01/23/2014 08:51 am ET | Updated Jan 24, 2014

Truck Driving, Cleaning Services Top List Of Most Obese Jobs

The transportation, moving, cleaning, truck-driving, protective services and building services industries have the highest prevalence of obesity, according to a study of people in Washington state.

For instance, 38.6 percent of truck drivers in the study were obese, compared with 11.6 percent of people in the medical fields (such as doctors, veterinarians and dentists). Protective services workers and truck drivers had the highest obesity risks of all industries in the study, when using people in health fields as a baseline to determine risk. (However, this finding could be explained by the fact that people working in protective services fields, like firefighters, may be more muscular, thereby skewing their body mass index upward.)

"BMI measures cannot distinguish between fat and lean tissue mass; workers with physically demanding jobs may be more physically fit and have a higher BMI because of increased muscle mass," the researchers wrote in the study. "For example, protective services (e.g., firefighters, police officers) had a high prevalence of obesity but also had the highest proportion of vigorous LTPA [leisure time physical activity]."

Indeed, people working in protective services were most likely to report getting vigorous exercise -- 50.8 percent -- followed by people working in health-related fields and postsecondary teachers. Meanwhile, machine workers -- operators, inspectors and assemblers -- were least likely to report getting vigorous exercise.

The findings, published in the Centers for Disease Control and Prevention journal Preventing Chronic Disease, are based on data from 37,626 people in Washington state who reported an occupation when the survey was conducted. The overall prevalence of obesity among the workers was 24.6 percent.

Here is the ranking of obesity prevalence, from most to least, based on occupational group:

1. Truck drivers - 38.6 percent
2. Transportation and material moving - 37.9 percent
3. Protective services - 33.3 percent
4. Cleaning and building services - 29.5 percent
5. Health services - 28.8 percent
6. Mechanics and repairers - 28.9 pecent
7. Administrative support - 27.9 percent
8. Personal services - 27.2 percent
9. Technicians (plus related support) - 26.6 percent
10. Precision production and plant operators - 26.1 percent
11. Sales 25.4 percent
12. Management-related - 25.1 percent
13. Executive, administrative and managerial - 24.4 percent
14. Machine operators, assemblers and inspectors - 23.9 percent
15. Registered nurses - 22.6 percent
16. Farming, forestry and fishing - 22.3 percent
17. Teachers (not including postsecondary education) - 21.8 percent
18. Helpers, equipment cleaners and laborers - 21.9 percent
19. Math and computer scientists - 21.8 percent
20. Lawyers and judges - 21.7 percent
21. Engineers, architects and surveyors - 20.2 percent
22. Food preparation and service - 20.1 percent
23. Construction - 19.9 percent
24. Other professional specialties - 19.7 percent
25. Health assessment and treating (not including registered nurses) - 18.2 percent
26. Postsecondary teachers -17.6 percent
27. Natural and social scientists - 17.3 percent
28. Health-diagnosing occupations - 11.6 percent

The study also showed that truck drivers were most likely to be smokers and least likely to eat five or more daily servings of fruits and vegetables, while people working in health-related fields were least likely to be smokers and most likely to get their daily produce intake.

Researchers noted that the findings are similar to a more nationally representative study, conducted between 1986 and 2002, also showing that "motor vehicle operators, workers in other transportations, workers in cleaning and building services, material-moving equipment operators, and workers in protective services had the highest obesity prevalence."

They pointed out that occupation is often linked to other characteristics -- such as race and ethnicity, sex, age, education and socioeconomic status -- which could explain the differences in exercise, obesity and fruit and vegetable consumption. In addition, they noted that the study only showed an association, and does not prove that working in a certain field causes obesity.