Kendell 1982.

Study characteristics
Methods	RCT. Parallel design with 2 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 n = 12; control group n = 12). Attrition: 100% follow‐up. Gender split: 5 males and 19 females. Age: mean (SD) 25 (8.1) years. Nutritional status: 12 out of 24 participants had a weight below IBW at inclusion.
Interventions	Intervention group: 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 calculated energy requirements. Control group: participants received dietary advice alone in the form of dietary instruction given verbally and in writing.
Outcomes	Survival*, body weight*, MAUC, MAMC*, TSF*, serum chemistry and creatinine height index, macro and micronutrient intake, length of hospital stay.
Publication details	Language: English Funding: Publication status: peer‐reviewed journal
Notes	Data not available from authors.
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	Unclear risk	Not reported.
Blinding (performance bias and detection bias) Functional outcomes	Unclear risk	Not reported
Blinding (performance bias and detection bias) Nutritional outcomes	Unclear risk	Not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not described 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	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	100% follow‐up.
Selective reporting (reporting bias)	High risk	All outcomes reported but using general statements e.g. 'at each time interval, there were no statistically significant differences in body weight, MAC, TSF and creatinine height index between the experimental and control groups'. Data presented in table as % deficit and data not available from the authors, therefore risk of bias due to partial reporting.
Other bias	Unclear risk	Baseline variables not given, no information available from authors, not sure if groups similar at baseline.