If you’ve ever sat at your desk scarfing a vending-machine lunch, then you’d probably agree with the authors of a recent editorial in the journal PLoS Medicine, who wrote: “[U]nhealthy eating could legitimately be considered a new form of occupational hazard.”
The authors are referring mainly to night-shift workers — doctors and nurses, for instance — who work in 24/7 industries. Off-kilter shift schedules are notorious for encouraging bad eating habits, and they also disrupt circadian rhythms and prevent adequate sleep — all of which conspires to make workers fat and increase their risk of Type 2 diabetes, among other ills.
The editorial writers cite the results of a recent study, also published in PLoS Medicine, and which we reported on Healthland earlier this month, that involved nearly 177,000 participants of the Nurses’ Health Studies. That study found that women who had rotating night shifts were more likely to develop diabetes over a 20-year follow-up, compared with women who worked during the day.
The longer women worked nights, the higher their risk: those who had rotating night shifts for 1 to 2 years had a 5% increased risk of diabetes; working nights on and off for 10 to 19 years upped the risk to 40%; and women who pulled graveyard shifts for more than 20 years were 60% more likely to develop diabetes than those who never worked at night.
The study authors, led by Dr. Frank Hu, a professor of nutrition and epidemiology at Harvard School of Public Health, had multiple theories for why night work might lead to bad health. For one thing, shift workers are more likely to grab junky foods on the go — out of the aforementioned vending machines or from fast-food restaurants — which leads to weight gain, a risk factor for diabetes. They’re also less likely to get regular exercise, because of their screwy sleep schedules.
Previous research has shown that even going to bed mere hours later than normal — at 3:45 a.m., instead of 12:30 a.m. — can lead to unhealthy eating and weight gain. We reported on a study by Northwestern University Feinberg School of Medicine researchers in May:
Being a night owl appeared to do more harm than good: for starters, people who stayed up late got less sleep overall (5 hrs. 33 mins. versus 6 hrs. 38 mins. for normal sleepers). Worse, compared with early-to-bed-early-to-risers, late sleepers had a much less healthful diet: they ate more fast food (five meals per week, compared with the normal sleepers’ three), drank more full-calorie soda (4.5 servings per week versus 1.3) and got significantly fewer fruits and vegetables (1.9 servings per day versus 3.4).
Notably, the late sleepers ate roughly the same number of calories per day as normal sleepers. … However, they ate a larger proportion of their food later in the day — at dinner or after 8 p.m. On average, late sleepers’ dinners contained 825 calories, while the normal sleepers’ suppers totaled 630 calories. Those who stayed up late consumed 754 calories per day after 8 p.m., while the normal sleepers ate only 376 calories.
The findings fall in line with animal research on the same phenomenon. A 2010 study found that when light-dark cycles were tampered with, so that mice were exposed to continuously dim light when they should have been sleeping, mice gained 50% more weight than animals living in a natural light-dark environment, even though all the mice ate and exercised the same amount.
Turns out, the animals exposed to late-night light — equivalent to the glow of a TV or computer screen for humans — ate most of their food during their normal sleeping hours, suggesting that it’s not only what you eat, but when that matters.
Further, disrupted sleep itself — either not getting enough sleep or sleeping at the wrong time — interferes with your circadian rhythm, which may in turn wreak havoc with your appetite and metabolism, and increase blood sugar levels and insulin resistance, according to Hu. These factors also increase risks for obesity and diabetes.
The problem of shift work is no small matter: some 15% to 20% of the working population in the U.S. and Europe is engaged in night work. “As the world of work becomes increasingly 24 hour, shift work will become more common,” the editorial authors write, suggesting that it “has the potential to accelerate the progression of the global epidemic of obesity and diabetes.”
There may not be much to mitigate the effects of shift work — especially if it’s inconsistent — on the body’s internal clock, but workers’ eating habits are “obvious targets for intervention,” the authors note. Perhaps workplaces, particularly those that employ shift workers, can lead the way in improving workers’ diets and making sure it’s easier and cheaper for them to eat healthily than not, the authors said.
Many heroic efforts to change people’s eating behaviors have been launched and failed over the years, but the authors suggest that the field of occupational health now has reason to enter the fray.