A 7-day activity diary for assessment of daily energy expenditure validated by the doubly labelled water method in adolescents

Dietary restraint in relation to nutrient intake, physical activity and iron status in adolescent females

AIM

To investigate the prevalence of dietary restraint in a female adolescent population, and to examine the nutritional consequences of dietary restraint and its implications for iron status.

METHODS

A total of 64 adolescent females, aged 14-15 years, were recruited from two all-girl schools in central London. Nutrient intake, body weight, physical activity and iron status were measured. Findings were compared between three groups of subjects classified by dietary restraint.

RESULTS

Adolescents with a higher BMI percentile were more likely to be highly restrained. Scores on the dietary restraint psychometric measures were comparable with other UK studies in this age group. Energy intake was inversely related to dietary restraint (mean energy intake (SE) for each restraint group were: low 8.99 MJ (0.48), medium 7.98 MJ (0.22) and high 7.35 MJ (0.39) P < 0.05); however, a corresponding relationship between dietary restraint and reduced micronutrient intakes was not found. Highly restrained eaters obtained more of their energy intake from bread, fruit and cheese and less from meat, meat products and confectionery. Levels of physical activity were not significantly different between the dietary restraint groups. There was a poor relationship between reported energy intake and estimated energy expenditure. Haematological parameters of iron status were similar across the restraint groups.

CONCLUSIONS

Dietary restraint was exercised by the consumption of a "healthy eating diet". Dieting was not related to a lower iron status; however, the low dietary iron intake and poor iron status of the whole sample is of concern.

Physical activity assessment in children and adolescents

Chronic disease risk factors, including a sedentary lifestyle, may be present even in young children, suggesting that early prevention programmes may be critical to reducing the rates of chronic disease. Accurate assessment of physical activity in children is necessary to identify current levels of activity and to assess the effectiveness of intervention programmes designed to increase physical activity. This article summarises the strengths and limitations of the methods used to evaluate physical activity in children and adolescents. MEDLINE searches and journal article citations were used to locate 59 articles that validated physical activity measurement methods in children and adolescents. Only those methods that were validated against a more stringent measure were included in the review. Based on the definition of physical activity as any bodily movement resulting in energy expenditure (EE), direct observation of the individual's movement should be used as the gold standard for physical activity research. The doubly labelled water technique and indirect calorimetry can also be considered criterion measures for physical activity research, because they measure EE, a physiologic consequence closely associated with physical activity. Devices such as heart rate monitors, pedometers and accelerometers have become increasingly popular as measurement tools for physical activity. These devices reduce the subjectivity inherent in survey methods and can be used with large groups of individuals. Heart rate monitoring is sufficiently valid to use in creating broad physical activity categories (e.g. highly active, somewhat active, sedentary) but lacks the specificity needed to estimate physical activity in individuals. Laboratory and field validations of pedometers and accelerometers yield relatively high correlations using oxygen consumption (r = 0.62 to 0.93) or direct observation (r = 0.80 to 0.97) as criterion measures, although, they may not be able to capture all physical activity. Physical activity has traditionally been measured with surveys and recall instruments. These techniques must be used cautiously in a paediatric population that has difficulty recalling such information. Still, some studies have reported 73.4% to 86.3% agreement between these instruments and direct observation. Future investigations of physical activity instruments should validate the novel instrument against a higher standard. Additional studies are needed to investigate the possibility of improving the accuracy of measurement by combining 2 or more techniques. The accurate measurement of physical activity is critical for determining current levels of physical activity, monitoring compliance with physical activity guidelines, understanding the dose-response relationship between physical activity and health and determining the effectiveness of intervention programmes designed to improve physical activity.

Dietary fat intake in healthy adolescents: inverse relationships between the estimated intake of saturated fatty acids and serum cholesterol

The objective of the present study was to describe the intake of dietary fatty acids among healthy 15-year-old boys and girls and to relate the intake of specific fatty acids and the fatty acid composition of the serum cholesterol esters to serum lipid, apolipoprotein (Apo) and insulin concentrations respectively. Fifty-two girls and forty-two boys were randomly selected from the official population register. Unexpectedly, significant inverse associations were found between the dietary content of saturated fatty acids with a chain length of four to fifteen C atoms, mainly derived from milk fat, as well as the corresponding fatty acids in the serum cholesterol esters, on the one hand and the serum concentrations of cholesterol and ApoB on the other. The estimated dietary intake of 4:0-10:0, 12:0 and 14:0 respectively, were all significantly inversely related to the serum cholesterol (r -0.32, r -0.31, r -0.30, all and ApoB (r -0.42, r -0.42, and r -0.40, all concentrations in girls and 12:0 to the ApoB concentration (r -0.55, in boys. The proportions of 12:0 and 15:0 in the serum cholesterol esters were negatively correlated with the serum cholesterol concentrations in both girls (r -0.34, r -0.32, and boys (r -0.53, r -0.32, and with the ApoB concentrations among boys (r -0.61, r -0.43, It is conceivable that milk fat contains or is associated with some component in the diet, or some other characteristics of the food intake, which counterbalances the expected positive relationships between saturated fat intake and lipid levels.

Prediction of physical activity and physical work capacity (PWC150) in young adulthood from childhood and adolescence with consideration of parental measures

The 12-year prediction of physical activity level and submaximal aerobic fitness observed during young adulthood was quantified from childhood and parental measures. The sample consisted of 153 children and adolescents of the Quebec Family Study who were evaluated at baseline and reassessed 12 years later, as young adults. Physical work capacity at a heart rate of 150 beats x min(-1) (PWC150) was measured using cycle ergometry. A 3-day activity record was used to estimate daily energy expenditure (DEE), inactive time (IA), and time spent in moderate-to-vigorous activity (MVPA). Spearman partial inter-age correlations, controlling for length of follow-up and age at baseline, indicated better tracking for PWC150 (0.24 and 0.46, males and females, respectively) than for indicators of physical activity (0.07 < or = r < or = 0.25, males; 0.06 < or = r < or = 0.22, females). Multiple regression analyses indicated that parental measurements of activity and PWC150 did not add any predictive value, with the exception of paternal DEE, which accounted for 8% of the variance in males. There is moderately high stability of submaximal work capacity and lower tracking of physical activity from childhood and adolescence into young adulthood.

Assessing the influence of physical activity on health and fitness

Increasing rates obesity and related chronic diseases in the United States and other parts of the world appear to be partly attributable to declining levels of physical activity. Given that adult obesity and chronic diseases often have their origins in childhood, there is a critical need to better understand how activity and fitness levels in childhood and adolescence shape health status in adulthood. The four papers in this series on physical activity draw on several longitudinal studies to examine the relationships between levels of physical activity and health-related fitness in childhood and adolescence to those in adulthood. These studies consistently demonstrate that adult activity levels and associated health outcomes are only modestly correlated with activity and fitness measures from childhood and adolescence. However, it appears that the methodological limitations in measuring activity levels may result in an underestimation of the importance of the influence of physical activity on health. Newer methods of measuring activity and energy expenditure offer to substantially improve our understanding of the influence of activity patterns on human health and fitness. Such information is necessary for promoting lifestyle changes that will reduce the risks of obesity and other chronic diseases.

Physical activity, physical fitness, and coronary heart disease risk factors in youth: the Québec Family Study

OBJECTIVE

The relationships between physical activity, fitness, and CHD risk factors were investigated in 342 males and 268 females 9-18 years of age.

METHODS

Daily energy expenditure, moderate to vigorous physical activity, inactivity, and television viewing time were estimated. Indicators of physical fitness included submaximal work capacity, quadriceps muscle strength, sit-ups, and the sum of six skinfolds. Risk factors included mean arterial blood pressure and fasting blood levels of triglycerides, LDL-cholesterol, HDL-cholesterol, and glucose.

RESULTS

Canonical correlations between activity and risk factor profiles range from 0.22 to 0.45, while those between fitness and risk factor profiles range from 0.34 to 0.55, indicating that 5 to 20% and 11 to 30% of the variance in the risk profile is explained by activity and fitness, respectively.

CONCLUSION

The results suggest that both physical fitness and level of habitual physical activity are strongly associated with CHD risk factors in this sample of youth.

Total daily energy expenditure and patterns of physical activity in adolescents assessed by two different methods

Minute-by-minute heart rate monitoring and an activity diary were used simultaneously during three days in 30 randomly selected adolescents (16 boys, 14 girls; mean age 15.0+/-1.0). Total daily energy expenditure (TDEE) and its components (energy expenditure during sleep, during rest and in physical activity) and times spent at different intensity levels (sedentary, light, moderate physical activity and vigorous physical activity) were compared. TDEE from heart rate monitoring averaged 10.9+/-2.7 MJ x d(-1) compared to 11.3+/-2.3 MJ x d(-1) from the activity diary (NS). The limits of agreement (mean+/-2 SD) were -3.54 MJ x d(-1) and 2.74 MJ x d(-1). There was no significant difference for any of the TDEE components between the methods (MANOVA). A significant method effect (P<0.001) was observed for time spent in sedentary and light physical activity (MANOVA). No significant difference was observed for time spent in moderate and vigorous physical activity. According to this, heart rate monitoring and activity diary are comparable for group assessment of TDEE and its components, and for estimating time spent in moderate and vigorous physical activity. The activity diary underestimated time spent in moderate and vigorous physical activity for inactive subjects and consequently overestimated highly active subjects.

Food habits and energy and nutrient intake in Swedish adolescents approaching the year 2000

In 1993-94 a nutritional survey of 15-year-old adolescents was carried out in Uppsala, a university city in eastern Sweden, and in Trollhättan, an industrial town in the western part of the country. The study was the beginning of a longitudinal nutritional survey of 193 boys and 218 girls randomly selected from the official population register. The dietary methods used were a food frequency questionnaire (FFQ) and a combined estimated and weighed 7-day dietary record. According to the FFQ both boys and girls consumed cereals, butter or margarine and something from the group meat/fish/eggs every day. Milk, milk products, sweets and snacks were consumed more than once per day. Vegetables and fruit/roots were consumed less often. There was relatively good correlation between the FFQ and the 7-day record results. The mean daily energy intakes of the 15-year-old boys and girls were 10.2 and 8.3 MJ, respectively, in Uppsala, and 9.8 and 7.4 MJ in Trollhättan. The mean daily intakes of sucrose were 74 and 58 g in boys and 64 and 52 g in girls. The average daily dietary fibre intake was 1.8 g/MJ. The daily intake of energy obtained from breakfast was 18% on weekdays and 22% on weekends; 18 and 11% from prepared lunch; 24 and 30% from dinner, 21 and 14% from light meals; and 16 and 28% from snacks, in Uppsala and Trollhättan respectively. The lowest energy intake from a prepared lunch meal was noted during weekends. On both weekdays and weekends, considerable energy was obtained from light meals and snacks. However, nearly 40% of the girls and 28% of the boys had an energy intake from fat of < 30 energy%. The mean intakes of vitamin D and selenium and, in the case of girls, iron and zinc, were below the official Swedish Nutrition Recommendations. The daily median intake of iron was 18.7 mg in boys and 14.1 mg in girls. The iron intakes varied between 6 and 35 mg per day. Low serum ferritin concentrations, defined as s-ferritin < 12 micrograms/L, were found in 7 boys (3.7% and in 29 girls (13.9%). Significant negative correlations were found between smoking and frequency of consumption of vegetables, roots, fruits and meat. A negative correlation was also found between smoking and the intake of energy and a number of nutrients. Socioeconomic factors seem to be less important for the food habits of teenagers than for those noted during childhood. Only frequent consumption of vegetables was positively correlated to the mothers' educational level.