If you think that going for a no-carb diet can keep you fit, then you need to think again, for a new study has found that table sugar does more harm than starchy foods such as bread, rice and potatoes.
Researchers at the University of Florida, who propose using new dietary guidelines based on fructose to gauge how healthy foods are, have called for dieters to put the new findings into practice.
"There's a fair amount of evidence that starch-based foods don't cause weight gain like sugar-based foods and don't cause the metabolic syndrome like sugar-based foods. Potatoes, pasta, rice may be relatively safe compared to table sugar. A fructose index may be a better way to assess the risk of carbohydrates related to obesity," said Dr. Richard Johnson, the senior author of the report, which reviewed several recent studies on fructose and obesity.
Many diets, including the low-carb variety, are based on the glycemic index, which measures how foods affect blood glucose levels. Because starches convert to glucose in the body, these diets tend to limit foods such as rice and potatoes.
Researchers said while table sugar is composed of both glucose and fructose, fructose seems to be the more dangerous part of the equation.
Johnson, the division chief of nephrology and J. Robert Cade professor of nephrology in the UF College of Medicine, said that eating too much fructose causes uric acid levels to spike, which can block the ability of insulin to regulate how body cells use and store sugar and other nutrients for energy, leading to obesity, metabolic syndrome and type 2 diabetes.
"Certainly we don't think fructose is the only cause of the obesity epidemic. Too many calories, too much junk food and too much high-fat food are also part of the problem. But we think that fructose may have the unique ability to induce insulin resistance and features of the metabolic syndrome that other foods don't do so easily," Johnson said.
Johnson said studies at other institutions have revealed that following a low-glycemic diet can reduce the risk for diabetes and heart disease, but the effect could occur because these dieters often are unintentionally limiting fructose as well by cutting out table sugar.
"Processed foods have a lot of sugar. Probably the biggest source (of fructose) is soft drinks," Johnson said.
Johnson also noted that, in relation to obesity, the type of fructose found in foods doesn't seem to matter. For example, the fructose in an apple is as problematic as the high-fructose corn syrup in soda. The apple is much more nutritious and contains far less sugar, but eating multiple apples in one sitting could send the body over the fructose edge.
Besides soft drinks, fructose can be found in pastries, ketchup, fruits, table sugar and jellies and in many processed foods, including the sugar substitute high fructose corn syrup.
Johnson said that researchers are planning to test a low-fructose diet in patients soon.
Kathleen Melanson, an associate professor of nutrition and food sciences at the University of Rhode Island, said establishing a fructose index for foods could "be an appropriate approach," depending on how foods are classified. It makes sense to limit foods prepared with high fructose corn syrup and table sugar, which often contain empty calories, but fruits are an important part of a person's diet.
"One concern I have always had with the glycemic index is the potential to pigeonhole foods as good or bad," she said.
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