Table 3.

Mean and SD of weight difference (measured - self-reported weight in kilograms) by survey year, BMI categories, and socio-demographic characteristics ^a

Characteristic	N	Survey year					Test for trends b
		1999–2000	2001–2002	2003–2004	2005–2006	2007–2008	p value
Overall	18,394	0.76	0.65	0.44	0.70	0.70	0.855
		(4.215)	(4.445)	(4.010)	(4.619)	(4.236)	0.724
Sex
Male	9,373	−0.15	−0.28	−0.28	0.06	−0.15	0.358
		(3.671)	(4.500)	(3.923)	(4.959)	(4.085)	0.134
Female	9,021	1.66	1.57	1.14	1.33	1.52	0.228
		(4.515)	(4.191)	(3.971)	(4.165)	(4.220)	0.529
Race/ethnicity
Non-Hispanic White	10,000	0.83	0.69	0.45	0.71	0.75	0.710
		(3.819)	(4.239)	(3.640)	(4.408)	(3.959)	0.593
Non-Hispanic Black	4,312	0.58	0.44	0.53	0.74	0.65	0.537
		(6.057)	(5.359)	(5.727)	(5.841)	(5.558)	0.692
Mexican American	4,082	0.19	0.53	0.15	0.50	0.28	0.871
		(4.710)	(4.962)	(4.322)	(4.518)	(4.384)	0.309
Age
20–39	6,232	0.82	0.68	0.42	0.49	0.66	0.287
		(4.464)	(4.911)	(4.150)	(4.846)	(4.428)	0.870
40–59	6,218	0.77	0.67	0.57	1.01	0.76	0.427
		(4.160)	(4.415)	(4.249)	(4.914)	(4.361)	0.413
60–89	5,944	0.61	0.52	0.22	0.44	0.63	0.913
		(3.785)	(3.396)	(3.176)	(3.408)	(3.527)	0.584
BMI categories
BMI < 30	12,110	0.08	−0.04	−0.26	−0.13	−0.10	0.135
		(3.153)	(3.226)	(3.041)	(3.343)	(3.179)	0.584
BMI >= 30	6,284	2.32	2.18	1.90	2.27	2.24	0.953
		(5.704)	(6.108)	(5.216)	(6.073)	(5.432)	0.678

^aStandard deviations (SD) are presented in parentheses. Observations are weighted to be nationally representative of the U.S. population.

^bTest results of trends in weight difference (measured - self-reported weight) are based on simple liner regression models regressing weight difference on survey year. Test results of trends in the standard deviation are based on simple linear regression models regressing squared residuals on survey year.