The Globe and Mail: Sleep the weight off

The Globe and Mail: Sleep the weight off

By André Picard

Want to lose some weight? Try hitting the snooze button next time the alarm clock rings.New research suggests that rising levels of obesity are due, at least in part, to chronic sleep deprivation, which is endemic in the work-obsessed Western world.
Two new studies, published today, show that too little sleep can lead to higher levels of a hormone that triggers appetite, and lower levels of a hormone that tells your body it's full and has enough fuel.

The result: The less you sleep, the more you eat -- and the more weight you gain.

"Our results demonstrate an important relationship between sleep and metabolic hormones," said Dr. Shahrad Taheri, clinical lecturer in endocrinology at Bristol University in Bristol, England.

"In Western societies, where chronic sleep restriction is common and food is widely available, changes in appetite-regulatory hormones with sleep curtailment may contribute to obesity."

In the paper, published in the medical journal Public Library of Science Medicine, researchers speculate that sleep loss has an impact on several hormones related to appetite and food intake. They said two such hormones -- ghrelin and leptin -- are thought to play a role in the interaction between short sleep-duration and high body-mass index (an approximation of body fat based on height and weight).

Ghrelin, which is primarily produced by the stomach, triggers appetite in humans: The more ghrelin you have, the more you want to eat.

Leptin, a hormone produced by fat cells, tells the body that its energy stocks are low and that there is a need to consume more calories. Low leptin levels are a signal for starvation and increased appetite.

Dr. Taheri and his colleagues found that people who normally slept for five hours nightly produced 14.9 per cent more ghrelin than those who slept for eight hours. They also produced 15.5 per cent less leptin. The results held regardless of gender, eating patterns or exercise habits.

"It was quite amazing that a hormone can track a person's self-reported amount of sleep so well," said Dr. Emmanuel Mignot, an associate professor of psychiatry and behavioural sciences at Stanford University in Palo Alto, Calif., and a co-author of the study. "The effect must be very strong to appear in [this entire] population," he said.

Dr. Mignot said while the link between hunger hormones and sleep has been demonstrated before in the lab, this is the first time the correlation has been demonstrated in a large number of people in the general population.

The research was conducted on 1,024 volunteers from the Wisconsin Sleep Cohort, a long-term study of people with sleep disorders that began in 1989.

Participants, who were aged 30 to 60, underwent nocturnal polysomnography (a test during which a number of physiologic variables are measured and recorded during sleep), and blood sampling once every four years. They also reported on their sleep habits every five years through questionnaires and six-day sleep diaries.

According to background material in the research paper, during the past 50 years the time people spend sleeping has dropped an average of two hours a night because of increasing demands, pressures (work, school, family), and the availability of new technologies (television, computer games and the Internet).

A second, unrelated study, published in today's edition of the Annals of Internal Medicine, also found a link between sleep and hunger hormones. Researchers at the University of Chicago took 12 healthy young men and allowed them to sleep only four hours nightly.

The result, after only two nights of sleep deprivation, was a 28-per-cent increase in ghrelin and an 18-per-cent drop in leptin. In addition, participants reported not only being hungrier, but craving calorie-dense, high-carbohydrate foods such as chips and cookies.

About 48 per cent of Canadian adults are overweight, according to Statistics Canada.