Protocol: The effects of nutrient- vs food- vs food-substitution-based dietary recommendations for reducing free sugar intakes, on free sugar intakes, dietary profiles and sweet taste outcomes: A randomised controlled trial.

Background: Dietary guidelines are intended to inform and aid the general public, with the aim of improving healthy diets and reducing health risk. The effectiveness of these guidelines, however, is rarely investigated.

Aim: This work investigates the effects of three different types of dietary recommendations for reducing free sugars, on free sugar intakes over 12 weeks. Secondary aims will also investigate how these different recommendations affect secondary outcomes, outcomes in subsets of the trial population, and identify barriers and facilitators to dietary change.

Methods: Using a randomised controlled parallel-group trial with three intervention and one control arms, 240 individuals consuming >5% total energy intake from free sugars will be randomized to receive: nutrient-based, nutrient- and food-based, nutrient-, food- and food-substitution-based recommendations or no recommendations, with outcomes assessed for the following 12 weeks. Our primary outcomes are free sugar intakes and adherence to the recommendations. Secondary outcomes are daily energy intake, dietary composition, anthropometry, sweet food perceptions and preferences, sweet food choice, attitudes towards sweet foods, eating behaviour and food choice, knowledge and lifestyle variables, quality of life, adverse events, and barriers and facilitators towards intervention adherence.

Results: Data will contribute to three distinct analyses: 1) Analyses to investigate the effects of the three different dietary recommendations versus control; 2) Analyses of the effects of the dietary recommendations in different population subgroups, and 3) Investigation of the barriers and facilitators to success.

Conclusion: This work offers new perspectives on the effects of different dietary recommendations to enact behaviour change.