一提到减肥,大家很自然就会想到节食. 可是美国最新研究表明,少量摄入碳水化合物的同时多吃些富含蛋白质和脂肪的食物同样可以让人再现苗条. 您有勇气试试吗?
科技界又传来令人振奋的消息,克隆领域取得突破性进展. 这究竟对人类是喜还是忧?
Edited by Kent

Meat support



The claimed benefits of the controversial low-carbohydrate Atkins diet have been reaffirmed in two new studies, one of which is the longest study to date.

"I think it's good news for Atkins dieters," says Linda Stern, who led the first study of 132 obese patients at the Veterans Affairs Medical Center in Philadelphia, US.

The diet was devised by the late US doctor Robert Atkins. To lose weight, devotees avoid carbohydrates and consume more protein and fat instead.

Both new studies carried out in 2004 found that subjects on the Atkins diet shed significant amounts of weight without harmful effects on blood fats and sugars. But the studies have failed to silence critics of the diet, who want the US government to investigate alleged adverse effects.

Stern's year-long study was twice the length of any previous study. Half the patients followed the Atkins regime, limiting daily carbohydrate intake to just 30 grams. The rest tried losing weight through a conventional low-fat diet much richer in carbohydrates.

By the end, both groups had lost about the same amount of weight, between five and eight kilograms for the Atkins group and three to eight kilos for the low fat group. However, the Atkins dieters lost almost all their weight in the first six months, then remained at a steady weight.

"But what we really need is a study showing whether people on the low-carbohydrate diet for years have different odds of heart attacks, strokes and diabetes," she says.

A second, six-month study on 120 overweight patients at Duke University Medical Center in Durham, North Carolina, shows low-carbohydrate dieters shedding an average of 12 kilos, twice that lost by those on a low-fat regime. And the pattern of blood fats and sugars mirrored that in Stern's study.

"Over six months, the diet appears to be relatively safe, but we need to study the safety for longer durations," says Will Yancy, head of the Duke team. Implying that the diet seems safe enough in the short term but long-term effects are still unknown.

 

 

Breakthrough in human cloning



Scientists, in 2004 demonstrated for the first time that therapeutic cloning in humans can be achieved.

The researchers in South Korea created 30 cloned embryos that grew to about 100 cells in size -further than any verified experiment so far. They further showed that the embryonic stem cells could develop into a variety of tissue types.

Their long-term hope is that such a procedure would provide a source of perfectly matched transplant tissue for the treatment of diseases such as diabetes and Parkinson's disease.

"In this precise moment there is a person in South Korea walking around with [embryonic] stem cells tailor-made for her," says Jose Cibelli from Michigan State University. He is the only US researcher involved with the work.

"It is a great piece of work," Cibelli says. Cloning in primates even has been regarded as especially challenging and perhaps even impossible.

However, several scientists expressed concern that the proof now published by the Koreans might assist maverick scientists in attempting to clone a baby. The scientific consensus is that this would be far too risky.

The vast majority of nations support a global ban on cloning babies, but attempts at the United Nations to implement one have stalled. This is because some countries, including the US, want therapeutic cloning banned too, as it involves the destruction of embryos.

The key difficulty researchers had anticipated in cloning humans or other primates relates to chemical factors that assist cell division.

Unlike eggs from other species, primate eggs have cell division factors that are lost when the nucleus is removed from the egg-the first step of cloning. Some scientists argued that this would doom any chance of yielding healthy embryos.

Usually there is a very low success rate for human embryo cloning. So why did cloning work for the South Koreans? Nobody knows the answer yet, but techniques such as using a much gentler method to extract the cells' nuclei may have helped.

 

 

Barbie, very fertile



Large-breasted, narrow-waisted women have the highest reproductive potential, according to a new study carried out in 2004, suggesting western men's penchant for women with an hourglass shape may have some biological justification.

Women with a relatively low waist-to-hip ratio and large breasts had about 30 per cent higher levels of the female reproductive hormone estradiol than women with other combinations of body shapes, found Grazyna Jasienska and her team at Jagiellonian University in Krakow, Poland.

"If there are 30 per cent higher levels, it means they are roughly three times more likely to get pregnant," said Jasienska, a human biologist.

"In Western societies, the cultural icon of Barbie as a symbol of female beauty seems to have some biological grounding," concludes the team.

The team studied 119 Polish women aged 24 to 37, who were not taking any kind of hormonal contraception or medication. Women who were extremely underweight or overweight were not included.

Saliva samples taken from the women revealed that those with narrow waists and large breasts had on average 26 per cent higher levels of the hormone estradiol, than women of other shapes.

Waist-to-hip ratio also had a strong effect on levels of another female hormone, progesterone. Jasienska, says that higher progesterone levels should also theoretically translate to increased fertility. However, large breast size was not significantly related to increased progesterone.

Jasienska says that a preference for low waist-to-hip ratios is a "universal feature" in psychological studies of men. "It was interesting to see that what we observed in psychological studies has some biological background," she says.

Vocabulary
controversial 有争议的
carbohydrate 碳水化合物
regime 政权
duration 持续时间
therapeutic 治疗的
embryonic 胚胎的
diabetes 糖尿病
consensus 共识