Weird Science: Sleep longer and you'll eat better

Sleep is considered a modifiable risk factor for various conditions, including obesity, with figures suggesting more than a third of Kiwis aren't getting enough sleep. Photo / 123RF

Sleeping for longer each night can help us eat healthier.

Sleep is considered a modifiable risk factor for various conditions including obesity and cardio-metabolic disease, with figures suggesting more than a third of Kiwis aren't getting enough sleep.

In a just-reported trial, researchers from King's College London looked at the feasibility of increasing sleep hours in adults who typically slept for less than the recommended minimum for adults of seven hours.

As well, they undertook a pilot investigation that looked at the impact of increasing sleep hours on nutrient intake.

They found that extending sleep patterns resulted in a 10g reduction in reported intake of free sugars compared to baseline levels.

The researchers also noticed trends for reduced intake of total carbohydrates reported by the sleep extension group.

"The fact that extending sleep led to a reduction in intake of free sugars, by which we mean the sugars that are added to foods by manufacturers or in cooking at home as well as sugars in honey, syrups and fruit juice, suggests that a simple change in lifestyle may really help people to consume healthier diets," study author Dr Wendy Hall said.

The 21 participants allocated to the sleep extension group undertook a 45-minute sleep consultation which aimed to extend their time in bed by up to 1.5 hours per night.

A further 21 control group participants received no intervention in their sleep patterns.

Each participant in the sleep extension group received a list with a minimum of four appropriate sleep hygiene behaviours that were personalised to their lifestyle - such as avoiding caffeine before bed time, establishing a relaxing routine and not going to bed too full or hungry - and a recommended bed time.

For seven days following the consultation, participants kept sleep and estimated food diaries and a wrist-worn motion sensor measured exactly how long participants were asleep for, as well as time spent in bed before falling asleep.

Eighty-six per cent of those who received sleep advice increased time spent in bed and half increased their sleep duration, ranging from 52 minutes to nearly 90 minutes.

Three participants achieved a weekly average within the recommended seven to nine hours.

"Our results also suggest that increasing time in bed for an hour or so longer may lead to healthier food choices," study leader Haya Al Khatib said.

"This further strengthens the link between short sleep and poorer quality diets that has already been observed by previous studies."

Why do women live longer?

Women today tend to live longer than men almost everywhere worldwide - in some countries by more than a decade. Photo / 123RF

Women today tend to live longer than men almost everywhere worldwide - in some countries by more than a decade.

In New Zealand, life expectancy at birth was 83.2 years for females and 79.5 years for males, based on death rates between 2012 and 2014.

Now, three centuries of historical records show that women don't just outlive men in normal times: they're more likely to survive even in the worst of circumstances, such as famines and epidemics, authors of a new study say.

Most of the life expectancy gender gap was due to a female survival advantage in infancy rather than adulthood, the researchers found.

In times of adversity, newborn girls are more likely to survive.

The fact that women have an edge in infancy, when behavioural differences between the sexes are minimal, supported the idea that explanation was at least partly biological.

The international team of researchers analysed mortality data going back roughly 250 years for people whose lives were cut short by famine, disease or other misfortunes.

The data spanned seven populations in which the life expectancy for one or both sexes was a dismal 20 years or less.

Among them were working and former slaves in Trinidad and the United States in the early 1800s, famine victims in Sweden, Ireland and the Ukraine in the 18th, 19th and 20th centuries, and Icelanders affected by the 1846 and 1882 measles epidemics.

In Liberia, for example, freed American slaves who relocated to the West African country in the 1800s experienced the highest mortality rates ever recorded.

More than 40 percent died during their first year, presumably wiped out by tropical diseases they had little resistance to.

Babies born during that time rarely made it past their second birthday.

Another group of people living in Ireland in the 1840s famously starved when a potato blight caused widespread crop failure.

Life expectancy plummeted by more than 15 years.

Overall, the researchers discovered that, even when mortality was very high for both sexes, women still lived longer than men by six months to almost four years on average.

Girls born during the famine that struck Ukraine in 1933, for example, lived to 10.85, and boys to 7.3 - a 50 per cent difference.

When the researchers broke the results down by age group, they found that most of the female survival advantage comes from differences in infant mortality.

Newborn girls were hardier than newborn boys.

The results suggested that the life expectancy gender gap couldn't be fully explained by behavioural and social differences between the sexes, such as risk-taking or violence.
Instead, the female advantage in times of crisis may be largely due to biological factors such as genetics or hormones.

Estrogens, for example, have been shown to enhance the body's immune defences against infectious disease.

"Our results add another piece to the puzzle of gender differences in survival," the researchers reported.

On Earth, we all have the same shot at survival

All of Earth's 8 million species - from large whales to tiny organisms - have an equal shot at existence, researchers say. Photo / 123RF

There are more than 8 million species of living things on Earth, but none of them - from 24m blue whales to microscopic bacteria - has an advantage over the others in the universal struggle for existence.

UK and US scientists have described the dynamic that began with the origin of life on Earth four billion years ago, and report that regardless of vastly different body size, location and life history, most plant, animal and microbial species are equally "fit" in the struggle for existence.

This was because each transmitted approximately the same amount of energy over its lifetime to produce the next generation of its species.

"This means that each elephant or blue whale contributes no more energy per gram of parent to the next generation than a trout or even a bacterium," said study co-author Dr Charles A.S. Hall, a systems ecologist at New York's College of Environmental Science and Forestry.

"We found, rather astonishingly, by examining the production rate and the generation time of thousands of plants, animals and microbes that each would pass on, on average, the same amount of energy to the next generation per gram of parent, regardless of size.

"A single-celled aquatic alga recreates its own body mass in one day, but lives for only a day.

A large female elephant takes years to produce her first baby, and lives much longer than the alga.

"For all plants and animals of all sizes these two factors - rate of biomass production and generation time - exactly balance each other, so each contributes the same energy per gram of parent to the next generation in their lifetime."

The bottom line, Hall said, was that all organisms are, on average, equally fit for survival.

"The fact that all organisms are nearly equally fit has profound implications for the evolution and persistence of life on Earth," said study co-author Dr James H. Brown, of the University of New Mexico.