Saying it was ready to put them on supermarket shelves, a British company announced recently that it had harvested its first commercial crop of tomatoes designed through genetic engineering not to rot.

The announcement by British drugs firm Zeneca Group Plc means that Britons will become the first European consumers to sample genetically altered food when the tomatoes, grown in California, go on sale as paste early next year through the Safeway and J. Sainsbury Plc supermarket chains.

The tomatoes have been genetically altered to slow down the action of a rotting enzyme called polygalacturonase so as to prolong the life of the fruit.

Zeneca is growing 17 acres of the crop in California for the British market with each acre producing about seven to eight tonnes of paste from an average of 30,000 plants.

The tomatoes are the only genetically altered whole food to be allowed on sale in Britain, but other food stuffs such as rapeseed oil, for use as cooking and salad oil, and soybean extracts have also been given the go-ahead.

Some environmentalists have expressed concern about growing genetically engineered foods and say such crops could pose long-term dangers to humans and the environment.

The environmental group Greenpeace believes that they might trigger new food allergies, while their cultivation could cause "genetic pollution'' if they cross-pollinate with conventional crops or weeds.

Zeneca says the tomatoes are safe to consumers and the paste produced from them will carry labels telling customers that it was grown from genetically engineered plants.

Despite environmentalist concerns, such foodstuffs may become commonplace in a few years time. Many other firms are working in the area and Zeneca is developing a rot-resistant banana tree.

*** According to new US data, meanwhile, the number of overweight children has more than doubled in the past 30 years, particularly in the last decade.

"It's consistent with what we see in adults. It's a big pattern,'' said Richard P. Troiano, an epidemiologist with the US National Centre for Health Statistics in Hyattsville, Maryland, part of the federal Centres for Disease Control and Prevention.

About 4.7 million youngsters aged six through 17 years are overweight, Troiano and his team reported in the October issue of the Archives of Paediatrics & Adolescent Medicine, published by the American Medical Association. The findings also were presented this week at a science writer's conference in Miami Beach, Florida.

According to the data, the proportion of overweight children jumped from five percent in 1963-65, the first years of the survey, to 10.9 percent in 1988-91, the most recent years.

"And most of that increase,'' Troiano told the Associated Press in a weekend telephone interview, "is in about the last 10 to 12 years.'' Overweight, of course, is harder to define in children than in adults because no one is sure how much weight is healthy and how much is ominous during various stages of children's growth, Troiano said.

But heavy children will tend to become heavy grownups who are at increased risk for gallbladder disease, osteoarthritis, diabetes, heart disease, some cancers and early death.

The researchers defined overweight using what they said is a clear-cut and extreme standard -- the 95th percentile of body mass index, a weight-to-height calculation.

The research team also attributed the increase in overweight children to a combination of increased calorie intake and decreased exercise.