Comparison of multiple and novel measures of dietary glycemic carbohydrate with insulin resistant status in older women

Table 2 Comparison of nine dietary glycemic intake variables and their relative contribution to prediction of insulin resistant status in LAW study subjects (n = 200)

Glycemic variable	Mean glycemic intake^†		Odds of insulin resistance^§	Nagelkerke's R² coefficient^¶
	Subjects with insulin resistance (n = 19)	Subjects with-out insulin resistance (n = 181)	Odds ratio (95%CI)	R ² value with variable	Increase in R ² value	P value
None (baseline)				0.529	n/a	n/a
Daily glycemic measures:
GL per megacalorie	68.1 ± 9.1	58.2 ± 9.1**	1.21 (1.09-1.36)**	0.674	0.145	<0.01
GL	141 ± 33	117 ± 23**	1.10 (1.04-1.16)**	0.671	0.142	<0.01
Carbohydrate percentage	52.6 ± 5.1	46.6 ± 6.5**	1.36 (1.13-1.63)**	0.670	0.141	<0.01
Carbohydrate (g)	265 ± 54	227 ± 43**	1.06 (1.03-1.10)**	0.668	0.139	<0.01
GI	56.8 ± 3.4	55.9 ± 4.8	1.09 (0.91-1.29)	0.536	0.007	0.35
Meal glycemic measures:
GL peak score	38.9 ± 20.0	32.4 ± 10.8	1.06 (1.00-1.12)*	0.568	0.039	0.04
Lunch GL	33.4 ± 13.3	27.2 ± 9.5*	1.07 (1.00-1.14)*	0.566	0.037	0.04
Dinner GL	48.5 ± 25.1	41.8 ± 12.8	1.05 (0.99-1.10)	0.556	0.027	0.09
Breakfast GL	36.0 ± 12.7	30.5 ± 11.7	1.05 (0.99-1.13)	0.549	0.020	0.13

^†Independent t-tests used to compare subjects with and subjects without insulin resistance (defined as HOMA ≥ 3.99).
*P < 0.05, **P < 0.01.
^§ Logistic regression adjusted for age, age squared, waist circumference, body mass index, physical activity level, family history of diabetes, menopausal and hormone therapy status, saturated fat, alcohol, dietary fibre and energy.
^¶ Relative contributions to the predictive model of insulin resistant status, as measured by the increase in Nagelkerke's R² coefficient when individual glycemic variables were included in the logistic regression model with potential confounding factors. A larger increase in R² compared to baseline value indicates greater prediction of insulin resistance in the model.
HOMA: homeostasis model assessment for insulin resistance. Glycemic variables are defined in the Methods section. GL: glycemic load, GI: glycemic index.

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