Intensive bouts of exercise can lead to significant and progressive decline in sleep quality, says a new study.

The researchers also found that a high carbohydrate regime reduces some, but not all, of the effects of hard training.

For the study, the scientists from Loughborough University in England studied the effects of two nine-day periods of heavy training on 13 highly trained cyclists.

The researchers monitored the athletes' moods, sleep patterns and performance before, during and after exercise.

To determine whether diets could counter the effects of any sleep deprivation, the athletes were also given high or moderate amounts of carbohydrate throughout the study, though none of them knew which.

The researchers discovered that even as little as nine days of intense training can cause 'significant and progressive decline in sleep quality'.

"Sleep efficiency was significantly reduced during the intensified training period," the researchers observed, with the number of times the athletes woke throughout the night significantly increased.

They also noticed that the athletes' moods and capacity for exercise both worsened over the period of observation.

As for the additional carbohydrates, the team concluded that a high carbohydrate regime reduced some, but not all, of the effects of hard training.

The study appeared in the Journal of Sports Sciences.

Adolescence is a time when many children may consider experimenting with alcohol or drugs. A new research shows parents can reduce that risk by maintaining a healthy and open relationship with their children.

"Adolescents are more likely to drink or use drugs if they hang out with deviant friends or if they actively seek out peers to facilitate substance use," said study's lead author Thomas Schofield from Iowa State University in the US.

"Parents who know what's going on with their children and their friends can minimize the impact of both pathways," Schofield added.

Nearly 675 children were included in the study.

Researchers observed mothers and fathers separately as they interacted with their children in fifth grade and again in seventh grade.

Their data shows that for many, this age range is a starting point or baseline for alcohol, tobacco and drug use. It's also a time when parents may be caught off guard by changes in their child's behaviour, if they don't have a strong foundation established, Schofield said.

He added: "Preadolescence and early adolescence is not a particularly risky time; it's just the best time to get kids on board with collaborating, communicating with their parents and creating that relationship earlier."

This indicates that more than genetics is at play, and parents can make a difference in influencing their child's behaviour, Schofield said.

Are you a green tea lover? Read this carefully as the cup packed with anti-oxidants and other health benefits may adversely affect your fertility and development in case of frequent use, warn researchers.

In experiments over fruit flies, the team from University of California-Irvine discovered that excessive consumption adversely affected development and reproduction in fruit fly populations.

According to them, one should avoid high dose of green tea or any natural product as nutraceuticals such as green tea, while growing in popularity, are largely unregulated.

"While green tea could have health benefits at low doses, our study and others have shown that at high doses, it may have adverse effects," said Mahtab Jafari, associate professor of pharmaceutical sciences.

"Further work is needed to make any definite recommendations but we suggest that green tea should be consumed in moderation," she added.

For the study, Jafari and colleagues investigated the effects of green tea toxicity on the development and reproduction in fruit fly Drosophila melanogaster.

Embryos and larvae were subjected to various doses of green tea polyphenols.

Larvae exposed to 10 milligrams of green tea were slower to develop, were born smaller and exhibited a dramatic decline in the number of emerged offspring.

Ten milligrams of green tea made the flies more susceptible to starvation and heat stress but protected them against dehydration.

Female offspring showed decreased reproductive output and a 17 percent reduction in lifespan while males were unaffected, the study found.

Ten milligrams of green tea caused morphological abnormalities in reproductive organs such as testicular and ovarian atrophy.

Jafari believes that high doses of green tea may cause "too much" apoptosis or cell death.

Derived from the plant Camellia sinensis, green tea is popular worldwide for its purported brain and heart health and anti-cancer properties.

Jafari noted that in other tests with mice and dogs, green tea compounds in large amounts dramatically reduced body weight and, in mice, negatively affected embryo development.

"We are planning to measure total consumption and identify and quantify the metabolites of natural products in flies," Jafari pointed out, adding that these experiments will enable us to have a better understanding of toxic doses in humans.

The paper appeared in the Journal of Functional Foods.

Reducing the size of large food portions, packaging and tableware could help tackle obesity, a new Cambridge study has claimed.

Researchers have found the 'most conclusive evidence to date' that people consume more food or drinks from larger size portions or packages, and when using larger items of tableware.

The study at the University of Cambridge in UK found that eliminating larger portions completely could reduce daily energy intake consumed by 12 per cent to 16 per cent among adults in the UK, and by 22 per cent to 29 per cent among adults in US.

Researchers suggested steps like reducing food and drink serving sizes that contain high amounts of calories such as the standard single serving of confectionery, chips and cakes, and reducing availability of larger portion and package sizes.

They said that portion sizes should be limited at check outs, aisle ends and special displays. They also called for highlighting single portion sizes in packaging.

According to the researchers, implementation of portion size interventions will be easier in public sector organisations, such as schools, hospitals, military bases, and prisons, than in industries.

They said that reducing portion sizes may mean going back to sizes of portion and tableware similar to those in the 1950s, and changes may even involve reductions of over 50 per cent for some energy dense products.

This is far greater than the estimated 5 per cent reductions currently offered and negotiated with the food industry.

The study was published in The BMJ.

Exploring sexual identity, sexual attraction and sexual arousal in women, new research shows that heterosexual women have more diverse patterns of sexual response than previously reported.

In the first study, women watched short videos, and in the second study, women listened to stories about interacting sexually with a woman or a man.

Genital response was measured with a vaginal photoplethysmograph - a clear acrylic device that illuminates the capillary bed of the vaginal wall -- and participants also self-reported their sexual arousal.

In both studies, the lead researcher Meredith Chivers from the Sexuality and Gender Laboratory at Queen's University showed that only heterosexual women who were exclusively attracted to men showed similar genital responses to both female and male sexual stimuli.

Heterosexual women who also report some attraction to women, however, showed a different pattern of response - their genital responses were greater to female stimuli, similar to other sexually-diverse women.

"Both exclusively and predominantly androphilic women (women attracted to men) showed sexual response patterns that differed from their self-reported sexual attractions," Dr Chivers noted.

"Sexually-diverse women showed genital and self-reported arousal responses that were more similar to their self-reported sexual attractions," she noted.

As a whole, this research illustrates the complex relationship between sexual identity, sexual attraction, sexual arousal and genital responses to sexual stimuli.

Earlier research on women's sexual orientation and patterns of sexual response has previously focused on women's genital and subjective sexual arousal relative to their sexual identity, as heterosexual, bisexual or lesbian.

Among women, however, there is significant diversity among women in their sexual attractions to other women and men, regardless of sexual identity.

For example, a substantial minority of heterosexual women (20 per cent in some studies) also report some attraction to women.

"The new research provides a window of opportunity to understand how women's sexual response relates to her experience of sexual attraction and desire, addressing gaps in contemporary models of sexual response," concluded Dr Chivers in the journal PLOS ONE.