Work Stress and Obesity

1. Work Stress and Obesity Dr. BongKyoo Choi Center for Occupational and Environmental Health University of California, Irvine Session 5: Work & Health April 28, 2009

2. Goals To understand the seriousness of current obesity epidemic/pandemic To figure out the role of work stress in the current obesity epidemic/pandemic

3. Outline • Definition, measures, and risk of obesity • Recent obesity statistics • Limitations of exercise and low caloric intake • Work stressors and obesity • A theoretical model (possible mechanisms) for work stress and obesity

4. Definition and measures of obesity • “a condition of abnormal or excessive fat accumulation in adipose tissue to the extent that health may be impaired” Field anthropometric methods • Body Mass Index (BMI, kg/m2): r = 0.7-0.8 with body fat % • Waist circumference: central obesity (40 inches for men and 35 inches for women) • Skinfold thickness

5. Classification of overweight and obesity in adults according to BMI (WHO, 1998)

6. Limitations of BMI (Prentice and Jebb, 2001)

7. Risk of Obesity (WHO, 1998) • Relative risk, ≥ 3 Type 2 diabetes, Insulin resistance Gallbladder disease Dyslipidemia, Sleep apnea and respiratory problems • Relative risk, 2-3 Coronary heart disease, Hypertension Osteoarthritis (knees), Gout • Relative risk, 1-2 Menstrual irregularities and infertility, Some cancers (endometrial, breast, and colon), Low back pain

9. OECD 2009

11. Obesity Trends* Among U.S. AdultsBRFSS,1990, 1998, 2006 (*BMI 30, or about 30 lbs. overweight for 5’4” person) 1998 1990 2006 No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% ≥30%

12. National center for health statistics(November. 2007) • More than one-third of U.S. adults -– over 72 million people -- were obese in 2005-2006: 33.3 percent of men and 35.3 percent of women. • Adults aged 40 - 74 had the highest obesity prevalence compared with other age groups • Approximately 53 percent of non-Hispanic black women and 51 percent of Mexican-American women aged 40-59 were obese compared with about 39 percent of non-Hispanic white women of the same age.

14. Contributing factors (according to CDC) • Overweight and obesity result from an energy imbalance. This involves eating too many calories and not getting enough physical activity.  • Body weight is the result of genes, metabolism, behavior, environment, culture, and socioeconomic status.  • Behavior and environment play a large role causing people to be overweight and obese. These are the greatest areas for prevention and treatment actions.

15. Empirical evidence from the NIH(the effects of diet on weight loss in the overweight/obese) • Low-Calorie Diets (1,000-1,200 Kcal/day)

16. RCT Empirical evidence from the NIH(the effects of exercise on weight loss in the overweight/obese) • Moderate/vigorous Physical activity

20. Contributing factors (according to CDC) • Overweight and obesity result from an energy imbalance. This involves eating too many calories and not getting enough physical activity.  • Body weight is the result of genes, metabolism, behavior, environment, culture, and socioeconomic status.  • Behavior and environment play a large role causing people to be overweight and obese. These are the greatest areas for prevention and treatment actions. • Role of work?Another place for increasing physical activity?

21. Work-related risk factors for obesity • Shift work: Gelieber et al., 2000; Morikawa et al., 2007; Ramsey et al., 2009; van Amelsvoort et al., 1999; Yamada et al., 2001 • Long working hours per week: Shields, 1999 • Low job control: Kivimaki et al., 2006 • High job strain: Kivimaki et al., 2006; Ishizaki et al., 2008 • Low social support at work/isostrain: Brunner et al., 2007

22. Work-related risk factors for unhealthy behaviors • Fast-eating behaviors/stress-induced overeating: High job demands(Nishitani et al., 2009; Choi and Schnall et al., 2009a); Low social support and isostrain(Brunner et al., 2007; Choi and Schnall et al., 2009a); and Shift work(Choi and Schnall et al., 2009a) • Non-active leisure-time physical activity: Passive jobs (low job control and low job demands) and long working hours(Choi and Schnall et al., 2009b)

24. Macro-level changes of our work since 1980s • Technology (automation) • Work organization (Taylorism to lean production) • Decreased rates of unionization • Service-driven society • Globalization - 24/7/365 society • Neo-liberalism – “Washington consensus” • Social inequality

25. Washington consensus • John William (1989) coined… • A standard package of economic policies promoted by the IMF, World Bank, and US Treasury Department • International/domestic financial market liberalization • Trade liberalization (particularly in developing countries) • Labor market “flexibility” • Legal security of property rights • Privatization of publicly-owned assets • Deregulation: market friendly • Taxation: shifts taxes from capital to labor • etc.

26. Micro-level changes of our work since 1980s • Sedentary work • High/Low work intensity • Long/short working hours • Precarious work/temporary work • “Inflexible” work schedule: shift work • Low control • Lack of reciprocity (new psychological contract) • Income inequality

27. Some US statistics • Decreased sleep-time: more than 30% of the US adults report sleeping less than 6 hr/night (Knutson et al., 2007) • Increased female employment rate: 55.4 % (1980) to 65.9 % (2007) • Increased working hours for women/family: combined couple work time: 551 hrs between 1970 and 2000 (Jacob and Gerson, 2004) • Increased work intensity : 40-45 s/min in traditional production; 57 s/min in new lean production system (Alder et al., 1997) • Increased job strain: big increase in job demands and relatively small increase in job control – (Landsbergis et al., 1999) • Decreased unionization rates: 28.3 % (1954) to 11.5% (2003): Mayer (2004) • Widen income inequality:see the next slide • Increased work-and-family imbalance • Increased contingent workers (part-time, temporary, and contract): 25.8 % (1980) to 35.1 % (1988): Sweeney and Nussbaum 1989. VS. Decreased fat intake Slightly increased (or same-level) leisure-time physical activity Decreased smoking rate

28. Income inequality (OECD, 2009)

29. MIDUS II: Work stress – Active Leisure-time physical activity

30. MIDUS II: Work stress – Stress-Induced Overeating

31. Work Stress – Burned-Out Hypothalamus?

32. The physiological roles of hypothalamus • Linked to limbic system, midbrain, lower CNS, & pituitary • Involved in hunger, satiety, and feeding behavior • Autonomic nerve systems • Endocrine systems (- pituitary-adrenals): cortisol and GH/sex hormones • Interactions with leptin (from Greek word, “thin”), synthesized and secreted from adipose tissue; a long-term fat metabolism • Control of body temperature • Sleep (circadian rhythm) – suprachiasmatic nucleus

34. Hypothalamic arousal(Bjorntorp et al., 1999) • “The origin of essential hypertension is found in central regulatory mechanisms, activating both the sympathetic nervous system and the HPA axis in an ‘hypothalamic arousal syndrome’ (Diabetic Medicine, p. 379) • “It is thus clear that when the HPA axis is functioning normally, there is associated evidence of excellent health in anthropometric, hormonal, metabolic and haemodynamic variables” (Diabetic Medicine, p. 375)

37. The role of sympathetic nerve system on obesity? • β1 , β2 , and β3: lypolysis vs. α2: inhibit lypolysis • Cortisol must be present for the lypolysis effect of catecholamines • Catecholaminergic modulation of CRH and ACTH secretion (Plotsky et al., 1989) • Sympathetic control of white adipose in lean and obese (Dodt et al., 2003): “a profound unresponsiveness of subcutaneous adipose tissue to neurally induced lypolysis in obese female subjects”

38. Hunger Fact: Internationalhttp://www.bread.org/learn/hunger-basics/hunger-facts-international.html • 963 million people across the world are hungry. • Every day, almost 16,000 children die from hunger-related causes--one child every five seconds. 

39. Thank you!Welcome questions!E-mail: b.choi@uci.edu