Sleep more to slim down, scientists say
PARIS (AFP) — An extra hour between the sheets at night might be the key to shedding excess weight and fighting obesity, according to recent research.
"More sleep could be the ideal way of stabilising weight or slimming," said neuro-scientist Karine Spiegel, of France's INSERM, a public organisation dedicated to biological, medical and public health research.
While poor eating habits and lack of exercise clearly play a role in the global rise of obesity, recent data indicates that lack of sleep may also be a factor, and one that is often under-estimated.
Around 30 surveys carried out on wide population samples in seven countries have underlined a link between lack of sleep and excess weight or obesity in both children and adults, Spiegel said.
The first of the studies, carried out in 1992 in France, highlighted the problem in children and teenagers. Spiegel said the increase in obesity in the US in the second half of the 20th century corresponded with a mounting decrease in sleep.
Two key hormones produced at night which help regulate appetite were at play, she said.
Grehlin makes people hungry, slows metabolism and decreases the body's ability to burn body fat, and leptin, a protein hormone produced by fatty tissue, regulates fat storage.
"We have shown that less sleep (two four-hour nights) caused an 18 percent loss of appetite-cutting leptin and a 28 percent increase of appetite-causing grehlin," she said.
Such hormonal changes made people hungry for foods heavy in fats and sugars such as chips, biscuits, cakes and peanuts, she added.
The sleep loss caused a 23 to 24 percent increase in hunger, Spiegel said, translating into an extra 350 to 500 kilocalories a day, "which for a young sedentary adult of normal weight could lead to a major amount of added weight."
It was unclear whether several years of sleep deprivation could lastingly harm the body's ability to restore a balance between the two hormones.
A study released in Washington in February showed children lacking shut-eye faced a greater risk of becoming obese than kids who got a good night's sleep.
Each extra hour of sleep cuts a child's risk of becoming overweight or obese by nine percent, according to an analysis of epidemiological studies by researchers from Johns Hopkins Bloomberg School of Public Health.
By contrast, children who got the least sleep had a 92 percent higher chance of being overweight or obese than children who slept enough, said the study published in the journal Obesity.
"Our analysis of the data shows a clear association between sleep duration and the risk for overweight or obesity in children. The risk declined with more sleep," said Youfa Wang, a senior author of the study.
"Desirable sleep behavior may be an important low cost means for preventing childhood obesity and should be considered in future intervention studies," Wang said in a news release.
The researchers reviewed 17 published studies on sleep duration and childhood obesity.
Some research recommends that children under five years old sleep 11 hours or more a day, while children age five to 10 should get 10 or more hours of sleep, and children older than 10 should sleep at least nine hours.
AB de Villiers cracked a maiden double-century as South Africa pummelled the Indian attack in the second Test here on Friday, leaving the tourists in a virtually unassailable position.
De Villiers (217 not out) was not alone in feasting on a mediocre Indian attack, with Jacques Kallis's solid 132 helping South Africa reach 494-7 at stumps on the second day in reply to India's paltry 76.
Paul Harris was the other not out batsman, on nine, when rain stopped play with 12.4 overs remaining of the day's play.
Kallis and De Villiers put on 256 for the fifth wicket, South Africa's best stand for any wicket against India in Tests. The previous highest was 236 between openers Gary Kirsten and Andrew Hudson at Kolkata in 1996.
De Villiers and Kallis exposed India's bowling limitations with 83 runs coming in the first session and 107 in the second for the loss of just one wicket.
India's needed early wickets after the visitors resumed at 223-4, but none of their five specialist bowlers could maintain pressure on Kallis and De Villiers.
The 24-year-old De Villiers outscored his senior partner and was the first to reach his hundred, scooping a Sourav Ganguly delivery to the fine leg boundary.
He surpassed his previous best of 178 (against West Indies at Bridgetown in 2005) when he swung off-spinner Harbhajan Singh over mid-wicket for a six that landed on the roof of the stand.
De Villiers completed his double-century in the closing session when he drove Harbhajan for a four. It was his fifth three-figure knock in Tests and his first against India.
His score was also the best by a South African batsman against India in Tests, surpassing Herschelle Gibbs's 196 at Port Elizabeth in 2001.
It was a demoralising day for India, who grabbed just one wicket in the first two sessions as Kallis and De Villiers tightened the screw.
When Kallis inside-edged paceman Shanthakumaran Sreesanth's delivery on to his stumps in the afternoon session, South Africa were a mammoth 297 runs ahead with five wickets in hand.
The 32-year-old Kallis surpassed Australian batting legend Don Bradman's tally of 29 centuries during his 275-ball innings containing a six and 14 fours.
India's Sachin Tendulkar holds the world record of 39 Test hundreds, followed by Australian Ricky Ponting (34), India's Sunil Gavaskar (34), West Indian Brian Lara (34), Australians Steve Waugh (32) and Matthew Hayden (30), and Kallis (30).
Kallis also completed his hundred in style, fluently driving Ganguly through the covers for a four in the post-lunch session.
He had a narrow escape on 61 when the ball rolled on to the stumps but did not dislodge the bails.
India took the second new ball in the first session in a bid to snap the partnership after spinners Harbhajan and Anil Kumble had failed to provide the breakthrough.
The opening Test of the three-match series ended in a draw in Chennai. The final match begins in Kanpur on April 11.
