Measurement of Weight in Clinical Trials: Is One Day Enough?
Table 1
Mean weight change (standard deviation) and weight variability among control participants in weight loss
All
African
Non-African
american
N
316
134
158
113
203
113
203
Baseline characteristics
Mean age (SD), years
55.8 (8.5)
57.3 (8.2)
54.9 (8.4)
56.6 (8.6)
55.4 (8.5)
53.5 (9.0)
57.1 (8.0)
% Female
64.2
61.9
67.1
0
100
71.7
60.1
% African American
35.8
26.9
44.9
28.3
39.9
100
0
% Overweight
42.4
100
0
45.1
40.9
31.9
48.3
% Obese
50
0
100
46
52.2
62.8
42.9
Mean BMI (SD), kg/m2
30.8 (4.5)
27.7 (1.4)
34.5 (3.2)
30.3 (4.1)
31.2 (4.7)
32.1 (4.9)
30.1 (4.1)
Mean weight, kg
86.9 (15.0)
78.4 (8.8)
96.6 (13.4)
94.7 (15.1)
82.5 (13.1)
89.5 (15.9)
85.4 (14.3)
N for 12-month analysis
309
131
155
109
200
110
199
12-Month weight Δ (SD), kg
Single day
3.9 (5.1)
3.5 (4.3)
4.5 (5.7)
3.9 (5.8)
3.9 (4.6)
3.6 (4.4)
4.0 (5.4)
Two days
3.9 (5.0)
3.5 (4.2)
4.5 (5.7)
3.9 (5.8)
3.9 (4.5)
3.6 (4.4)
4.1 (5.3)
N for 30-month analysis
281
116
141
104
177
101
180
30-Month weight Δ (SD), kg
Single day
6.0 (6.3)
5.7 (5.1)
6.4 (7.4)
6.7 (8.0)
5.5 (5.0)
5.4 (5.0)
6.2 (6.9)
Two days
6.0 (6.3)
5.8 (5.0)
6.4 (7.4)
6.6 (8.1)
5.6 (4.9)
5.4 (5.0)
6.3 (6.9)
% Total variance
Between-individual, %
91.3
82.4
86.7
88.9
90.7
93.5
89.9
Between-visit, %
8.5
17.1
13
10.9
9
6.3
9.9
Within-visit, %
0.2
0.4
0.3
0.2
0.2
0.2
0.2
SD: standard deviation; kg: kilograms; BMI: body mass index P values .70 for all F-tests comparing standard deviations within each group (e.g., for all participants, comparing SD of mean weight change at 30 months using a single day (6.3 kg) to that using 2 days (6.3 kg), ). BMI 25–29.9 kg/m2 BMI30 kg/m2 BMI 25 kg/