Most people try to eat healthy, but the temptation of unhealthy foods (among other factors) can make it difficult. Despite these difficulties, some people still achieve their healthy eating goals. Following self-determination theory (SDT; Ryan & Deci, 2000), we propose that relative autonomous motivation (RAM) can foster people’s effort in pursuing health goals. In two daily diary studies, we tested the hypothesis that RAM predicts attainment of healthy eating goals, especially when it is difficult. In Study 1, we focused on difficulties associated with trying to eat certain foods while avoiding others, whereas in Study 2, we focused on difficulties associated with the availability of unhealthy and healthy foods. Multilevel analyses provided some support our hypothesis, and highlighted the role of RAM for eating (vs. skipping) lunch and packing a lunch–two approach-based healthy eating strategies. We discuss these findings in relation to SDT and propose directions for future research on within-person changes in motivation and other sources of difficulty.

大多数人都试图吃得健康，但不健康食物的诱惑（以及其他因素）可能会让它变得困难。尽管有这些困难，一些人仍然实现了他们的健康饮食目标。根据自我决定理论 (SDT; Ryan & Deci, 2000)，我们提出相对自主动机 (RAM) 可以促进人们追求健康目标的努力。在两项日常日记研究中，我们检验了 RAM 预测实现健康饮食目标的假设，尤其是在困难时。在研究 1 中，我们关注与尝试吃某些食物同时避免其他食物相关的困难，而在研究 2 中，我们关注与获取不健康和健康食物相关的困难。多层次分析为我们的假设提供了一些支持，并强调了 RAM 在饮食中的作用（对比。跳过）午餐和打包午餐——两种基于方法的健康饮食策略。我们讨论了与 SDT 相关的这些发现，并为未来关于个人动机变化和其他困难来源的研究提出了方向。