Being stressed out at work can make you fat, a new study suggests.

The more job strain men and women reported, the more likely they were to become obese, Dr. Eric J. Brunner of the Royal Free and University College London Medical School and colleagues found. Higher stress levels were also tied to excess fat around the middle, which is particularly harmful for health.

Chronic stress has been linked to heart disease and the metabolic syndrome, a constellation of symptoms including excess belly fat that increases the risk of diabetes and cardiovascular disease, Brunner and his team note. They hypothesized that job stress might make people more likely to develop obesity during adulthood as well.

To investigate, they followed 6,895 men and 3,413 women for 19 years. All were 35 to 55 years old at the study’s outset. Participants reported levels of job strain, defined as having heavy demands, little decision-making power, and little social support, at several points during the study.

Men and women who reported job strain on at least three occasions were 73 percent more likely to become obese than those who never said they were stressed on the job. They were also 61 percent more likely to develop central obesity, defined as a waist circumference greater than 102 cm (40 inches) for men or 88 cm (35 inches) for women.

Those who reported job strain on one occasion were at 17 percent increased risk of obesity and central obesity, while those who reported stress on two occasions were at 24 percent increased risk of obesity and 41 percent increased risk of central obesity.

Adjusting for factors that could be related to both job strain and obesity, such as socioeconomic status and cigarette smoking, reduced the relationship by only a small amount.

The findings provide “firm evidence that high psychological workload, together with lack of social support at work, acts as a causal factor for obesity,” Brunner and his colleagues conclude.

SOURCE: American Journal of Epidemiology, April 1, 2007.