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Shiftwork and Weight Gain

Research suggests that shiftworkers might be more susceptible to weight gain than their daytime counterparts. In this article, we’ll examine what factors might be responsible for shiftworker weight gain and look at the potential benefits for employer’s to offer programs and services thatencourage employees to exercise and eat healthily.

Is there any link between shiftwork and weight gain?

A handful of studies have reported a link between shift work and weight/BMI gain. For example:

  • A 2000 study of 85 subjects working 8-hour shifts - 36 worked the day-shift and 49 worked late-shift (defined as evening or night shift) - found increase weight gain among the late-shift population. Since starting their shift, late-shift subjects had gained an average of 9.5 pounds, while the day-shift subjects in similar jobs had gained just two pounds (Geliebter et al., 2000).
  • A 2008 study that examined the BMI levels of 4,328 day workers and 2,926 shift workers (all male) at a Japanese steel company over a 14-year period (1991-2005) reported higher BMI levels among the shiftwork population. More specifically, 47.7% of shift workers compared to 39.6% of day workers had their BMI increase by 5% or more over the 14-year period (Suwazono et al., 2008).

What’s responsible for shiftworker weight gain?

A convergence of factors may help explain the link between shiftwork and weight gain, such as:

  1. Sleep Loss – Research has revealed that reduced sleep influences our appetite and hunger. Specifically, getting inadequate amounts of sleep alters the levels of hormones that regulate hunger, causing an increase in appetite and a preference for calorie-dense, high carbohydrate foods (Spiegel K et al., 2004). This can contribute to weight gain.

    Furthermore, research has found that sleep loss may interfere with the body’s ability to metabolize carbohydrates, resulting in high levels of glucose in the bloodstream. Excess blood glucose promotes overproduction of insulin — which, in turn, promotes the storage of body fat — and can also lead to insulin resistance, a precursor of adult-onset diabetes (Spiegel K et al., 2005). Some research has even shown that sleep loss can reduce the ability of fat cells to properly respond to insulin by as much as 30 percent (Broussard JL et al., 2012).
  2. Poor Diet – Many shiftworkers report not eating as well on the night shift as on the day shift. Often this can be partly attributed to limited food options on the night shift that consist of sugary vending machine options, microwave meals, or late-night food delivery restaurants.

    Furthermore, shiftworkers commonly report eating more since starting shiftwork. Whether it’s increased snacking to try and improve alertness on the night shift or even adding a 4th meal to their schedule, the increased calories can lead to weight gain.
  3. Lack of Regular Exercise – A key component of healthy weight management is regular exercise. However, CIRCADIAN data indicates that more than 40% of shiftworkers report not exercising at all and another 30% report exercising once a week or less. Working nights, rotating shifts, and long hours can make it challenging to find time to exercise.

What are the benefits of employer involvement?

You might be inclined to view weight gain and obesity as a personal matter and “none of your business” as an employer. But before you brush the issue aside, be sure to consider the benefits of employer involvement:

  •  Reduced Overtime. Obese workers take more sick-days than non-obese employees. A 2009 review of 36 studies that examined the relation between obesity status and sick leave found a clear trend of increased sick leave among obese employees. They found in the United States obese employees took an extra 1-3 days of absence compared with normal weight workers. And in Europe obese employees took extra days 10 of absence compared with normal weight workers (Neovius K et al., 2009).
  • Lower medical costs. Employees who weigh more, cost more: they incur more health care expenses and take more disability time. A 2012 study found that an obese person incurs medical costs that are $2,741 higher (in 2005 dollars) than if they were not obese (Cornell University, 2012).
  • Better-rested, more alert workers. Not only does carrying around extra weight drain energy, but also it can contribute to sleep apnea, a disorder characterized by interrupted breathing during sleep. Compared to healthy people, sleep apneics are several times as likely to suffer on-the-job alertness lapses and to cause automobile accidents due to falling asleep at the wheel.

What can employer’s do to address shiftwork weight gain?

While no employer ever has the right to force employees to exercise, employers can offer programs and services that make it easier for employees to exercise and eat healthily.

  1. Establish a company-wide wellness program.Many companies report great success with wellness programs that emphasize nutrition and exercise. For example, you can:
    • Offer on-site fitness facilities for employees or reimburse health-club dues.
    • Have on-site weight management programs. 
    • Hand-out pedometers. 
    • Sponsor company sports teams and walking clubs. 
  2. Stock vending machines with healthy food and water. This is especially valuable for night workers, who often have to depend on the vending machines for nighttime snacks. So when they face down a vending machine that is full of candy bars, chips and sugary drinks, it isn’t going to help them make healthy decisions.

    It doesn’t cost much to offer baked tortilla chips, fat-free Fig Newtons, low-fat pretzels and water in place of or alongside the standard potato chips, cupcakes and artificially-flavored soda. In fact, many vending machine companies deliver healthier, lower-fat snacks on request.

  3. Training & Education Materials. It's a good idea to train shiftworkers periodically on nutrition, exercise and how to get good sleep on a shiftwork schedule. Stress that even simple exercise, such as walking 30 minutes a day a few times a week, will help workers keep their weight down.


Cornell University. "Obesity accounts for 21 percent of U.S. health care costs, study finds." ScienceDaily, 9 Apr. 2012.¬ /releases/2012/04/120409103247.htm.

Geliebter A, et al. “Work-shift period and weight change.” Nutrition 2000; 16(1):27-9.

Neovius K, et al. “Obesity status and sick leave: a systematic review.” Obes Rev. 2009 Jan; (10(1):17-27.

Spiegel K et al. “Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite.” Annals of Internal Medicine, December 2004; 141(11):846-850.

Spiegel K et al. “Sleep loss: a novel risk factor for insulin resistance and Type 2 diabetes.” J Appl Physiol, 2005;(99):2008-2019.

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