New research suggests that the amount of control you have at your job could have an effect on your waistline.

Australian researchers found that having skills and the freedom to use them at work is linked to lower body mass index (BMI) and smaller waist size, whereas needing to make a lot of decisions is linked to bigger waist size.

In 2014, more than 1.9 billion adults worldwide were overweight; of these, more than 600 million were obese. One area of interest for researchers has been how the kinds of work people do, and their experience of their work, can contribute to obesity.

"Many people point to 'eating too much and not moving enough' as the cause of obesity," Christopher Bean, lead author of the study and a health psychology PhD candidate from the University of Adelaide, said in a statement. "While this might explain how weight gain often happens, it does not acknowledge things such as environmental, psychological, social or cultural factors -- these are some of the important why reasons that obesity happens."

Control at a job can come in two broad forms: skill discretion -- having and being able to apply skills -- and decision authority. Traditionally, increasing an employee's level of job control has been seen as a good thing and the two factors have been considered together when looking at their effect on people's health. However, the new study suggests that the two aspects of job control should be considered separately in terms of their effects on health, and obesity in particular.

For the study, researchers collected and analyzed data from more than 400 middle-aged adults who worked in a variety of different occupations, both blue and white collar. They measured participants' height, weight and waist circumference in a clinic and conducted telephone interviews to collect information about their work. They used a model called the Job Demand-Control-Support (JDCS) model to assess the psychosocial qualities of their work.

Researchers found that skill discretion and decision authority, when examined separately, were comparatively strongly associated with obesity, with surprisingly opposite effects.

"When looking at the wide system of factors that cause and maintain obesity, work stress is just a small part of a very large and tangled network of interactive factors," Bean said. "On the other hand, work is a fundamental part of life for many, so it is important to find innovative ways of extending our understanding of how factors at work may be implicated in the development and maintenance of obesity. It is important to challenge the status quo and explore unexpected or counter-intuitive findings with curiosity."

The findings are detailed in the journal Social Science & Medicine.