| The most common nutritional disorders in the United States and much of the developed world are overweight and obesity. Fructose from the consumption of sucrose and high fructose corn syrup (primarily in sweetened beverages) has come to comprise a significant proportion of energy intake in the American diet and the increase of fructose consumption coincides with the marked increase in the prevalence of obesity over the past two decades. Fructose feeding induces insulin resistance, impaired glucose tolerance, hyperinsulinemia, hypertriglyceridemia, and hypertension in experimental animals. This work explores whether fructose consumption might be a contributing factor to the development of obesity and the accompanying metabolic abnormalities observed in the insulin resistance (metabolic) syndrome in humans. Unlike glucose, fructose infusion in monkeys does not stimulate insulin and leptin secretion. Since insulin and leptin function as key signals to the central nervous system in the long-term regulation of energy balance, decreases of circulating insulin and leptin could lead to increased energy intake and thereby contribute to weight gain and obesity during long-term consumption of diets high in energy derived from fructose. In a short-term study conducted in normal weight pre-menopausal women, postprandial insulin and leptin concentrations were lower over a 24-hour period in which three high fructose (30% of energy) meals were consumed compared to three high glucose meals. In addition, the circulating triglycerides were markedly increased on the high fructose day compared to the high glucose day. In a longer-term study conducted in overweight postmenopausal women, 14-hour postprandial circulating glucose, insulin and leptin concentrations were reduced after 10 weeks of fructose compared to glucose consumption. Consuming dietary fructose did not induce measurable insulin resistance or increased blood pressure in the subjects; however, postprandial triglycerides were increased when compared to subjects consuming the same amount of energy (25%) as glucose. The observed effects of fructose on insulin, leptin and triglycerides suggest that long-term consumption of diets high in fructose, along with high-fat diets and inactivity, could contribute to weight gain, obesity, and cardiovascular disease. Additional comprehensive, long-term studies are needed to investigate this possibility, particularly in persons at risk for metabolic disease. |
