Total fat intake and body weight in children (cohort studies)a,b
Patient or population: boys and girls aged 24 months to 18 years Setting: communities, schools, households, healthcare centres in high‐income countries Exposure: total fat intake
Outcomes	No of studies (No of participants)	Impact	Quality	What happens
Weight (kg) Follow‐up: 2 to 5 years	4 cohort studies (13,802)	2 studies that adjusted for TE intake: After 3 years, "Dairy fat was not a stronger predictor of weight gain than other types of fat, and no fat (dairy, vegetable, or other) intake was significantly associated with weight gain after energy adjustment, nor was total fat intake;" no numerical results reported. After 3 years, for every 1% increase in TE intake from total fat of children, weight will decrease by 0.0011 kg. 2 studies that did not adjust for TE intake: After 4 years, weight of children with low‐fat intake (< 30%TE) will increase by 8.1 kg on average, and by 8.9 kg on average in children with high‐fat intake (> 35%TE). After 2 years, children with low‐fat intake (≤ 30%TE) will gain on average 0.2 kg per year more than children with high‐fat intakes (> 30%TE)	⊕⊝⊝⊝ Very low1,2	When adjusted for TE, we were uncertain whether fat intake was associated with weight in children over 2 to 5 years. When not adjusted for TE, we were uncertain whether lower fat was associated with weight in children over 2 to 5 years.
Follow‐up: 5 to 10 years	1 cohort study(126)	1 study that did not adjust for TE intake: After 6 years, weight of children with low‐fat intake (< 30%TE) will increase by 16.8 kg on average, and by 13.9 kg on average in children with high‐fat intake (> 35%TE)	⊕⊝⊝⊝ Very low3,4,5,6	We were uncertain whether fat intake was associated with weight over 5 to 10 years (1 study).
BMI (kg/m2, kg/m2per year, z‐score, percentile) Follow‐up: 2 to 5 years	7 cohort studies (3143)	4 studies that adjusted for TE intake: After 3 years, for every 1% increase in energy intake from total fat, BMI will decrease by 0.63 z‐score in boys but increase by 0.07 z‐score in girls. "Dietary factors were not associated with BMI across the three study years." After 3 years, for every 1% increase in energy intake from total fat, BMI will decrease by 0.00008 kg/m2. After 4 years, increase in the total fat intake, will increase BMI by 0.087 z‐score. The model explained 48% of variance in the change of BMI z‐score. 2 studies that did not adjust for TE intake: After 2.08 years, low‐fat intake (≤ 30%TE) will result in a 0.02 kg/m2 per year greater increase in BMI on average, compared to high‐fat intake (> 30%TE). After 3 years, for every 1% increase in energy intake from total fat, BMI will decrease by 0.01 percentile in girls. 1 study where TE adjustment was not applicable, as TE was part of exposure: After 3 years, for every 1 z‐score increase in the energy‐dense, high‐fat and low‐fibre dietary pattern, BMI will increase by 0.03 z‐score in boys and by 0.99 z‐score in girls. After 3 years, the ratio of odds for being overweight/obese was 1.04 greater in boys and 1.02 greater in girls with higher dietary pattern z‐scores, compared to the odds in boys and girls with lower dietary pattern z‐scores.	⊕⊝⊝⊝ Very low6,7,8	We were uncertain whether fat intake was associated with BMI in children over 2 to 10 years or > 10 years.
Follow‐up: 5 to 10 years	4 cohort studies (1158)	3 studies that adjusted for TE intake: After 6 years, for every 1% increase in energy intake from total fat, BMI will decrease by 0.011 z‐score in boys but increase by 0.005 z‐score in girls. After 9 years, increase in the total fat intake will increase BMI by 0.122 z‐score. After 10 years, for every 1% increase in energy intake from total fat, BMI will increase by 0.029 kg/m2 in white girls and by 0.012 kg/m2 in black girls. 1 study that did not adjust for TE intake: After 6 years, for every 1 g increases in the fat intake, BMI will increase by 0.01 kg/m2	⊕⊝⊝⊝ Very low6,9
Follow‐up: > 10 years	2 cohort studies (330)	1 study that adjusted for TE intake: After 13 years, increase in the total fat intake will increase BMI by 0.16 z‐score. 1 study that did not adjust for TE intake: After 17 years, on average BMI decreased 0.13 z‐score in the low‐fat (32%TE) group while increased 0.04 z‐score in the high‐fat (40%TE) group.	⊕⊝⊝⊝ Very low6,10
LDL‐C (mmol/L) Follow‐up: 2 to 5 years	1 cohort study (1163)	1 study where TE adjustment not applicable, as TE was part of exposure: After 3 years, for every 1 z‐score increase in the energy‐dense, high‐fat and low‐fibre dietary pattern, LDL‐C will increase by 0.001 mmol/L in boys and 0.04 mmol/L in girls	⊕⊝⊝⊝ Very low4,5,6,11	We were uncertain whether fat intake was associated with LDL‐C in children over 2 to 5 years (1 study).
HDL‐C (mmol/L) Follow‐up: 2 to 5 years	2 cohort studies (1393)	1 study that adjusted for TE intake: After 3 years, for every 1% increase in energy intake from total fat, HDL‐C will decrease by 0.21 mmol/L in girls. 1 study where TE adjustment not applicable, as TE was part of exposure: After 3 years, for every 1 z‐score increase in the energy‐dense, high‐fat and low‐fibre dietary pattern, HDL‐C will decrease by 0.002 mmol/L in boys but increase by 0.02 mmol/L in girls.	⊕⊕⊝⊝ Low11,12	When adjusted for TE, fat intake may be inversely associated with HDL‐C in girls over 2 to 5 years (1 study). When not adjusted for TE, fat intake may make little or no difference to HDL‐C in girls over 2 to 5 years (1 study).
Triglycerides (mmol/L) Follow‐up: 2 to 5 years	1 cohort study (1163)	1 study where TE adjustment not applicable, as TE was part of exposure: After 3 years, for every 1 z‐score increase in the energy‐dense, high‐fat and low‐fibre dietary pattern, triglycerides will increase by 1% in either boys or girls.	⊕⊝⊝⊝ Very low4,5,6,11	We were uncertain whether fat intake was associated with triglycerides in children over 2 to 5 years (1 study).
Height (cm) Follow‐up: 2 to 5 years	3 cohort studies (973)	1 study that adjusted for TE intake: After 3 years, for every 1% increase in energy intake from fat, height in children will decrease by 0.0009 cm on average. 2 studies that did not adjust for TE intake: After 2 years, low‐fat intake (≤ 30%TE) will result in a 0.2 cm per year greater increase in height on average compared to high‐fat intake (> 30%TE). After 4 years, on average children in low‐fat intake (< 30%TE) gain 27.9 cm in height, while children in high‐fat intake (> 35%TE) gain 28.3 cm in height.	⊕⊝⊝⊝ Very low6,10	We were uncertain whether fat intake was associated with height in children over 2 to 10 years.
Follow‐up: 5 to 10 years Age at baseline: 2 years	1 cohort study (126)	1 study that did not adjust for TE intake: At 6 years, on average children in low‐fat intake (< 30%TE) gain 44.9 cm in height while children in high‐fat intake (> 35%TE) gain 40.3 cm in height.	⊕⊝⊝⊝ Very low3,4,5,6
BMI: body mass index; HDL‐C: high‐density lipoprotein cholesterol; LDL‐C: low‐density lipoprotein cholesterol; MD: mean difference; TE: total energy. aNotes: Some cohort studies reported more than one eligible analysis for the same outcome (e.g. BMI as continuous or binary outcome) or different measures of exposure (e.g. fat intake as continuous %TE or as binary classification of less‐exposed vs more‐exposed). In these cases, we selected outcomes and exposure measures so as not to use the same study sample of participants more than once per outcome and time point range in the table. b No studies looked at weight at > 10 years; LDL‐C, HDL‐C and triglycerides at 12 months, 1 to 2 years and > 5 years, and height at > 10 years. For all outcomes, there were too few studies to assess publication bias.
GRADE Working Group grades of evidence High quality: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate quality: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low quality: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low quality: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.