Development and validation of a food photography manual, as a tool for estimation of food portion size in epidemiological dietary surveys in Tunisia

Figures & data

Fig. 1 Example of photographs from the photos manual shows portion sizes of food and the amounts in grams. (a) Couscous, (b) fish, (c) fresh vegetables, (d) apples.

Fig. 2 Bland–Altman plots for estimated and weighed food amounts. (a) Meat, (b) vegetables, (c) fruits.

Table 1 Amount of food estimated by FP 24-hR and compared with amount weighed in FW

		FP 24-hR		FW
Food categories (g)	n	Mean	SD	Mean	SD	Spearman (r)	Difference^a (%)	CI (95%)	Limit of agreement
Bread	25	146.7	82.1	140.3	70.2	0.892**	4.6	−7.5 to 20.5	−60.2 to 73.1
Pasta	19	207.8	88.3	175.2	63.0	0.859***	18.6*	10.9 to 54.2	−55.5 to 120.7
Potatoes	7	76.9	21.5	75.1	37.0	0.926**	2.3	−17.4 to 20.9	−38.8 to 42.3
Animal products	30	98.2	51.1	109.0	70.2	0.937**	−9.9	−22.2 to 0.62	−70.7 to 49.1
Vegetables	28	97.0	65.1	92.4	68.3	0.931**	4.1	−7.1 to 16.2	−54.5 to 63.7
Fruits	21	129.5	115.9	124.7	88.2	0.986***	3.7	−16.8 to 26.2	−88.1 to 97.5
Dairy products	29	249.5	82.8	244.0	85.3	0.978***	2.2*	0.7 to 10.3	−19.2 to 30.4
Sweet products	26	186.5	176.2	195.3	184.1	0.968**	−4.5	−26.5 to 8.8	−94.8 to 77.1

SD: standard deviation. *p<0.05, *p<0.01, ***p<0.001.

^aPercent of the mean difference=[(amount from FP 24-hR−amount from FW)/(mean amount from FW)*100].

Fig. 3 Bland–Altman plots for estimated and weighed food amount. (a) Protein, (b) fat, (c) carbohydrate.

Table 2 Mean nutrient intake and comparison of the results obtained with the FP 24-hR and FW methods

	FP 24-hR		FW
Nutrients	Mean	SD	Mean	SD	Pearson (r)	Difference^a (%)	CI (95%)	Limits of agreement
Energy (Kcal)	1,949	510.0	1,940	454	0.943**	0.46	−53.2 to 72.4	−326.1 to 345.3
Protein (g)	64.56	18.32	64.28	18.82	0.889**	0.43	−2.9 to 3.4	−16.8 to 17.4
Fat (g)	66.81	22.94	73.20	24.42	0.920**	−8.21**	−9.9 to 2.8	−25.1 to 12.4
Carbohydrate (g)	272.72	91.67	256.12	74.12	0.934**	6.47	3.8 to 29.3	−51.5 to 84.6
Dietary fiber (g)	17.12	8.49	15.71	7.17	0.926**	8.90*	0.2 to 2.6	−5.0 to 7.8
Vitamin B1 (mg)	1.19	1.40	1.23	1.37	0.985**	−2.40	−0.1 to 0.05	−0.5 to 0.4
Vitamin C (mg)	50.29	50.91	48.51	47.89	0.927**	3.60	−5.2 to 8.7	−35.7 to 39.3
Vitamin E (mg)	6.02	3.14	6.82	3.39	0.935**	−11.60	−1.2 to 0.3	−3.14 to 1.5
Calcium (mg)	467.25	152.93	458.93	149.13	0.644**	1.81	−9.0 to 25.7	−84.6 to 101.3
Folate (µg)	184.77	97.38	176.65	109.08	0.951**	4.59	−24.0 to 40.3	−163.9 to 180.1
Iron (mg)	8.61	3.12	8.60	2.75	0.755**	0.003	0.2 to 2.6	−4.0 to 4.0
Zinc (mg)	3.53	1.20	3.98	1.86	0.747**	−11.05	−0.9 to 0.01	−2.9 to 2.0

SD: standard deviation. *p<0.05, **p<0.001.

^aPercent of the mean difference=[(amount from FP 24-hR−amount from FW)/(mean amount from FW)]*100.