Table 4.

Isotemporal Substitution of Activities, per 30-Minute/Day Increase and 6-Year Weight Change (Kilograms), for US Premenopausal Women From 1991 to 1997

Analysis Method	TV Watching		Slow Walking		Brisk Walking		Jogging/Running		Other Activities		Total Activitya
	β0b	95% CI	β1b	95% CI	β2b	95% CI	β3b	95% CI	β4b	95% CI	β5b	95% CI
Substitution of activity to replace TV watching
Substitution model A	Dropped		−1.02	−1.55, −0.48	−2.16	−2.64, −1.68	−3.73	−4.89, −2.57	−1.73	−2.13, −1.33	0.47	0.36, 0.59
Substitution of activity to replace slow walking
Substitution model B	1.02	0.48, 1.55	Dropped		−1.14		−1.75, −0.53	−2.71	−3.97, −1.45	−0.72	−1.39, −0.04	−0.54	−1.07, −0.02
Substitution of activity to replace brisk walking
Substitution model C	2.16	1.68, 2.64	1.14	0.53, 1.75	Dropped	−1.57	−2.82, −0.33	0.43	−0.22, 1.07	−1.69	−2.15, −1.22
Substitution of activity to replace jogging/running
Substitution model D	3.73	2.60, 4.89	2.71	1.45, 3.97	1.57	0.33, 2.82	Dropped		2.00	0.77, 3.22	−3.26	−4.41, −2.10
Substitution of activity to replace other activities
Substitution model E	1.73	1.33, 2.13	0.72	0.04, 1.39	−0.43		−1.07, 0.22	−2.00	−3.2, −0.77	Dropped		−1.26	−1.65, −0.87
Comparison of results vs. those from other nonisotemporal substitution models
Partition modelc F	0.47	0.36, 0.59	−0.54	−1.07, −0.02	−1.69	−2.15, −1.22	−3.26	−4.41, −2.10	−1.26	−1.65, −0.87	N/A
Single activity modelsd	0.48	0.37, 0.60	−0.11	−0.62, 0.41		−1.66	−2.11, −1.21	−3.44	−4.62, −2.26	−1.49	−1.88, −1.10	0.16	0.05, 0.27
	(model G)		(model H)		(model I)		(model J)		(model K)		(model L)

Abbreviations: CI, confidence interval; N/A, not applicable.

^a Total activity includes total discretionary physical activity and TV watching.

^b All models were adjusted for baseline (1991) age (years), weight (kilograms), and height (meters); total average alcohol intake (1991, 1995) (0, >0–<2.5, 2.5–5, >5–10, >10 g/day); sugar-sweetened beverage intake (1991, 1995) (0, >0–0.5, >0.5–1, >1 serving/day); energy-adjusted trans-fat intake (1991, 1995) (≤2.5, >2.5–3, >3–4, >4 g/day); energy-adjusted fiber intake (1991–1995) (5–15, >15–20, >20–25, >25 g/day); oral contraceptive use (1997) (never, current, past); smoking (1989, 1997) (never; past: >0–7 pack-years, past: ≥8 pack-years; current: >0–19 pack-years, current: ≥20 pack-years); parity (1997) (never given birth, 1 birth, 2 births, ≥3 births); and antidepressant use (1997) (never, current, past).

^c Total activity is partitioned among TV watching, slow walking, brisk walking, jogging/running, and other activities (biking, swimming, lawn mowing, aerobics, tennis, and stair climbing). Each regression coefficient (and 95% CI) represents a comparison of weight regain (in kilograms) for every 30-minute/day increase in the predictor variable, not restricting total physical activity time nor controlling the displacement of other activity time.

^d Each component of total activity is entered separately in a single model.