eating when you consume sugar,” she says. “A peanut-butter-and-jelly sandwich doesn’t have the same glycemic effect as a diet of Skittles. Plus, [studies such as the ones relied upon by Lustig] also don’t say if the animals being fed the sugar are exercising.”

Stoler believes that researchers miss a major piece of the puzzle by not doing hands-on work counseling patients, which can reveal important information about personal habits. “They rely only on other studies, and anyone can sift research to fit his argument."



Jim Gerard is an author, journalist, playwright and stand-up comic. He has written for the New Republic, Travel & Leisure, Maxim, Cosmopolitan, Washington Post, Salon, Details, New York Observer, and many other magazines. For more information, visit his site at

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