Relationship of obesity to job stress and eating behavior in male Japanese workers

Abstract

Objective:

To examine a possible relationship between obesity, job stress, and eating behavior in male Japanese workers.

Method:

A questionnaire on life style, job stress, and eating behavior was conducted with 208 male workers aged 19–60 years (33.7±12.3 years) in a manufacturing industry in Japan. Height and weight were measured in an annual health examination. The relation between obesity, job stress, and eating behavior were analyzed between 141 nonobese subjects (BMI 24.9 kg/m2) and 67 obese subjects (BMI 25.0 kg/m2).

Results:

Obesity was associated with psychological stress responses of tension/anxiety, especially tension. Tension/anxiety was also related to job demands positively and job latitudes negatively. The eating behaviors of subjects with tension/anxiety resembled those of the obese subjects.

Conclusions:

The present study suggests that obese male Japanese workers tend to be in a stressful state from high job demands and low job latitudes in the workplace. Such stressful conditions may affect eating behaviors to eat much and contribute to obesity. Stress management might be necessary in the workplace for the prevention of obesity among male Japanese workers.

Introduction

Obesity is known to be a health problem leading to diabetes mellitus, hypertension, and hyperlipidemia, and to heart disease and stroke.1, 2, 3 According to the WHO criteria, BMI of 25 kg/m2 or more and less than 30 kg/m2 indicates overweight, and BMI of 30 kg/m2 or more obesity.4 On the other hand, it has been realized that the WHO's criteria for obesity should be different for various ethnic groups.5 In Japan, the prevalence of the obesity-related diseases was shown to increase with BMI even lower than 30 kg/m2,2, 6 and hence the Japan Society of the Study of Obesity has adopted BMI of 25 kg/m2 and more as a criteria for obesity.7 According to the National Nutrition Survey 2000 in Japan about 30% of males aged 30–60 years had a BMI of 25 kg/m2 or more. This is an increase of about 1.5-fold over the past 20 years for all age groups in men. Males of 30–60 years are usually a working population. Hence, obesity is an important health problem among male Japanese workers.

With the rapid globalization and technological innovation in the workplace, job stress is also a health problem, which is reportedly associated with cardiovascular disease.8, 9 Job stress may contribute to obesity.10 With male workers, Netterstrøm et al.11 showed a significant association between BMI and job strain. In contrast, Kornitzer and Kittel,12 Steptoe et al.13 and Jönsson et al.14 did not find significant associations between BMI and psychological job stress in men. Thus, earlier findings about the relationship between obesity and job stress were inconsistent.10 It is also indicated that job stress may influence eating behavior to lead to obesity.15 Work-related stress is reported to be associated with an increased intake of fatty foods,16, 17, 18 which will lead to obesity.19

In the present study, we conducted a questionnaire survey to clarify the relation between obesity, job stress, and eating behavior in male Japanese workers.

Methods

Study subjects

The subjects were all 214 male employees of a synthetic fiber-manufacturing plant. Self-completed questionnaire forms were distributed to these 214 men at the end of April 2003 and collected in May from those who consented to participate. After the questionnaires were collected, they were checked for completeness by an occupational health nurse. Questionnaires were collected from 210 men, for a response rate of 98.1%. Two of the respondents with a history of mental disorders under treatment were excluded; the present analysis was thus conducted with the remaining 208 men aged 19–60 years (mean age±s.d.; 33.7±12.3 years).

Body mass index (BMI; kg/m2) was calculated from the results of the annual health examinations conducted from March to May 2003 in the manufacturing plant. Based on the criteria of the Japan Society for the Study of Obesity, obesity was defined as a BMI 25 kg/m2 in this study, though it is classified as overweight and obesity according to the WHO criteria; the 208 subjects were divided into a nonobese group (141 subjects with BMI 24.9 kg/m2) and an obese group (67 subjects with BMI 25.0 kg/m2).

Contents of questionnaire survey

Basic attributes and life style

The survey asked about age, sex, work pattern, job type, overtime working hours, walking time during commute, average sleeping time, health state, regular exercise, smoking habit, alcohol consumption, and so on.

Job stress

The Job Stress Questionnaire,20 which was made in a study commissioned by the Japanese Ministry of Health, Labor and Welfare, was used in the present study. The Questionnaire has been shown to have Cronbach α coefficient of 0.74 for job stress factors, 0.84 for psychological stress response, 0.81 for physical stress response and 0.83 for support.20 The questionnaire consists of three main parts of job stress factors of psychological workload, psychological stress response, and stress mitigation factors.

The questions have a total of 17 items to measure job stress factors of psychological workload (Table 1). These are categorized as quantitative workload (1–3), qualitative workload (4–6), physical workload (7), job latitude (8–10), application of technology (11), interpersonal conflict (12–14), workplace environment (15), and appropriateness of work (16, 17). The section on psychological stress response (Table 2) has a total of 18 items to measure positive responses (activity (1–3)) and negative responses (anger (4–6), fatigue (7–9), tension/anxiety (10–12), and depression (13–18)). The section to assess physical stress response (Table 2) has a total of 11 items. Stress mitigation factors were measured by nine items incorporating support in the family and workplace and two items on satisfaction with workplace and family.

Table 1 Items of job stress factors in the Job Stress Questionnaire
Table 2 Items of psychological and physical stress responses in the Job Stress Questionnaire

The respective scores for psychological and physical stress responses are then totalled and assessed. Each item was rated on a four-point scale ranging from ‘strongly disagree’ to ‘strongly agree.’ Subjects with a psychological stress response score of 51 points or more are considered to have a high mental stress response. Similarly, persons with a total score for physical stress response of 25 points or more are considered to have a high physical stress response.

Eating behavior

Of the 50 items on the Sakata's Eating Behavior Questionnaire, thirty questions (Table 3) were used that have been shown to differ significantly between obesity patients and healthy people.21, 22 This questionnaire is used in some hospitals for obesity treatment in Japan.23 These 30 questions are classified into the seven areas regarding cognition of constitution (1–3), eating style (4–6), eating rhythm abnormalities (7, 8, 16, 17, 30), feeling of satiety (9, 10, 24, 25, 28), substitute eating and drinking (11, 18, 19, 21–23), meal contents (12–15, 20), and motivation for eating (26, 27, 29).

Table 3 Items of eating behaviors in the Sakata's Eating Behavior Questionnaire

Statistical analysis

The relationship between obesity, job stress, and eating behavior in the obese and nonobese groups was investigated as follows. The χ2 test and Mann–Whitney U-test were used for basic attributes, life style, job stress, and eating behavior. The relation between obesity and each category of job stress factors, stress responses and eating behaviors was investigated with a logistic regression analysis after adjusting for age. The relation between psychological stress response and each category of job stress factors and eating behaviors was also investigated using the Spearman's correlation coefficient. All statistical analyses were completed with the statistical package SPSS 11.5J.

Results

Basic attributes and life style

Mean age was significantly higher in the obese group (36.0±12.2 years) than in the nonobese group (32.6±12.2 years), while working pattern, type of job, hours of overtime work, exercise, or smoking or drinking habits were not different between the two groups (Table 4).

Table 4 Characteristics of obese and nonobese subjects

Job stress

Job stress factors

Since there was a significant difference in age between the obese and nonobese subjects, logistic regression analyses for relations between obesity and job stress factors were conducted while considering age. The results showed no significant relation between obesity and job stress factors (Table 5).

Table 5 Age-adjusted OR and 95% CI between obesity and job stress factors

Psychological and physical stress response

Subjects with a total of 51 points or more for mental stress response accounted for 9.2% of the nonobese group and 10.4% of the obese group. Subjects with 25 points or more for physical stress response accounted for 10.6% of the nonobese group and 19.4% of the obese group. There were no significant differences between the two groups.

The results of each category about psychological and physical stress response were shown in Table 6. A significant association was found in a psychological stress response category of ‘Tension/Anxiety’ (odds ratio (OR) 1.22; 95% confidence interval (CI) 1.05–1.42, P=0.008). Associations between obesity and the respective item for category of ‘Tension/Anxiety’ were shown in ‘be tense’ (OR 1.88; 95% CI 1.31–2.70, P=0.001), ‘be anxious’ (OR 1.25; 95% CI 0.88–1.76, P=0.213) and ‘be unsettled’ (OR 1.40; 95% CI 0.96–2.07, P=0.085). Physical stress response did not show a significant association with obesity (Table 6).

Table 6 Age-adjusted OR and 95 % CI between obesity, psychological and physical stress responses

Correlation between job stress factors and psychological stress response

Since a significant relation was found between obesity and the psychological stress response category of ‘Tension/Anxiety,’ an association between the stress response of ‘Tension/Anxiety’ and job stress factors was examined using the Spearman's correlation coefficient. ‘Tension/Anxiety’ was positively correlated with job stress factors related to job demand of quantitative and qualitative workload, and interpersonal conflict (P<0.01, Table 7). ‘Tension/Anxiety’ was also negatively associated with job latitude (P<0.01).

Table 7 Spearman's correlation coefficients between psychological stress response (Tension/Anxiety) and job stress factors

Eating behavior

Relation between obesity and eating behavior

An age-adjusted logistic regression analysis was conducted to investigate a relation between obesity and eating behaviors. As shown in Table 8, significant OR over 1.2 were encountered in the category of ‘Cognition of constitution’ (OR 1.95; 95% CI 1.61–2.36, P<0.001), ‘Feeling of satiety’ (OR 1.28; 95% CI 1.15–1.42, P<0.001), ‘Substitute eating and drinking’ (OR 1.23; 95% CI 1.11–1.37, P<0.001). Significant OR over 2 were encountered in the items of ‘I tend to gain weight more easily than others’ (OR 6.32; 95% CI 3.88–10.30, P<0.001) and ‘I gain weight just by drinking water’ (OR 2.90; 95% CI 1.99–4.22, P<0.001) in the category of ‘Cognition of constitution,’ and ‘I feel regret after eating too much’ (OR 2.82; 95% CI 1.93–4.13, P<0.001) and ‘I am often cautioned by others about overeating’ (OR 2.45; 95% CI 1.64–3.65, P<0.001) in the category of ‘Feeling of satiety,’ and ‘I eat to get rid of irritability’ (OR 3.10; 95% CI 1.93–4.98, P<0.001) in the category of ‘Substitute eating and drinking.’

Table 8 Age-adjusted OR and 95% CI between obesity and eating behaviors

Correlation between eating behavior and psychological stress response

A possible relation between the psychological stress response of ‘Tension/Anxiety’ and eating behaviors was also investigated using the Spearman's correlation coefficient. The results are given in Table 9. A positive correlation (r>0.2) with ‘Tension/Anxiety’ was found in the category such as ‘Eating style,’ ‘Feeling of satiety,’ ‘Cognition of constitution,’ ‘Motivation for eating.’ All these categories corresponded with eating behaviors for which a significant correlation was encountered in the obese group.

Table 9 Spearman's correlation coefficients between psychological stress response (Tension/Anxiety) and eating behaviors

Discussion

The present study showed that obese male Japanese workers tended to be in a stressful state associated with high job demands and low job latitudes in the workplace. Obesity was not directly associated with psychological workload factors such as high job demands and/or low job latitudes, which was generally in accordance with previous studies showing little evidence for an association between BMI and psychological workload.10 However, the present study indicated that obesity was closely associated with the psychological stress response of ‘Tension/Anxiety.’ This survey also showed that ‘Tension/Anxiety’ was associated with the psychological workload factors reflecting high job demands and low job latitudes. Such work-related tension/anxiety may contribute to obesity among male Japanese workers.

Job-related stress is thought to be associated with diseases such as heart disease and hypertension.8, 9 In the ‘job demands-control model’ proposed by Karasek,24 high stress responses and health problems are likely to occur when the workers have high demands and low latitudes over the work.25, 26 In the present study no association was found between obesity and psychological workload factors. The reviewed articles by Overgarrd et al.10 also mentioned that no evidence between BMI and psychological workload was generally found for men. However, this study showed a significant association between obesity and the psychological stress response of ‘Tension/Anxiety.’ In addition, the tension/anxiety was related with high job demands and low job latitudes. Thus, the present findings seems to be in accordance with Karasek model, suggesting that high job demands and low job latitudes are likely to bring on tension among male workers, which may contribute to obesity. Interpersonal conflict might be related to incorporating support.

In Western countries factory workers reportedly tended to have greater BMI than management workers, whereas in Japan management workers, office workers, engineers, and sedentary job workers tended to have greater BMI.27, 28 Shift work has also been shown to be associated with BMI.27 In addition, obesity was found to be greater in unemployed males and males living alone.17 In the present study, no significant differences were found in relation to job kind or position, or shift work.

It is suggested that stress may influence eating, resulting in either eating or not eating, and that women are more prone to stress-induced eating than men.15 Men may react to stress by increasing alcohol use.29 The present study showed that eating behaviors of workers having ‘Tension/Anxiety’ under job stress resembled those of obese persons. The category related to obesity such as ‘Eating style,’ ‘Feeling of satiety,’ ‘Cognition of constitution,’ ‘Motivation for eating’ suggest that workers feeling stressed are prone to eat much. It is, hence, supposed that work-related tension may affect eating behaviors to eat much and result in obesity. Some studies have also reported that number of meals, skipping breakfast, and eating out are associated with obesity.30, 31 However, no relation was found with skipping breakfast or eating out in this study.

The present study showed that obese male Japanese workers tended to be in a stressful state, which could be associated with high job demands and low job latitudes. Such stressful conditions may affect eating behaviors to eat much and subsequently contribute to obesity among male workers. To avoid overeating from stress, stress management might be required in the workplace. The present study was a cross-sectional study of a small number of male workers in one workplace of a manufacturing industry in Japan. These results could be specific to that study condition. Future studies are needed to get conclusive results.

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Acknowledgements

This study was conducted with aid for the health promotion field from a medical research and health promotion activities grant for 2002 from the Aichi Health Promotion Foundation.

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Correspondence to H Sakakibara.

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Nishitani, N., Sakakibara, H. Relationship of obesity to job stress and eating behavior in male Japanese workers. Int J Obes 30, 528–533 (2006). https://doi.org/10.1038/sj.ijo.0803153

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Keywords

  • BMI
  • job stress
  • eating behavior
  • tension

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