Abstract: Forty-five studies (3186 participants) met the inclusion criteria; (dietary advice compared with: no advice (1053 participants); with oral nutritional supplements (332 participants); with dietary advice and oral nutritional supplements (731 participants); and dietary advice plus oral nutritional supplements compared with no additional intervention (1070 participants). Follow-up ranged from 18 days to 24 months. No comparison showed a significant difference between groups for mortality or morbidity. There was a significant change in weight found between groups when comparing dietary advice to no advice for interventions lasting greater than 12 months, mean difference 3.75 kg (95% confidence interval 0.97 to 6.53), and when all studies were combined, mean difference 1.47 kg (95% confidence interval 0.32 to 2.61) although there was significant heterogeneity in the combined analysis (I2 = 90%). Similar improvements in weight were found for the comparison of dietary advice with nutritional supplements if required versus no advice, mean difference 2.20 kg (95% confidence interval 1.16 to 3.25). Dietary advice compared with no advice was also associated with significantly improved mid-arm muscle circumference when all studies were combined, but with moderate heterogeneity, mean difference 0.81 mm (95% confidence interval 0.31 to 1.31). Dietary advice given with nutritional supplements compared with dietary advice alone resulted in improvements in: mid-arm muscle circumference, mean difference -0.89 mm (95% confidence interval -1.35 to -0.43); triceps skinfold thickness, mean difference -1.22 mm (95% confidence interval -2.34 to -0.09); and grip strength, mean difference -1.67 kg (95% confidence interval -2.96 to -0.37), although the effects on triceps skinfold thickness and grip strength were heterogeneous. Dietary advice with supplements if required resulted in a significant increase in triceps skinfold thickness compared with no advice, mean difference 0.40 mm (95% confidence interval 0.10 to 0.70), although these results are from a single trial with only 29 participants. Evidence of variable quality suggests that dietary advice with or without oral nutritional supplements may improve weight, body composition and grip strength. We found no evidence of benefit of dietary advice or oral nutritional supplements given alone or in combination on survival. Studies addressing the impact of nutritional interventions on nutritional, functional and patient-centred outcomes are needed.

Plain-language summary: Forty-five studies with a total of 3186 people are included in this review in four different comparisons: dietary advice to no advice; to oral nutritional supplements; to dietary advice plus oral nutritional supplements; and to dietary advice and nutritional supplements given together compared with no additional help. Follow-up ranged from 18 days to 24 months. There are some significant results for change in weight, muscle bulk and strength suggesting that nutritional intervention is beneficial although for some comparisons there are big differences between the studies. The authors conclude that nutritional intervention appears to be more effective than no help at improving weight, muscle bulk and strength. More research is needed to work out the best ways to help people who are losing weight because of illness in order to improve their clinical outcomes and quality of life.