Rat Research Links Low-Calorie Foods to Overeating
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Aug. 8, 2007 -- Diet sodas and other noncalorie and low-calorie foods may be contributing to the childhood obesity epidemic, new research suggests.
The studies involved young rats, not children, but researchers say the findings indicate that eating diet foods early in life may inadvertently lead to overeating and obesity later on.
Juvenile rats in the study fed sweet or salty low-calorie foods over time later overate when fed similar tasting calorie-dense foods, suggesting that the low-calorie foods disrupted the body's ability to recognize calories and regulate energy intake.
This was especially true among young rats genetically predisposed to become obese.
Researcher W. David Pierce, PhD, acknowledges that extrapolating the findings to human children is a big leap.
But the University of Alberta sociology professor says the rat studies may provide important clues about how early taste conditioning leads to overeating and obesity.
"Our findings suggest that in young children, diet foods may be a poor substitute for healthy foods with sufficient calories to meet energy needs," he tells WebMD.
Diet Foods and Obesity
The experiments involved 4-week-old juvenile and 8-week-old adolescent rats conditioned to associate particular tastes with caloric content.
This was done by feeding the animals either sweet or salty high-calorie or low-calorie gelatin cubes over the course of 16 days.
When the juvenile rats were later given energy-dense, pre-meal snacks with the same flavor as the low-calorie cubes, they ended up eating more regular food at meal time.
This was not the case with the older rats.
The study is published in the August issue of the journal Obesity.
The findings may help explain previous studies suggesting a link between diet soda consumption and obesity in children, Pierce and colleagues conclude.
"Data from our study indicate that the subversion of the relationship between taste and caloric content disrupts the normal physiological and behavioral energy balance of juvenile rats, resulting in overeating that is independent of genetic disposition for obesity," they wrote.
The American Beverage Association has said on multiple occasions that soft drinks and diet soft drinks do not cause weight gain. "All of our industry's beverages -- including regular or diet soft drinks -- can be part of a healthy way of life when consumed in moderation and as a part of a balanced lifestyle," they note in news statements.
Diet Expert Weighs In
Childhood obesity expert Goutham Rao, MD, says the rat studies may or may not give insights into how hunger cues relate to energy intake in young children.
Rao, the author of the book, Child Obesity: A Parent's Guide to a Fit, Trim and Happy Child, does agree that eating a healthy, well-balanced diet is better for young children than eating processed diet foods.
Rao directs the Center for Weight Management and Wellness at Children's Hospital of Pittsburgh.
"Parents often ask me if their children should drink diet sodas," he tells WebMD. "I tell them that diet soda is better than regular soda, but my preference would be water or low-fat milk."
He says soft drinks sweetened with sugar and other sugary beverages are among the biggest contributors to childhood obesity in the U.S.
"The solution to the obesity epidemic is simple to understand but hard to implement," he says. "Avoid sweetened beverages, avoid fast food, limit media time, fit physical activity into the everyday routine, and eat together as a family. If every family did these things there would be very few obese children."
SOURCES: Pierce, W.D. Obesity, August 2007; vol 15: pp 1969-1979. W. David Pierce, PhD, department of sociology, Alberta Institute of Human Nutrition, University of Alberta, Edmonton, Alberta, Canada. Goutham Rao, MD, clinical director, Center for Weight Management and Wellness, Children's Hospital of Pittsburgh; associate professor, University of Pittsburgh School of Medicine.
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