Workers who regularly pull overnight shifts may be more prone to weight gain, a new analysis suggests.
The finding involved an in-depth look at 28 studies conducted between 1999 and 2016.
All the investigations explored the health impact of shift work, in which employees are regularly asked to either alternate between daytime and overnight schedules or to exclusively work overnight hours.
Sleep disruption the main culprit
An estimated 700 million men and women around the world now follow that work pattern, representing about 20% of the global workforce, the researchers said.
And while the numbers varied by study, the new analysis determined that, on average, routinely working a night shift seems to boost the risk for becoming obese or overweight by 29%.
Connie Diekman, director of university nutrition at Washington University in St Louis, suggested that sleep disruption is without question the main culprit.
"As studies have demonstrated, and this study supports, the human body is programmed to sleep when it is dark, allowing hormones that impact hunger and satiety to reset for the next day," she explained.
"When people are awake when they should be sleeping, the hormones related to hunger and satiety appear to be thrown off, resulting in changes in eating, changes in metabolism and a tendency to eat more than we need," Diekman said.
The investigators reported their findings in the issue of Obesity Reviews.
Alarm bells for health
That particular finding could ring public health alarm bells, given that abdominal fat has long been associated with metabolic syndrome. The syndrome includes high blood pressure, high cholesterol and high triglyceride levels, and it drives up the risk for developing heart disease, diabetes and stroke.
What's more, less than 3% of these workers adapted their sleep schedules to accommodate night-time work, suggesting that many were likely not getting a sufficient amount of sleep on a routine basis.
"This [has] an impact on the circadian rhythm," said Diekman, referring to everyone's natural 24-hour internal sleep clock.
Exercise and a healthy diet
Night shifts also challenge a worker's ability to access good food and exercise regularly, noted Kris-Etherton.
One solution, she said, is to "bring healthy foods and snacks to the workplace to eat".
Advanced planning is key, agreed Diekman. "Preparing dishes ahead of time is an easy way to have better options," she said.
"If your workplace does not offer good options or if you only have vending machines, think about better food choices that you could carry, and then how those choices can pair with what is available onsite," Diekman suggested.
"And, of course, remember that if you can get more movement into your workday it will help you with energy levels and possibly weight," Diekman added.
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