| Methods |
Study design: prospective cohort study.
Analysis methods for cohorts: linear regression models used to estimate effects of diet and physical activity on annual changes in adiposity with 1‐year change in BMI and weight as the continuous variables. Models adjusted for ethnicity, baseline BMI, annual change in height, menstrual history in girls, pubertal stage and age.
How were missing data handled? Number of children who did not return at 1‐year follow‐up (22.8%, 3819/16771) and 3‐year follow‐up (23.5%, 3942/16771). Data on BMI, dietary intake and physical activity compared between children who did not return the questionnaires and children who did. Authors indicated that there did not seem to be bias related to dietary intake or adiposity, but children lost to follow‐up were older and more physically active.
Number of study contacts: 2 (baseline, 1 year' follow‐up, Berkey 2000); 4 (baseline, 1, 2 and 3 years' follow‐up, Berkey 2005).
Period of follow‐up (total period of observation): 1 year (Berkey 2000); 3 years (Berkey 2005).
Period of recruitment: 1996.
Sample size justification adequately described? No.
Sampling method: convenience sample. Participants were children of mothers who were nurses and participated in Nurses' Health Study II. Letters sent to mothers explaining goals of new study and requesting their consents.
Study objective: to examine role of physical activity, inactivity and DPs on annual weight changes among preadolescents and adolescents, taking growth and development into account.
Study population: preadolescents and adolescents aged 9‐14 years in the USA. |
| Participants |
Baseline characteristics (reported for 1 overall group)
Age (range eligible for inclusion in years): 9‐14. Sex: 53.5% girls. Ethnicity: 94.7% white, 0.9% black, 1.5% Hispanic, 1.5% Asian, 1.4% other. Education: NR. Income: NR. Pubertal stage: Tanner stage: NR. Girls begun menstrual cycles at: 9 years of age, 0.3%; 10 years, 2.4%; 11 years, 11.6%; 12 years, 36.5%; 13 years, 69.4%; 14 years, 89.4%. Parental BMI: NR. Child total energy (kJ): 9 years: overall (n = 1962) 9196 (SD 2680); girls (n = 1029) 8812 (SD 2661); boys (n = 933) 9619 (SD 2636); 10‐years: overall (n = 3226) 8975 (SD 2750); girls (n = 1698) 8569 (SD 2686); boys (n = 1528) 9427 (SD 2749); 11 years: overall (n = 3338) 9014 (SD 2942); girls (n = 1730) 8510 (SD 2690); boys (n = 1608) 9556 (SD 3100); 12 years: overall (n = 3067) 9034 (SD 2958); girls (n = 1671) 8577 (SD 2782); boys (n = 1396) 9581 (SD 3067); 13 years: overall (n = 2779) 9177 (SD 3049); girls (n = 1497) 8669 (SD 2828); boys (n = 1282) 9770 (SD 3188); 14 years: overall (n = 2399) 9316 (SD 3029); girls (n = 1355) 8740 (SD 2682); boys (n = 1044) 10063 (SD 3280). Child total fat (g): 9 years: overall (n = 1962) 74.3 (SD 11.54); girls (n = 1029) 70.4 (SD 10.4); boys (n = 933) 78.6 (SD 11.2); 10 years: overall (n = 3226) 74.07 (SD 11.85); girls (n = 1698) 70.0 (SD 10.8); boys (n = 1528) 78.6 (SD 11.3); 11 years: overall (n = 3338) 73.99 (SD 12.09); girls (n = 1730) 69.7 (SD 11.1); boys (n = 1608) 78.6 (SD 11.4); 12 years: overall (n = 3067) 73.4 (SD 12.5); girls (n = 1671) 68.9 (SD 11.2); boys (n = 1396) 78.8 (SD 11.7); 13 years: overall (n = 2779) 73.08 (SD 12.9); girls (n = 1497) 68.1 (SD 11.6); boys (n = 1282) 78.9 (SD 11.9); 14 years: overall (n = 2399) 71.5 (SD 13.02); girls (n = 1355) 66.5 (SD 12.0); boys (n = 1044) 78.0 (SD 11.3). Child total protein: NR. Child total CHO: NR. Child physical activity (hours/day): 9 years: overall (n = 1962) 1.88 (SD 1.17); girls (n = 1029) 1.65 (SD 1.03); boys (n = 933) 2.14 (SD 1.26); 10 years: overall (n = 3226) 2.03 (SD 1.2); girls (n = 1698) 1.80 (SD 1.11); boys (n = 1528) 2.29 (SD 1.25); 11 years: overall (n = 3338) 2.23 (SD 1.25); girls (n = 1730) 2.01 (SD 1.19); boys (n = 1608) 2.47 (SD 1.26); 12 years: overall (n = 3067) 2.44 (SD 1.31); girls (n = 1671) 2.29 (SD 1.28); boys (n = 1396) 2.62 (SD 1.33); 13 years: overall (n = 2779) 2.62 (SD 1.35); girls (n = 1497) 2.47 (SD 1.34); boys (n = 1282) 2.79 (SD 1.34); 14 years: overall (n = 2399) 2.64 (SD 1.34); girls (n = 1355) 2.58 (SD 1.36); boys (n = 1044) 2.71 (SD 1.32). Child physical inactivity or screen time or both (hours/day): 9 years: overall (n = 1962) 3.77 (SD 2.05); girls (n = 1029) 3.42 (SD 1.94); boys (n = 933) 4.15 (SD 2.10); 10 years: overall (n = 3226) 3.92 (SD 2.17); girls (n = 1698) 3.49 (SD 1.99); boys (n = 1528) 4.39 (SD 2.27); 11 years: overall (n = 3338) 4.04 (SD 2.24); girls (n = 1730) 3.65 (SD 2.07); boys (n = 1608) 4.45 (SD 2.33); 12 years: overall (n = 3067) 4.21 (SD 2.28); girls (n = 1671) 3.86 (SD 2.14); boys (n = 1396) 4.62 (SD 2.38); 13 years: overall (n = 2779) 4.26 (SD 2.31); girls (n = 1497) 3.80 (SD 2.15); boys (n = 1282) 4.80 (SD 2.38); 14 years: overall (n = 2399) 4.07 (SD 2.36); girls (n = 1355) 3.55 (SD 2.17); boys (n = 1044) 4.75 (SD 2.43). Child CVD risk (excluding fatness): NR. Child body fatness, weight (kg): 9 years: overall (n = 1962) 37.72 (SD 7.12); girls (n = 1029) 32.98 (SD 6.77); boys (n = 933) 34.55 (SD 7.41); 10 years: overall (n = 3226) 37.28 (SD 8.29); girls (n = 1698) 36.79 (SD 8.25); boys (n = 1528) 37.82 (SD 8.31); 11 years: overall (n = 3338) 41.78 (SD 9.26); girls (n = 1730) 41.58 (SD 9.22); boys (n = 1608) 42.0 (SD 9.29); 12 years: overall (n = 3067) 47.64 (SD 10.43); girls (n = 1671) 47.55 (SD 10.01); boys (n = 1396) 47.75 (SD 10.91); 13 years: overall (n = 2779) 53.1 (SD 11.18); girls (n = 1497) 52.31 (SD 10.1); boys (n = 1282) 53.93 (SD 12.26); 14 years: overall (n = 2399) 57.62 (SD 11.24); girls (n = 1355) 55.04 (SD 9.67); boys (n = 1044) 60.95 (SD 12.22). Child body fatness, BMI (kg/m2): 9 years: overall (n = 1962) 17.61 (SD 2.87); girls (n = 1029) 17.47 (SD 2.84); boys (n = 933) 17.77 (SD 2.9); 10 years: overall (n = 3226) 18.14 (SD 3.1); girls (n = 1698) 18.02 (SD 3.1); boys (n = 1528) 18.28 (SD 3.1); 11 years: overall (n = 3338) 18.63 (SD 3.12); girls (n = 1730) 18.48 (SD 3.06); boys (n = 1608) 18.79 (SD 3.17); 12 years: overall (n = 3067) 19.42 (SD 3.28); girls (n = 1671) 19.36 (SD 3.26); boys (n = 1396) 19.5 (SD 3.3); 13 years: overall (n = 2779) 20.08 (SD 3.29); girls (n = 1497) 20.05 (SD 3.17); boys (n = 1282) 20.11 (SD 3.42); 14 years: overall (n = 2399) 20.65 (SD 3.15); girls (n = 1355) 20.52 (SD 3.09); boys (n = 1044) 20.82 (SD 3.22). Child physical activity (number of gym class/week): 9 years: overall (n = 1962) 2.1 (SD 1.1); girls (n = 1029) 2.1 (SD 1.1); boys (n = 933) 2.1 (SD 1.1); 10 years: overall (n = 3226) 2.15 (SD 1.1); girls (n = 1698) 2.1 (SD 1.1); boys (n = 1528) 2.2 (SD 1.1); 11 years: overall (n = 3338) 2.5 (SD 1.4); girls (n = 1730) 2.5 (SD 1.4); boys (n = 1608) 2.5 (SD 1.4); 12 years: overall (n = 3067) 2.9 (SD 1.6); girls (n = 1671) 2.9 (SD 1.6); boys (n = 1396) 2.9 (SD 1.6); 13 years: overall (n = 2779) 3.05 (SD 1.6); girls (n = 1497) 3.0 (SD 1.6); boys (n = 1282) 3.1 (SD 1.6); 14 years: overall (n = 2399) 3.06 (SD 1.8); girls (n = 1355) 3.1 (SD 1.8); boys (n = 1044) 3.0 (SD 1.8).
Included criteria: children aged in 9‐14 years of Nurses' Health Study II participants with completed questionnaires at baseline.
Excluded criteria: children with misreporting data of dietary intake (500 kcal/day or > 5000 kcal/day), physical activity (> 40 hours/week), screen time (> 80 hours/week), height (> 3 SD), BMI (12 kg/m2 or > 3 SD).
Brief description of participants: children aged 9‐14 years residing in 50 states of the USA whose mothers were nurses and participated in the Nurses' Health Study II.
Total numbers completed in cohort study: 10,769 included in the data analysis out of 12,952 children who returned after 1 year' follow‐up). Number of children included in data analysis at 3 years NR, although 12,829 children returned after 3 years' follow‐up.
Total numbers enrolled in cohort study: 16,771. Eligible sample consisted of 26,765 children (of 18,526 mothers in Nurses' Health Study II). |
| Interventions |
Description of exposure for cohorts
Time span: 1 year (Berkey 2000), 3 years (Berkey 2005). Dietary assessment method: self‐administered, validated semi‐quantitative FFQ). Frequency: single FFQ at baseline and 1‐year follow‐up (Berkey 2000); single FFQ at baseline and each of 3 years' follow‐up (Berkey 2005).
See Table 9; Table 10; Table 11; Table 12; Table 13; Table 14; Table 15; Table 16; Table 17; Table 18 for details of total fat intake exposure per outcome. |
| Outcomes |
Weight
BMI
|
| Identification |
Sponsorship source: grant DK46834 from the National Institutes of Health and, in part, by Kellogg's.
Country: USA.
Setting: communities in 50 states.
Comments: The Growing Up Today Study.
Author's name: Catherine S Berky.
Institution: Channing Laboratory, Department of Medicine, Brigham Women's Hospital and Harvard Medical School.
Email: catherine.berky@channing.harvard.edu.
Declaration of interests: no.
Study ID: Berkey 2000.
Type of record: journal article. |
| Notes |
We contacted the authors to request relevant numerical outcome data, since they only reported the following sentence about total fat intake and weight in the text: ".... and no fat (dairy, vegetable, or other) intake was significantly associated with weight gain after energy adjustment, nor was total fat intake." We had not received a response by time of publication. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Were adequate outcome data for cohorts available?
All outcomes |
High risk |
High attrition (35.8% (6002/16771) over 1 year). Data on BMI, dietary intake and physical activity compared between children who did not return the questionnaires and children who did. The authors indicated that there did not seem to be bias related to dietary intake or adiposity, but children lost to follow‐up were older and more physically active. |
| Was there matching of less‐exposed and more‐exposed participants for prognostic factors associated with outcome or were relevant statistical adjustments done?
All outcomes |
Low risk |
Data analyses adjusted for age, gender, ethnicity, pubertal stage while physical activity and total energy intake were included in the model. Parental BMI and SES not adjusted for. Likely that children had similar family income level as their mothers were nurses. |
| Did the exposures between groups differ in components other than only total fat?
All outcomes |
Low risk |
|
| Can we be confident in the assessment of outcomes?
All outcomes |
High risk |
Height and weight were self‐reported although specific instructions on how to measure height and weight were given to participants. |
| Can we be confident in the assessment of exposure?
All outcomes |
Low risk |
Repeated self‐administered, semi‐quantitative FFQs used to assess dietary intake. Participants with dietary misreporting were excluded from data analyses. |
| Can we be confident in the assessment of presence or absence of prognostic factors?
All outcomes |
Low risk |
Repeated assessments of physical activity, screening time and pubertal stage conducted using validated questionnaires. |
| Was selection of less‐exposed and more‐exposed groups from the same population?
All outcomes |
Low risk |
Participants selected for 1 cohort study. |
