Olejko 1984.

Study characteristics
Methods	RCT. Parallel design with 3 treatment arms. Duration: 6 weeks. Location: single centre in the USA.
Participants	Inclusion criteria: adults awaiting elective orthognathic surgery. Exclusion criteria: not specified. Number randomised: 24 participants (intervention group 1, n = 8; intervention group 2, n = 8; control group, n = 8). 100% follow‐up. Gender split: 12 males, 12 females. Age: mean (SD), 22.8 (6.1) years. Nutritional status: 12 of 24 participants had a weight below IBW at study inclusion. Mean BMI can be calculated from individual participant data (mean BMI 22).
Interventions	Intervention (intervention group 1): participants received dietary advice and ONS in the form of dietary instruction and an oral nutritional supplement (1.5 kcal/mL) to provide 50% of energy requirements. Intervention (intervention group 2): participants received dietary advice and ONS in the form of dietary instruction, an oral nutritional supplement (1.5 kcal/mL) to provide 50% of energy requirements and a nutritional supplement to take preoperatively. Control: participants received dietary advice alone in the form of dietary instruction given verbally and in writing.
Outcomes	Survival*, body weight*, MUAC*, MAMC*, TSF*, serum chemistry and creatinine height index, macro and micronutrient intake.
Publication details	Language: English. Funding: not reported. Publication status: peer‐reviewed journal.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as randomised, method not reported.
Allocation concealment (selection bias)	Unclear risk	Method not reported.
Blinding (performance bias and detection bias) Clinical outcomes	Low risk	Not reported, but the nature of the study suggests that the study was unblinded. However, it is unlikely that knowing groups assignment would have influenced clinical outcomes.
Blinding (performance bias and detection bias) Functional outcomes	High risk	Not reported, but the nature of the study suggests that the study was unblinded. Functional outcomes could have been influenced by lack of blinding.
Blinding (performance bias and detection bias) Nutritional outcomes	High risk	Not reported, but the nature of the study suggests that the study was unblinded. Nutritional outcomes could have been influenced by lack of blinding.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not blinded and likely that researchers and participants were aware of group allocation as this was a nutritional intervention. It is possible that assessment of some outcomes was influenced by lack of blinding.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judged to be unclear because of low risk for clinical outcomes and high risk for functional and nutritional outcomes.
Incomplete outcome data (attrition bias) All outcomes	Low risk	100% follow‐up.
Selective reporting (reporting bias)	High risk	No study protocol identified, thus unable to judge whether all planned outcomes were reported. All outcomes were reported but using general statements about change rather than numerical presentation e.g. 'the pre‐load group reported an average weight gain of 3.1% during the one month pre‐operative period, which was significantly greater (P < 0.05) than that of the other two groups'. No data are available from the authors therefore unclear risk of bias due to partial reporting.
Other bias	Unclear risk	Baseline variables not given, not sure if groups similar at baseline.