APROXIMACIÓN PROTEOMICA

This suite of experiments developed and evaluated an appearance-based intervention, which aimed to promote fruit and vegetable consumption in a student population. We first empirically quantified the impact of fruit and vegetable consumption on skin colour. In line with Stephen et al. (2011), high fruit and vegetable consumers exhibited significantly yellower skin than individuals who consumed 5.5 fewer portions per day on average. Furthermore, when given the opportunity to manipulate own face colour to optimise the appearance of health, individuals in the appearance-based intervention condition chose to significantly increase this colouration. Such a result is critical to the efficacy of an appearance- based intervention based on this effect as, for effective goal formation, the participant themselves should desire the illustrated skin colour changes.

Accordingly, a significant effect of intervention group, favouring the appearance-based condition, was seen on fruit and vegetable consumption over the course of the study. Participants receiving no intervention reduced their fruit and vegetable consumption over the six-week period. This may be due to the study being carried out towards the end of the academic year, which imposes financial constraints, due to the exhaustion of support funds. This period also is associated with increased anxiety due to examinations. Both of these issues may cause participants to sacrifice a healthy diet for one that is cheap, quick to prepare and high

participants commented that the exam period had negatively affected their diet, e.g., “Towards the end of the study I entered the exam period at school and attended less to maintaining a healthy diet”; “Increased workload. So less time/inclination to prepare healthy food.”; “Exams - fast food”.

Participants receiving only NHS dietary advice tended to report a similar decline in fruit and vegetable intake; consumption in this group was not significantly greater than that of the control group at any session. This supports the conclusions of Chapter 2 that the information-provision approach of current healthy-eating campaigns is insufficient to effectively motivate increased fruit and vegetable consumption.

The addition of the appearance-based intervention protected against the seasonal decline observed in control and information-only participants. This group may also be subject to financial limitations, indeed one participant in this group wrote at debrief “[my] diet did not change much mostly due to money restrictions, but the appearance benefits have made me want to eat more fruit and veg once I can afford them”. Further, restricting analysis to participants reporting childhood household income in the upper three quartiles tentatively suggests that the appearance-based intervention may be capable of motivating increased fruit and vegetable consumption in these individuals. These results warrant further investigation, but indicate that any attempt at persuading individuals to improve their diet will critically depend on general and seasonal factors affecting financial status and stresses to lifestyle.

The declining fruit and vegetable consumption in the control and information- only groups may have an additional or alternative explanation. Participants may have

overestimated fruit and vegetable intake at first report, and subsequently self- adjusted their report of diet in further sessions, potentially serving to be more accurate as attention is drawn to their diet (Golembiewski, Billingsley, & Yeager, 1976). If so, this would indicate that the control and information groups had more consistent fruit and vegetable consumption than their self-report conveys, and that the appearance-based intervention produced a larger increase in fruit and vegetable consumption than immediately obvious. To circumvent this potential confound in future study, all interventions could be administered following a period in which participants are given diet questionnaires, thereby providing the opportunity to self- adjust reported dietary intake.

In terms of theSelf-Regulation Model of Health Behavior(Carver & Scheier, 1990), these results suggest that the appearance-based intervention was sufficient to establish a motivational goal, and that participants strived to reduce the discrepancy between their current state and this goal. To increase the efficacy of this intervention technique, participants may be instructed to form plans of specifically when, where and how they aim to consume fruit and vegetables. Such implementation intentions are regarded as being important in promoting health behaviour due to their ability to act as a mnemonic device (Sheeran & Orbell, 1999), which reminds the individual of their goals or intentions in situations where the opportunity arises to achieve them. This suggests that implementation intentions are most effective when the individual is sufficiently motivated to change the behaviour of interest. The current study presents a novel means of motivating individuals to consume more fruit and vegetables, and thus may be a valuable addition to interventions which utilise

Whilst these results are encouraging, it is necessary to address a number of limitations before such an intervention can be utilised at a population level. As fruit and vegetable consumption was recorded via self-report, and participants were not blinded to intervention condition, we cannot be confident that this measure was immune to demand characteristics or overestimation. An objective estimate of dietary intake is required to eliminate this potential source of biased or selective reporting, for example, measurement of blood plasma carotenoids may be used as a biomarker of fruit and vegetable consumption (Dauchet et al., 2008).

It is chiefly important to determine whether appearance-based intervention can motivate increases in fruit and vegetable consumption amongst individuals with a more stable diet, to examine this, future studies should investigate dietary intake of a non-student population. It is also important to determine whether the technique can motivate long-term dietary changes, as sustained change is required for lasting good health. In the current study, our method of stimulus collection and calibration limited sample size and recruitment. Our encouraging results may now justify investment in automating the stimulus creation and colour calibration required for accurate appearance-based demonstration, permitting investigation in a larger, stringently randomised sample. We envisage that application of the knowledge acquired in this proof-of-concept study will serve to bolster the efficacy of this technique, potentially indicating suitability for wider-scale dietary intervention.

7. You Are What You Eat: Within-Subject Increases