The mouse-data findings, published in Nature’s Scientific Reports, suggest that consumption fructose causes significant weight gain, physical inactivity, and body fat deposition compared to a calorie-matched amount of glucose.
Led by Catarina Rendeiro at the Beckman Institute for Advanced Science and Technology, the team studied two groups of mice for two-and-a-half months: one group was fed a diet in which 18% of the calories came from fructose - mimicking the intake of adolescents in the United States - and the other was fed 18% from glucose.
“The present study suggests that fructose per se, in the absence of excess energy intake, increases fat deposition and body wight potentially by reducing physical activity, without impacting hippocampal neurogenesis or cognitive function,” concludedRendeiro and her colleagues.
Fructose in the firing line?
The fresh findings come after previous reports suggested that fructose consumption in particular is a ‘key driver’ of type 2 diabetes risk, and may be more harmful to a number of key health measures - including mortality and fertility - than consumption of sugar in the form of sucrose.
These reposts, coupled with data that demonstrates the increasing prevalence of fructose in foods and drinks may be linked with a greater proportion of total caloric intake and increasing obesity, has led to increased focus on the role fructose plays in metabolism.
“Nonetheless, despite the parallel increase in obesity and levels of fructose intake, the specific contribution of this monosaccharide to overweight and obesity in the population remains debatable,” said the authors.
"The reality is that people are not only consuming more fructose through their diets, but also consuming more calories in general,” said Rendeiro. "One of the key questions is whether an increase in fructose intake contributes to obesity in the absence of excessive calorie intake.”
Rendeiro and her colleagues examined the impact of a fructose diet relative to an isocaloric glucose diet in the absence of overfeeding, using a mouse model that mimics fructose intake in the top percentile of the USA population (18% energy).
“The important thing to note is that animals in both experimental groups had the usual intake of calories for a mouse," said Rendeiro. "They were not eating more than they should, and both groups had exactly the same amount of calories deriving from sugar, the only difference was the type of sugar, either fructose or glucose."
Following 77 days of supplementation, changes in body weight (BW), body fat, physical activity, cognitive performance and adult hippocampal neurogenesis were assessed.
Despite the fact that no differences in calorie intake were observed between groups, the fructose animals displayed significantly increased BW, liver mass and fat mass in comparison to the glucose group, the authors reported.
“This was further accompanied by a significant reduction in physical activity in the fructose animals,” they said.
"We don't know why animals move less when in the fructose diet," commented senior author Professor Justin Rhodes. "However, we estimated that the reduction in physical activity could account for most of the weight gain."
According to Jonathan Min, a study co-author, biochemical factors could also begin to explain how the mice respond to the high fructose diet.
“We know that contrary to glucose, fructose bypasses certain metabolic steps that result in an increase in fat formation, especially in adipose tissue and liver,” he said.
Source: Scientific Reports
Published online ahead of print, doi: 10.1038/srep09589
“Fructose decreases physical activity and increases body fat without affecting hippocampal neurogenesis and learning relative to an isocaloric glucose diet”
Authors: Catarina Rendeiro, et al