BDIT Pilot Studies 1996.

Methods	RCT
Participants	Women with mammographic dysplasia (Canada) CVD risk: low Control: 147 randomised, 78 analysed Intervention: 148 randomised, 76 analysed Mean years in trial: control 7.5, intervention 6.8 % male: 0 Age: mean control 45, intervention 44 (all > 30) Baseline BMI: mean intervention 24.3 (SD 3.8), control 24.3 (SD 3.6)
Interventions	Reduced fat intake vs usual diet Control aims: healthy diet advice, no alteration in dietary fat advised, aim to maintain weight Intervention aims: total fat 15%E, replace fat by complex CHO, aim to maintain weight Control methods: seen for advice once every 4 months for 12 months Intervention methods: seen for advice once a month for 12 months Weight goal: low fat group ‐ "isocaloric exchange of complex carbohydrate for fat. We tried to maintain an isocaloric diet to avoid weight loss...". Not discussed for control group Total fat intake (at 9.2 years): low fat 31.7 (SD 7.3) %E, control 35.3 (SD 5.6) %E Saturated fat intake (at 9.2 years): low fat 10.6 (SD 4.6) %E, control 12.3 (SD 4.6) %E Style: diet advice Setting: community
Outcomes	Stated trial outcomes: dietary fat, serum cholesterol Available outcomes: weight, BMI, total and HDL cholesterol
Notes	Weight data available for 1 year, 2 years and 9 years. Unclear whether participants were still in the trial by 9 years, so 2‐year data used in main analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"randomly allocated"
Allocation concealment (selection bias)	Unclear risk	Randomisation not described
Blinding (performance bias and detection bias) All outcomes	High risk	Participants not blinded, but outcome assessors blinded to intervention
Incomplete outcome data (attrition bias) All outcomes	High risk	141 of 295 (48%) lost over 8 years (> 5% per year)
Selective reporting (reporting bias)	Unclear risk	Protocol not seen
Other bias	Low risk
Free of systematic difference in care?	High risk	Minor: women in intervention group seen more frequently. See 'Control methods' and 'Intervention methods' in the 'Interventions' section above
Free of dietary differences other than fat?	Low risk	See 'Control aims' and 'Intervention aims' in the 'Interventions' section above