Background/Purpose: Moderate-to-vigorous physical activity
(MVPA) is recommended for weight loss; however it is unclear how activity or
sedentary changes influence long-term weight loss in obese adults. We examine
if changes in MVPA, light intensity physical activity, and sedentary behavior
are related to weight loss over a 2 year period in obese adults with knee osteoarthritis
(OA) or knee OA risk factors.

Methods: Objectively measured body weight,
physical activity, and sedentary time were obtained from 459 obese participants
from the Osteoarthritis Initiative at baseline and two years. Weight change was
categorized as ≥10, 5.0-9.9, 4.9 to -4.9, -5.0 to-9.9, ≤-10 lbs. The
association between 2-year weight change and changes in physical activity
(light and MVPA) and sedentary time from accelerometer monitoring were examined
by multiple linear regression adjusted for baseline weight, demographic and
health factors.

Results: Over 2 years, participants lost 3.48 ±
26.06 lbs., increased sedentary time (9.5 ± 64.5 minutes) and decreased both
light and MVPA (-8.6 ± 64.5 minutes, -0.9 ± 14.2 minutes, respectively). Weight
loss was associated with increased MVPA gains across five categories of weight
change from ≥10lbs. loss (5.2 min), 5-9.9lbs. loss (2.4 min), ±5lbs. (1.4
min), 5-9.9lbs. gain (-0.9 min), and ≥10lbs. gain (-2.7 min) (p for trend
< 0.001).  Weight loss was also associated with less sedentary gain across
five categories of weight change from ≥10lbs. loss (-7.1 min), 5-9.9lbs.
loss (7.3 min), ±5lbs. (9.1 min), 5-9.9lbs. gain (9.5 min), and ≥10lbs.
gain (25.8 min) (p for trend =0.01). Weight loss had a strong but
nonsignificant trend with light activity gain (p for trend = 0.06). All models
controlled for baseline weight, demographics and health factors.

Conclusion: Decreases in sedentary time over 2
years and small increases in MVPA and were associated with weight loss among
obese adults with or at risk for knee osteoarthritis.