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22-02-2012 | Dietetics | Article

Bodyweight rise with fructose ‘may be due to excess calories’


Free abstract

MedWire News: Fructose does not appear to induce weight gain per se, conclude Canadian and US researchers who suggest that excess calories may be to blame for previous associations between intake of the sugar and weight gain.

Consumption of fructose in Western diets has increased in recent years and has been linked to the epidemics of overweight, obesity, and diabetes. However, while ecologic analyses, observational studies, and controlled-feeding trials have suggested a positive association between high-fructose corn syrup consumption and weight gain, uncertainties remain.

To investigate further, David Jenkins (University of Toronto, Ontario, Canada) and colleagues conducted a systematic review and meta-analysis of controlled-feeding trials examining the effect of fructose on bodyweight in both isocaloric and hypercaloric conditions. Studies involving high-fructose corn syrup were excluded.

In all, 32 reports that detailed 31 isocaloric and 10 hypercaloric feeding trials, involving a total of 756 individuals, were selected for analysis. The studies typically enrolled fewer than 15 participants, lasted for less than 12 weeks, and were of low quality. The mean fructose dose was 69.1 g/dL, representing 17% of energy, in the isocaloric trials, compared with 182 g/dL, representing 37.5% of energy, in the hypercaloric trials.

The results, published in the Annals of Internal Medicine, indicated that fructose had no overall impact on bodyweight in isocaloric trials, at a mean difference in bodyweight for fructose compared with nonfructose carbohydrate of -0.14 kg. Interestingly, significant weight loss was observed with fructose in the five trials that enrolled overweight/obese individuals, at a mean difference in bodyweight of -0.55 kg.

By contrast, the high doses of fructose in hypercaloric trials led to significant increases in bodyweight, at a mean difference of 0.53 kg with fructose. The significance of the effect of fructose on bodyweight was not eliminated in more conservative analyses.

The researchers write: "Aggregate data analyses of controlled feeding trials do not support a bodyweight-increasing effect of fructose in isocaloric exchange for other sources of carbohydrate in the diet.

"However, evidence indicates that added fructose providing excess energy at extreme levels of intake may have a bodyweight-increasing effect over the short term, although confounding from excess energy cannot be excluded."

By Liam Davenport