Overweight and obesity are classifications of a person’s excess body fat and are commonly assessed using the Body Mass Index (BMI). The BMI is derived from a person’s weight (in kilograms) divided by their height (in meters) squared (kg/m²). An adult is considered overweight if their BMI is greater than 25 kg/m²

and obese if their BMI is greater than 30 kg/m² (Table 1). Further research is required to determine if the use of a high BMI is indicative of health risk, in that very muscular people can register a high BMI, due to heavy muscle mass rather than excess body fat. Other methods such as calculating the waistto-hip ratio with a measuring tape, or using callipers to measure excess body fat may be more indicative of poor health outcomes.

Implications of overweight and obesity for the workplace

The increasing rate of obesity in the community will have implications for workplaces and employers. Research shows that overweight people are more likely to have additional health risks, short-term disability, longer absence due to illness and higher health costs compared to those with a lower BMI (Burton et al. 1998). This means that overweight workers may be less productive, more prone to injury and have higher claim costs. If strategies are not developed to address rising obesity, there could be significant consequences for both employers and employees.

Increased workplace absenteeism, lower productivity and work limitations

Studies indicate that excess weight and physical inactivity are associated with employees’ work performance. Obese workers are more likely to take sick leave and be less productive (Narbro et al. 1996). Further, according to the same survey findings, obese employees were 17% more likely than non-obese employees to be absent from work for at least one day during the previous two weeks because of personal injury or illness.

Increased injury and illness incidence

Larger workers and physically unfit individuals may be more prone to accidents and nonfatal injuries. Obesity restricts physical functioning including mobility and flexibility, consequently this may lead to a higher risk of injury compared to persons without such limitations. In a study that collected data over a one-year period from a total of 370 respondents who reported injuries in the previous year, Xiang et al (2005) observed a linear dose-response trend among women. An estimated 7.0% of underweight individuals (with BMI less than 18.5) reported injuries. In contrast, 26.0% of men and 21.7% of women with a BMI greater than 35.0 reported injuries . A range of studies have shown that BMI, or fat mass, is positively related to disability. Obese and overweight persons can find it difficult to perform some work duties, especially physically intensive tasks.

Increased musculoskeletal disorders

Obesity may be a factor in increasing the likelihood of workplace musculoskeletal injuries. For example, there is a risk of musculoskeletal disorders if there is mismatch between a person’s physical needs, abilities and limitations and the working environment, plant and equipment and required tasks. Ergonomic assessment of these potential mismatches will be required to ensure the design and evaluation of tasks, jobs, plant, environments and systems are compatible with the needs, abilities and limitations of people.

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The International Classification of adult underweight, overweight and obesity according to BMI



Principal cut-off points

Additional cut-off points




Severe thinness



Moderate thinness

16.00 - 16.99

16.00 - 16.99

Mild thinness

17.00 - 18.49

17.00 - 18.49

Normal range

18.50 - 24.99

18.50 - 22.99

23.00 - 24.99





25.00 - 29.99

25.00 - 27.49

27.50 - 29.99




Obese class I

30.00 - 34-99

30.00 - 32.49

32.50 - 34.99

Obese class II

35.00 - 39.99

35.00 - 37.49

37.50 - 39.99

Obese class III



Source: Adapted from WHO, 1995, WHO, 2000 and WHO 2004.