Determinants of Fasting in Patients with Cancer : A Longitudinal Study Using an Integrated Behavior Change Model

Abstract

Fasting is currently not recommended during cancer treatment. Despite this, a meaningful proportion of patients with cancer have positive perceptions of fasting, or practice fasting during their treatment. The integrated behavior change model (IBCM) combines variables and hypotheses derived from the theory of planned behavior, the self-determination theory, and the health action process approach to explain health behavior. Based on the IBCM, the present study examined determinants of fasting in patients with cancer. A total of 114 patients (M = 52 years, 108 women) completed an online questionnaire measuring past behavior, action planning, intention, attitudes, subjective norm, perceived behavioral control (PBC), autonomous motivation, controlled motivation, amotivation, and perceived autonomy support at an initial time point and informed one month later to what extent they had performed fasting in the last 30 days. Hypotheses were tested using a Bayesian path analysis. The model tested confirmed most of the hypothesized paths of the IBCM. Autonomous motivation was significantly directly linked to intention, while attitude and subjective norm were not significantly linked to intention. PBC was significantly indirectly linked to fasting through intention and action planning. Past behavior was significantly indirectly linked to actual fasting through some variables of the IBCM, with a significant strong link between past behavior and autonomous motivation. Autonomous motivation appears to play a central role in the practice of fasting among patients with cancer. Future research should apply the IBCM to fasting among various populations and with a longer period of follow-up.