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Can J Public Health. 2019 Jan 4. doi: 10.17269/s41997-018-0165-z. [Epub ahead of print]

Influence of physical activity, screen time and sleep on inmates' body weight during incarceration in Canadian federal penitentiaries: a retrospective cohort study.

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Interdisciplinary School of Health Sciences, University of Ottawa, 25 University Private, Ottawa, Ontario, K1N 7K4, Canada.
Healthy Active Living and Obesity Research Group, Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada.
School of Epidemiology and Public Health, University of Ottawa, Ottawa, Ontario, Canada.



Recent research found that inmates experience undesirable and rapid weight gain during incarceration in Canadian federal penitentiaries. However, little is known about what factors and daily movement behaviours (e.g., physical activity, screen time, and sleep) influence weight gain during incarceration. This study examines how these 24-h movement/non-movement behaviours contribute to weight gain during incarceration.


This retrospective cohort study explored how weight change outcomes during incarceration (weight change, body mass index (BMI) change, and yearly weight gain) were influenced by physical activity, screen time, and sleep in a convenience sample of 754 inmates. The outcome measures were taken twice, once from participants' medical chart at admission and again during a face-to-face follow-up interview (conducted in 2016-2017; mean follow-up time of 5.0 ± 8.3 years). Physical activity, screen time, and sleep were self-reported. The statistical analysis was chi-square testing, non-parametric median comparison testing, and regression analysis to control for confounders.


Inmates who engaged in at least 60 min of daily physical activities gained less weight (4.5 kg) compared to inmates who reported not exercising (8.3 kg). Different types of exercise (cardiovascular exercises, weight lifting, and team sports) were helpful at limiting weight gain, but playing sports was the most effective. Screen time and sleep were not associated with weight gain outcomes.


Among the behaviours examined, physical inactivity was significantly associated with higher weight gain during incarceration. However, even high levels of physical activity (> 60 min/day) were not sufficient to eliminate weight gain during incarceration in Canada.


BMI; Inmates; Obesity; Penitentiary; Physical activity; Sedentary behaviours


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