Why fast foods are bad, even in moderation

Why fast foods are bad, even in moderation

   * 21:30 12 June 2006
   * NewScientist.com news service
   * Anna Gosline

SEating a diet consisting largely of fast food could cause your waistline to bulge more than eating the same amount of fat from healthier sources.

Monkeys fed a diet rich in trans-fats – commonly found in fast foods – grew bigger bellies than those fed a diet rich in unsaturated fats, but containing the same overall number of calories. They also developed signs of insulin resistance, which is an early indicator of diabetes.

Trans-fats, or partially hydrogenated oils, are found in many fast foods and also in baked goods and processed snacks. They dramatically increase the risk of heart disease – even more than saturated fats found in animal products.

Kylie Kavanagh, at Wake Forest University Baptist Medical Center in Winston-Salem, North Carolina, US, wondered how this “killer fat” would affect the risk of diabetes in 51 vervet monkeys.

She fed one group of monkeys a diet where 8% of their daily calories came from trans-fats and another 27% came from other fats. This is comparable to people who eat a lot of fried food, says Kavanagh. A different group of monkeys was fed the same diet, but the trans-fats were substituted for mono-unsaturated fats, found in olive oil, for example.

Both groups ate the same total calories, which were carefully metered to be just enough for subsistence. Path to diabetes

After six years on the diet, the trans-fat-fed monkeys had gained 7.2% of their body weight, compared to just 1.8% in the unsaturated group. CT scans also revealed that the trans-fat monkeys carried 30% more abdominal fat, which is risk factor for diabetes and heart disease.

“We were shocked. Despite all our enormous efforts to make sure they didn’t gain weight, they still did. And most of that weight ended up on their tummies,” says Kavanagh, who presented her findings at the American Diabetes Association meeting in Washington DC, on Monday. “This is walking them straight down the path to diabetes.”

This is the first study to show such a dramatic result on abdominal fat, adds Dariush Mozaffarian at the Harvard School of Public Health in Boston, US. “The days of thinking about fats just as calories are over,” he says.

Partially hydrogenated oils can easily be replaced by other oils during food production. Last week, fast-food giant Wendy’s announced that it was cutting partially hydrogenated oils from its food in the US and Canada, while in January, food manufacturers in US were ordered to label all trans-fats on packaged goods.