This study used objective data obtained from accelerometers to compare bariatric surgery candidates and normal-weight controls on total PA and PA performed at different intensities in bouts of varying duration. Bariatric surgery candidates performed less PA overall and spent fewer minutes per day in MVPA and VPA compared to controls. More than two-thirds (68%) of bariatric surgery candidates had no MVPA in bouts ≥ 10 min compared to only 13% of controls. Furthermore, only 4.5% of bariatric surgery candidates met national PA guidelines to accumulate ≥ 150 min/wk of MVPA in bouts ≥ 10 min [14
], compared to 40% of controls. Taken together, these findings suggest that when compared to normal-weight individuals, most bariatric surgery candidates move less throughout the day and are less likely to participate in PA of a sufficient intensity and duration to improve and maintain health and manage body weight [14
Our findings are similar to those from recent studies suggesting low levels of PA in bariatric surgery patients preoperatively. In a study of 190 RYGB patients, nearly two-thirds (64%) were inactive, defined as self-reported accumulation of < 200 min/wk of MVPA including walking in ≥ 10 min bouts [4
]. King and colleagues [13
] showed a variety of PA levels among 757 bariatric surgery candidates from the LABS study, although most (80%) were either inactive or insufficiently active based on objective step counts (i.e. <10,000 steps/day). Consistent with the findings of King et al., bariatric surgery candidates in the present study exhibited a wide range of PA levels, although most were inactive or insufficiently active based on accelerometer activity counts/hour and time (min/wk) accumulated in MVPA bouts ≥ 10 min. Indeed, 91% of the bariatric surgery candidates recorded fewer than 18,972 accelerometer activity counts/hour, a cut-off roughly equivalent to 10,000 steps/day , and 95% failed to meet the national recommendation to accumulate 150 weekly minutes of MVPA in ≥ 10 min bouts [14
Similar to previous studies that have compared PA levels in obese and non-obese individuals using accelerometers [20-23], we found that severely obese individuals preparing to undergo bariatric surgery engage in less PA of at least a moderate intensity than their normal-weight counterparts. Bariatric surgery candidates spent 50% less time each day in MVPA, compared to controls (26 vs 52 min/day). In addition, more than two-thirds (68%) of bariatric surgery candidates did not accumulate any MVPA in bouts ≥ 10 min versus 13% of controls. These findings are consistent with those from a recent population-based study showing that higher BMI and larger waist circumference are associated with lower levels of accelerometer-determined MVPA occurring in bouts ≥ 10 min [23
Finally, the finding that only 1 of the 22 bariatric surgery candidates in this study met the recommended 150 minutes of MVPA in bouts ≥ 10 min is striking. Moreover, the majority of bariatric surgery candidates were not even close to meeting these criteria—15 (68%) had no MVPA bouts ≥ 10 min and 21 (95%) accumulated less than 50 min/wk of MVPA in ≥ 10 min bouts. These findings support previous research showing lower objective adherence to recommended PA levels in non-severely obese versus normal-weight individuals [20
] and strongly suggest that meeting existing PA guidelines geared towards the general population may be too challenging from a physical and/or motivational standpoint for many bariatric surgery patients preoperatively. Consequently, interventions to increase PA in bariatric surgery candidates may be most effective when a variety of strategies are employed, such as: shaping PA behavior through goals that promote gradual increases in PA amount and intensity [24
]; encouraging accumulation of daily PA in multiple short bouts versus a long single bout [25
]; prescribing slower walking on a flat surface to minimize adverse biomechanical effects of severe obesity [26
]; reducing sedentary behaviors to increase number of opportunities for lifestyle and structured PA [27
]; and teaching other techniques such as self-reinforcement and stimulus control to increase low PA motivation and commitment [24
This study is the first to: 1) use the RT3 accelerometer, a device used in large scale observational and treatment studies [10
], in a bariatric surgery patient population; 2) objectively determine time spent by bariatric surgery candidates performing PA at different levels of intensity and in MVPA bouts ≥ 10 minutes, relative to normal weight controls; and 3) compare these groups on objective adherence to national physical activity recommendations. These strengths and novel aspects advance previous PA research involving bariatric surgery patients, which has largely relied on self-report measures to assess PA and not directly compared PA in this group with that of normal-weight individuals.
A number of study limitations should also be considered. Although accelerometers are able to overcome certain limitations of questionnaires such as over-reporting, types of exercise and non-exercise related activities performed cannot be determined. Additional studies are needed to evaluate the extent to which the RT3 provides a valid assessment of different structured activities (e.g., walking, cycling, etc.) performed by bariatric surgery patients. Accuracy of the RT3 in detecting vertical movement may have been limited in bariatric surgery candidates as a result of monitor tilting due to excess adiposity and abnormal walking or gait abnormalities [8
]. Further research is required to understand how these and other physical limitations affect performance and measurement of lifestyle and structured activities. The activity count thresholds that were used to define MVPA and VPA are based on a younger and leaner sample [16
], which may affect the accuracy of these classifications in our sample. Bariatric surgery candidates in this study were ambulatory and controls were homogeneous to race which may limit generalizability of our findings to the respective populations. Overall, the sample was relatively small and self-selected. It is possible that participants, particularly controls, were more physically active than individuals who were unmotivated to participate. We did not collect specific information concerning occupation or socioeconomic status (SES) level, although analyses adjusting for education level (a common proxy of SES) did not change our pattern of findings. Nonetheless, additional studies are needed to examine whether occupation, length of work day and related sitting time contribute to differences in PA between bariatric surgery patients and normal-weight individuals on work and non-work days. Finally, less than two-thirds (64%; 48% of surgery candidates and 75% of controls) of participants who wore an accelerometer from which data could be retrieved met the wear requirement on ≥ 4 days, although analyses including all participants with at least 1 day of valid wear did not alter the pattern of findings. Future research is needed to determine an appropriate balance between accelerometer wear time and participant burden, particularly among bariatric surgery patients.
In summary, the present study is the first to use accelerometers to compare PA in bariatric surgery candidates and normal-weight controls. Compared to controls, bariatric surgery candidates moved less throughout the day and spent less time in PA of at least a moderate intensity. Moreover, less than 5% of bariatric surgery candidates met the national PA recommendation to accumulate 150 weekly minutes of MVPA in bouts lasting at least 10 minutes, compared to 40% of controls. Future research is needed to determine how best to increase PA in bariatric surgery candidates and the effects of accelerometer-determined PA patterns and intensity on postoperative weight and health-related outcomes.