Changes in working hours and the associated time and energy consumed during work can exert an important influence on people’s fitness. However, the effects of such changes on health behaviour and obesity are not well understood. This column examines the effects of a 2001 French national reform that reduced working hours on employee obesity and overweight. Although reduced working times could, in theory, be used for health-promoting activities, in practice it had different effects on white- and blue-collar workers. Policies to reduce working hours alone do not necessarily produce better fitness for everyone.

The expansion of the world’s obese and overweight population is associated with energy-saving social and economic changes (Cutler et al. 2003). Rapid social globalisation (changes in transport times, culture, and communication, for example), rather than economic interdependence, has been associated with changes in health-related behaviours, which have an impact on health outcomes and on an individual’s fitness. This has been coined ‘globesity’ by some (Costa-Font and Mas 2016). 

One such social change refers to employment conditions and, specifically, working hours. Time and energy consumed during work hours can exert an important influence on people’s fitness. Many organisations, including the OECD (1998), identify an overall downward trend in working time. Nonetheless, the effects of working times on health behaviour, and specifically obesity and overweight, are not well understood. 

The most common explanations of the effect of long working hours on overweight focus on the stress response and poor lifestyles of working extra hours. However, other effects can come through changes in sedentary lifestyles among white-collar workers or non-sedentary lifestyles among blue-collar workers, and especially changes in time constraints that modify the opportunity cost of investing in healthy lifestyles (cooking fresh food, exercising, etc.). 

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Working time and health in theory and evidence

From a demand-for-health standpoint (Grossman 1972), economic principles suggest that longer working hours constrain the amount of time individuals spend on healthy activities such as food preparation and seeking preventive health care. Employees compensate excessive working time with higher consumption of fat and sugars and reductions on physical exercise (Oliver and Wardle 1999). 

On the other hand, increased working hours could have income effects, namely, the raising of labour income, which can then be invested in health production. However, income effects might differ between white- and blue-collar workers. For the latter, exercise through working might be an important source of physical exercise; hence a reduction in working times might not produce positive health-investment effects.

The evidence on the effects of working time on health is mixed. Ruhm (2005) finds that a reduction in the number of hours worked has a positive impact on health among the US population. Similarly, based on time-use surveys, Hammermesh (2010) finds that the amount of time spent eating and its distribution over the day influence bodyweight and self-reported health. Hence, relaxing time constraints should produce better health and allow individuals to adjust to life demands that require more exercise and lower calorie consumption. However, causal testing of such a hypothesis requires an exogenous variation in working times among a control group. 

Furthermore, working-time reduction does not necessarily entail homogeneous effects across the entire population. Blue-collar workers might benefit from shorter working days, but at the same time, they might see one source of fitness reduced. In contrast, white-collar workers might benefit from more free time, especially if such extra time is devoted to health-related activities – although white-collar jobs tend to encompass more employment flexibility.

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Evidence from the Aubry reform

One source of evidence of the effects of working time on health comes from working-time reforms. The Aubry reform, implemented in France at the beginning of the last decade, reduced the workweek from 39 to 35 hours, or by 184 hours per year. Askenazy (2013) estimates that this reform resulted in an overall 7% reduction of working time from 1995 to 2003, compared to 3% elsewhere in the EU.

In our study (Costa-Font and Saenz de Miera 2018), we use a difference-in-differences strategy to study the causal effect of a change in working time on overweight and obesity, drawing on evidence from the Aubry reform and focusing on one region, Alsace-Moselle, which the impact of the national policy by counting two existing public holidays. We use longitudinal data from GAZEL (INSERM) 1997-2006, which follows employees of EDF-GDF, a major electricity and gas provider that implemented the 35-hour workweek one year earlier than the rest of the country (in 2000). Furthermore, we exploit a heterogeneous effect between blue- and white-collar workers. 


We find that blue-collar workers in treated areas (where the 35-hour reform was fully enforced) exhibit a 6.7 percentage point higher probability of being overweight than their counterparts in control areas (Alsace-Moselle). The reduction in working time was employed in reducing the use of external childcare rather than increasing leisure time. Consistently, overweight declined if the spouse was employed. A reduction in working time was reflected in a small deterioration in the intensive margin of self-reported health. These results are consistent with other evidence on the French reform (Goux et al. 2014).

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Policy implications

The evidence overall suggest that policies to reduce working times alone do not necessarily result in better fitness for everyone, either because they do not modify the environment (e.g. individuals take more holidays) or because they produce counterproductive incentives in a population for whom job-related physical activity is the primary form of exercise (i.e. blue-collar workers). 

In contrast, for certain subsets of the population, we do find some health effects such as those individuals who are obese at the baseline. One potential policy solution would be to combine working-time reduction with incentives to use the extra leisure time on health-production activities.


Askenazy, P (2013), “Working time regulation in France from 1996 to 2012”, Cambridge Journal of Economics 37: 323–347.

Costa-Font, J, and N Mas (2016), “‘Globesity’? The effects of globalization on obesity and caloric intake”, Food Policy 64: 121-132.

Costa-Font, J, and B Sáenz de Miera Juárez (2018), “Working times and overweight: Tight schedules, weaker fitness?”, CESifo Working Paper No. 7174, Center for Economic Studies and Ifo Institute (CESifo), Munich.

Cutler, D M, E L Glaeser and J M Shapiro (2003), “Why have Americans become more obese?”, The Journal of Economic Perspectives 17(3): 93–118.

Hamermesh, D (2010), “Incentives, time use and BMI: The roles of eating, grazing and goods”, Economics and Human Biology 8: 2–15.

Oliver, G, and J Wardle (1999), “Perceived effect of stress on food choice”, Physiology and Behavior 66: 511–515. 

Ruhm, C (2005), “Healthy living in hard times”, Journal of Health Economics 24(2): 341–363.