Many dieters may actually be cutting out the wrong foods, according to a University of Florida study that suggests that dieters should focus on limiting the amount of fructose they eat, instead of cutting out starchy foods such as bread and rice.
"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," said researcher Dr. Richard Johnson. "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."
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.
While table sugar is composed of both glucose and fructose, fructose seems to be the more dangerous part of the equation, the study notes. 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," Johnson said. "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."
Other studies have shown 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, Johnson said. "Processed foods have a lot of sugar," Johnson said. "Probably the biggest source [of fructose] is soft drinks."
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.
"One of the things we have learned is this whole epidemic brought on by Western diet and culture tracks back to the 1800s," Johnson noted. "Nowadays, fructose and high-fructose corn syrup are in everything."
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Source: University of Florida