Weight gain prevention during the Christmas holiday period: exploring effectiveness and participant experiences of a behavioural intervention

Weight is increasing in the population and holidays, such as Christmas, have been identified as high-risk periods. This thesis presents the development of a behavioural intervention to prevent weight gain over the Christmas period, its evaluation in a Randomised Controlled Trial (The Winter Weight Watch study), and an exploration of participant experiences of the intervention. The possible mechanisms of action of the intervention are also explored. The intervention consisted of encouragement to regularly self-weigh and record weight, physical activity calorie equivalent (PACE) information about commonly consumed festive foods and drinks and weight management tips. The hypothesised main mechanism of action was that each component would promote restraint of energy intake, preventing weight gain over Christmas. The RCT showed the intervention to be effective in preventing weight gain. At follow up the difference in weight between intervention and control groups (adjusting for baseline weight) was -0.49kg. Conscious energy restraint scores increased in the intervention group. The qualitative study showed that participants found the concept of weight gain prevention at Christmas acceptable. Self-weighing and PACE information were key drivers in encouraging restraint of energy intake. PACE information mainly prompted participants to restrain energy intake rather than increase physical activity. In conclusion, the developed intervention prevented weight gain during the Christmas period and was acceptable to participants. PACE information and self-weighing were found to be key drivers of self-regulatory behaviours. These findings hold promise for preventing weight gain during high risk periods