Ley 2004.

Study characteristics
Methods	RCT Summary risk of bias: low
Participants	People with impaired glucose intolerance or high normal blood glucose (New Zealand) CVD risk: moderate Control: unclear how many randomised (176 between both groups), unclear how many analysed (112 between both groups at 5 years) Intervention: as above Mean years in trial: 4.1 over whole trial % male: control 80%, intervention 68% Age: mean control 52.0 (SE 0.8), intervention 52.5 (SE 0.8) Ethnicity: European 67% int, 77% control, Maori 11% int, 7% control, Pacific islander 20% int, 13% control, Other 3% int, 4% control (outcomes not provided by ethnicity) Statins use allowed? Unclear % taking statins: Not reported
Interventions	Reduced fat vs usual diet Control aims: usual diet Intervention aims: reduced fat diet (no specific goal stated) Control methods: usual intake plus general advice on healthy eating consistent with the New Zealand guidelines and standard dietary information for people with nutrition‐related problems upon entering the trial Intervention methods: monthly small group meetings to follow a 1‐year structured programme aimed at reducing fat in the diet, includes education, personal goal‐setting, self‐monitoring Total fat intake, %E (at 1 year): int 26.1 (SD 7.7), cont 33.6 (SD 7.8) (mean difference ‐7.50, 95% CI ‐10.37 to ‐4.63) significant reduction Intervention delivered in small face‐to‐face groups but unclear by whom Saturated fat intake, %E (at 1 year): cont 13.4 (SD 4.7), int 10.0 (SD 4.2) (mean difference ‐3.40, 95% CI ‐5.05 to ‐1.75) significant reduction PUFA intake, %E (at 1 year): cont 4.8 (SD 1.6), int 4.0 (SD 1.4) (mean difference ‐0.80, 95% CI ‐1.36 to ‐0.24) significant reduction PUFA n‐3 intake: not reported PUFA n‐6 intake: not reported MUFA intake, %E (at 1 year): cont 11.8 (SD 3.1), int 8.9 (SD 2.8) (mean difference ‐2.90, 95% CI ‐3.99 to ‐1.81) significant reduction CHO intake, %E (at 1 year): cont 45.8 (SD 10.9), int 54.2 (SD 10.5) (mean difference 8.40, 95% CI 4.44 to 12.36) significant increase Protein intake, %E (at 1 year): cont 16.6 (SD 3.9), int 18.4 (SD 3.5), (mean difference 1.80, 95% CI 0.43 to 3.17) significant increase Trans fat intake: not reported Replacement for saturated fat: carbohydrate and protein (based on dietary achievements) Style: diet advice Setting: community
Outcomes	Stated trial outcomes: lipids, glucose, blood pressure Data available on total mortality? yes Cardiovascular mortality? yes Events available for combined cardiovascular events: MI, angina, stroke, heart failure Secondary outcomes: total MI, stroke, cancer diagnoses, cancer deaths, CHD events (MI or angina) Tertiary outcomes: weight, total, LDL and HDL cholesterol, TGs, BP
Notes	Study duration over 4 years Study aim was to reduce total fat (not saturated fat), but saturated fat intake in the intervention group was significantly lower than in the control group. SFA reduction achieved Total serum cholesterol, difference between intervention and control, mmol/L: ‐0.05 (95% CI ‐0.46 to 0.36), NO statistically significant reduction and smaller than 0.20 Trial dates: Recruitment 1988 to 1990 Funding: National Heart Foundation of New Zealand, Auckland Medical Research Foundation, Lotteries Medical Board and the Health Research Council of New Zealand Declarations of Interest of primary researchers: none stated, all authors worked for academic or health institutions
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Unmarked opaque envelopes were opened by the person recruiting, unable to alter allocation later (trial author stated in their reply to us that randomisation and preparation of the envelopes was by people not involved in recruitment).
Allocation concealment (selection bias)	Low risk	Unmarked opaque envelopes were opened by the person recruiting, unable to alter allocation later.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Dietary advice, not blinded
Blinding of outcome assessment (detection bias) CVD outcomes	Low risk	Trial authors stated that outcome assessors were blinded.
Blinding of outcome assessment (detection bias) All‐cause mortality	Low risk	Blinding is not relevant in assessment of mortality.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear, deaths, cancer and CV events are dropouts, trialists were asked for data ‐ unclear if any data missing
Selective reporting (reporting bias)	Low risk	Not relevant for primary and secondary outcomes as we asked all trialists for data
Free of systematic difference in care?	High risk	See control and intervention methods in the Interventions section of the table of Characteristics of included studies
Stated aim to reduce SFA	High risk	Aim to reduce SFA not stated
Achieved SFA reduction	Low risk	SFA reduction achieved
Achieved TC reduction	High risk	TC fall small (0.05 mmol/L only) and not statistically significant
Other bias	Low risk	None noted