Book: Fructose 'missing link' in obesity epidemic

Dr. Richard Johnson

Could the simple sugar responsible for putting the sweet in everything from bananas to root beer be the missing link in understanding what puts the fat on a person’s thighs? Yes, according to a book penned by a University of Florida researcher that was published today.

In his book, “The Sugar Fix: The High-Fructose Fallout That Is Making You Fat And Sick,” Richard Johnson, M.D., reviews the increasing evidence that fructose may play a role in the obesity epidemic and proposes a low-fructose diet he believes could help people lose weight and potentially prevent diabetes and cardiovascular disease.

“We recognize that obesity has multiple causes, including eating too much and exercising too little, but we think a missing piece of the obesity puzzle is fructose intake,” said Johnson, the J. Robert Cade professor of medicine and chief of the division of nephrology, hypertension and transplantation in the UF College of Medicine. “It’s not fructose itself that is the problem, but eating too much of it.”

Americans consume nearly three times as much fructose as a century ago, Johnson said. Although the major source of fructose is soft drinks, it’s found in a variety of foods such as fruit, juice, sweetened cereals and pastries.

“We think fructose makes you obese not simply by the calories it provides but because it also tricks hormonal systems that control appetite,” Johnson said. “You don’t get a sense of being full so you keep eating. It (fructose) may also be important in the development of diabetes, kidney disease and heart disease.

“An additional problem is that the more fructose you eat, the more sensitive you become to it,” Johnson said. “If you want to have success losing weight, you have to cut out fructose for two weeks. At that point you are no longer as sensitive and you can resume a low-fructose diet with ease.”

Johnson’s book, which was published by Rodale, contains a diet he developed with nutritionist and dietitian Elizabeth Gollub, Ph.D., as well as tables listing the fructose contents of common foods. Fructose content is not found on most labels.

Unlike other low-carbohydrate diets, which require dieters to reduce all carbs, Johnson’s plan targets fructose. Starchy foods like potatoes and rice aren’t a no-no as in low-carb diets. And after the first two weeks, dieters can resume eating fruit and having treats such as cake in moderation.

“Most people are used to eating about 50 percent of their diet as carbohydrates,” Johnson said “When you cut it way back and have a very high-protein, high-fat diet, it’s very hard to sustain. It’s also not necessarily healthy. What’s great about our diet is we can maintain a normal carbohydrate-protein-fat balance, and when you do that, the diet is much easier to sustain.”

Johnson became interested in fructose while studying hypertension. He and his colleagues discovered that uric acid increased blood pressure in animals and that ingesting fructose seemed to spur production of uric acid. Reducing uric acid in these animals helped control blood pressure and other problems such as pre-diabetes.

“The effect of fructose to cause pre-diabetes and raise blood pressure may be more important than its effects to increase weight,” Johnson said. “Our studies suggest that, even if one can control one’s weight, that excessive intake of fructose may increase the risk for high blood pressure and diabetes. Going on a low-fructose diet will have benefits above and beyond losing weight.”

The research in Johnson’s book came from studies in his own lab as well as from other scientists studying fructose in cells, animals and humans at other institutions, he said.

He also reviews the history of fructose consumption, comparing it with the rise of obesity. The two histories mirror each other, he writes.

Although fructose consumption was already on the rise when high-fructose corn syrup was invented, the introduction of this sweetener in the late 1960s accelerated the increase. High-fructose corn syrup contains about as much fructose as table sugar but is cheaper to produce, leading companies to produce bigger portions of sweets and soft drinks for the same price, Johnson said.

Today, Americans eat 30 percent more fructose than they did in the 1970s and three times as much as in 1900, when the obesity rate was 5 percent, Johnson said. About 33 percent of adults are now overweight or obese, according to the Centers for Disease Control and Prevention.

“After reading this book I found myself looking more carefully at labels, looking specifically for high-fructose corn syrup,” said Andrew Whelton, M.D., an adjunct professor of medicine and the former director of clinical nephrology at Johns Hopkins University. “I was amazed to see it so often.

“Although this book was put together for a lay audience, I thought it would be useful for health-care providers, particularly for anyone who deals with issues of obesity and diabetes.”