Understanding the complex linkage between obesity and food choice is pivotal to establishing effective dietary guidance that resonates with consumers. The aims of this thesis were to evaluate: (1) serving size (SS) guidance schemes and their effectiveness; (2) consumer estimations of portion size (PS) and energy density (ED), and anticipated consumption guilt (ACG) for perceived 'healthier' vs. 'standard' foods; (3) consumer opinions, perceptions of efficacy and the precision of a range of portion size estimation aids (PSEA); and (4) the nutritional quality (NQ) and energy cost (EC) of own brand (OB) vs. market brand (MB) foods. A literature review and three studies were undertaken. In the first study, three pairs of isoenergy dense (kJIlOOg) foods - 'healthier' vs. 'standard' cereals, drinks and coleslaws - were selected. For each food, subjects (n186) served an appropriate PS for themselves, estimated its ED and rated their ACG. Subjects estimated larger portions of the ' healthier' (reduced fat) coleslaw than the 'standard' version, and perceived all 'healthier' foods to be lower in ED than their 'standard' alternatives, despite being isoenergy dense. Higher ACG was associated with the 'standard' foods . In the second study, a range of PSEA were evaluated using both qualitative (six focus groups, each of three to eight participants) and quantitative (practical use of PSEA; n 120) methods. Consumers indicated preference for "visual" PSEA (reference objects, household measures e.g. cup, and indicators on food packaging) for amorphous cereal products such as rice. In the third study, a basket of commonly consumed foods (n 32) were compared in terms of NQ and EC at two time points using two methods of nutritional profiling. Despite OB foods being significantly lower in EC (£/MJ) than the MB, there were no differences in the overall NQ. In conclusion, consumer understanding of PS, perceptions of ED and preferences for PSEA should be considered in future dietary guidance. OB foods should be promoted as nutritionally comparable to their more expensive MB counterparts where appropriate.