Table 1 Differences between mean self-reported (SR) and measured BMI values (SR BMI – measured BMI). Paired t-tests (2-tailed) assessing differences between self-report (SR) and measured BMI values are presented by sex and country for older (50+ years old) and younger (18–49 years old) individuals, with degrees of freedom (df)

China

23.5-23.6 = −0.1

24.17-24.22 = −0.6

23.5-23.2 = 0.2

23.1-23.4 = −0.3

t(5623) = −1.03

t(6439) = −0.808

t(678) = 1.435

t(869) = −2.400*

India

23.8-20.7 = 3.1

27.0-21.3 = 5.7

22.7-20.6 = 2.1

24.1-20.7 = 3.4

t(1528) = 8.711***

t(964) = 8.815***

t(575) = 5.196***

t(1325) = 7.534***

Mexico

28.0-28.3 = −0.3

28.8-29.3 = −0.5

28.3-28.7 = −0.4

28.4-29.0 = −0.6

t(286) = −0.837

t(308) = −2.740**

t(48) = −1.664

t(79) = −1.935

Russia

27.0-27.3 = −0.3

29.2-29.7 = −0.4

25.4-26.3 = −0.9

26.0-26.4 = −0.4

t(1235) = −3.540***

t(2202) = −6.888***

t(143) = −0.914

t(234) = −2.252*

South Africa

31.2-29.2 = 2.0

33.4-32.6 = 0.8

30.1-29.1 = 0.9

31.2-29.9 = 1.4

t(406) = 3.016**

t(508) = 1.310

t(36) = 0.534

t(51) = 0.762