Introduction

Obesity currently affects 20% of children in Spain, and the prevalence appears to be increasing dramatically.1,2,3 Epidemiologic data from the USA show that the prevalence of obesity in children is ∼25%.4

Obesity is the result of an energy imbalance in which energy intake exceeds energy expenditure. Although the caloric intakes of non-overweight and overweight children have been compared, few studies have compared the consumption in the course of the day and over a week. Although it is often assumed that overweight children eat more than non-overweight children do, no data have been published to support this belief. Some studies of energy intake among obese and non-obese children even suggest that obese children do not eat more than their non-obese peers.5

Because the eating habits may play an important role in the development or maintenance of obesity, we were interested in determining whether food consumption differed among the overweight and non-overweight. In addition, we examined the differences in dietary intake during the day and in the course of the week between overweight and non-overweight children.

Methods

Subjects

Participants were 32 children (16 males and 16 females) aged 11 y. This sample was randomly selected. All subjects were in good health. Students and parents were asked to read an explanation of the study and to sign an informed consent document.

Anthropometry

Height and weight of schoolchildren were measured; subjects wore lightweight clothing and no shoes. Height was measured to the nearest 0.1 cm using a stadiometer (Seca ref. 220) and weight to the nearest 0.1 kg using a beam-balance scale (Seca ref. 714). Data was compared with reference values for children;6 that was why the schoolchildren with weight-for-height >90th percentile were considered overweight.

Dietary intake

Some authors have noted that children routinely underestimate their intake on diet records5,7,8,9 and that obese children under-reported energy intake to a greater degree than lean children,10 although Davies et al11 found good agreement between weighed dietary records and energy expenditure in children whose records were kept by their parents. In the present study a dietician trained parents of children and they recorded dietary intake using the food weighing method12 (electronic scale, Soehnle, 2 kg max, 0–1000 g±1 g; 1000–2000 g±2 g) for 7 days.

Food diaries were analyzed for average nutrient content using the food composition tbl13 In addition to total energy and the energy distribution in the course of the day, average daily intake of the following dietary components were calculated: protein, carbohydrate, fat, saturated fat, monounsaturated and polyunsaturated fat, vitamins and minerals. Data were analyzed with comparison to the Recommended Dietary Allowances (RDA).14,15

Statistical analysis

Statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS/PC+, version 7.0). Data were analyzed using χ2 tests and Student's t-test. Statistical significance was set at P<0.01 and P<0.05.

Results

Some 46.9% of examined schoolchildren were considered overweight. Table 1 shows that more boys were considered overweight than girls (56.25% boys vs 37.5% girls). Both groups (non-overweight and overweight) reported energy intake in agreement with the recommendations,14 but the percentage energy intake reported in the overweight group was significantly lower than non-overweight (8948.7±2549.3 vs 9590.1±1884.9 kJ/day; P<0.01).

Table 1 Distribution of percentiles of weight for the heighta
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We compared reported macronutrient intake as a percentage of reported energy intake in the two groups (Table 2). Carbohydrate intake was significantly greater in the non-overweight schoolchildren (250.9±58.8 vs 222.1±77.4 g/ day; P<0.01). Fat and protein intake was not significantly different in both groups of children (fat intake, 114.6±32.7 g/day in non-overweight vs 109.7±38.4 g/day in overweight children; protein intake, 80.9±18.3 g/day in non-overweight vs 78.3±28.6 g/day in overweight children).

Table 2 Energy and macronutrient intake in non-overweight and overweight schoolchildren
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The mean daily intakes for fat consisted of 13.5% from saturated fat acids, 24.1% from monounsaturated fat acids, and 6.9% from polyunsaturated fatty acids. There were no significant differences in fatty acid intake among overweight and non-overweight schoolchildren. The mean cholesterol intake was 290.7±197.1 mg/day and the differences were not significant between both groups (283.9±189.1 in non-overweight vs 296.1±203.7 in the overweight group). The mean fiber intake was 13.16±8.2 g/day and was significantly greater in the non-overweight schoolchildren (14.8±9.1 g/day in non-overweight vs 11.8±7.1 g/day in overweight children; P<0.01).

Tables 3 and 4 show the descriptive statistics for the micronutrient intake. The vitamin A and D intakes were lower than recommendations.15 The mean daily intakes for calcium, magnesium and zinc were lower than recommendations.15 No significant differences between overweight and non-overweight children were found for micronutrient intake.

Table 3 Vitamin intake in non-overweight and overweight schoolchildren
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Table 4 Mineral intake in non-overweight and overweight schoolchildren
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The caloric distribution in the course of the day was: 17% breakfast, 3% mid-morning snack, 39% lunch, 15% afternoon snack and 26% dinner. The energy intake in the mid-morning snack and in the afternoon snack was significantly greater in the overweight schoolchildren than in the non-overweight group (mid-morning snack, 481.2±731.4 vs 253.1±599.1 kJ/day; P<0.01; afternoon snack, 1752.7±1112.1 vs 1401.2±1048.1 kJ/day; P<0.01).

Table 5 shows the differences between consumption during week and weekend days. The difference in protein intake between week and weekend days was significant in the total sample (81.6±25.5 g/day in the weekdays vs 73.9±21.4 g/day in the weekend days; P<0.05). No significant overweight vs non-overweight differences were found for dietary intake in the course of the week.

Table 5 Energy and macronutrient intake during the week and the weekend
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Discussion

The energy intake in both groups approximates the Recommended Dietary Allowances,14 but according to Bandini et al's data,16 the percentage energy intake reported was significantly lower in the overweight group. In the total sample, the energy intake was lower than reported by other authors.17,18 In contrast with our findings, Maffeis et al found no difference between energy intake in obese and non-obese children.19

The energy distribution in the course of the day agrees with the recommendations (15–25% breakfast, 25–35% lunch, 10–15% afternoon snack and 25–35% lunch). In addition, the energy intake in the mid-morning snack and in the afternoon snack was significantly greater in the overweight schoolchildren than in the non-overweight.

Reported protein intakes in both groups were similar and lower than RDA.15 Bandini et al16 found percentage energy from protein significantly lower in non-obese children compared to the obese children.

Furthermore, the total percentage of calories from fat was higher than the dietary guidelines20 recommended in both the overweight and non-overweight groups. In the total sample, lipid intake percentage was higher than those reported by other authors.17,18,19 Fat intake of overweight children was not statistically different from that of the non-overweight children. Other studies noted that the proportion of fat in the diet was greater in obese children.21 Our data suggests that overweight children neither prefer high-fat foods nor select foods with much more attention to palatability than non-overweight individuals. These data do not confirm the relationship between diet composition, in particular fat intake, and obesity.

Intake of saturated fatty acids was high compared with guidelines from the National Cholesterol Education Program,22 which suggest intake of no more than 10% of total energy as saturated fatty acids. Saturated fat intakes reported (13.5% of energy) were comparable to literature data.23,24 Cholesterol intake was not higher than the recommendations (300 mg/day).14

Carbohydrate intakes remained lower than RDA.15 Calories from carbohydrate as a percentage of reported energy intake were significantly greater in the non-overweight children compared to the overweight group. Similar results were obtained by Bandini et al.16

By making comparisons to the age+5 rule,22 our results show that the schoolchildren in our sample consumed inadequate dietary fiber (13.2±8.2 g/day). Results of other authors22,25,26 confirm that the schoolchildren did not consume adequate fiber.

Among micronutrients, the absolute intakes of vitamin A and D, calcium, magnesium and zinc were lower than recommendations.15 Other studies have found similar results in vitamin D and calcium intakes.28 The low calcium, vitamin D and A intake may be a consequence of the low consumption of dairy products, as suggest the literature.17 In the present study no significant overweight and non-overweight differences were found for micronutrient intake.

Energy and macronutrients intake during week and weekend days was not different, except for protein, which was greater in the weekdays. This is a consequence of a lower intake of dairy products, fish, meat, eggs and legumes in the weekend days than in the weekdays.

The data suggest the belief that overweight children eat more than non-overweight children is not correct. These findings suggest that the positive energy balance causing overweight is due possibly to a low energy output. However, the sample size studied is small, and future studies should assess a wider sample than that analyzed in the present study.