Dietary Intentions and Eating Behaviour: Factors Shaping Dietary Choices

While many people may know what a healthy diet should look like, putting healthier dietary choices into practice is often the real challenge that goes beyond a simple lack of willpower. Established habits can play an important role, and with eating in particular, food-related choices and behaviours occur repeatedly throughout the day and take place within changing environments, routines and circumstances. The difference between what we intend to do and what we ultimately do is often referred to as the intention–behaviour gap. It is particularly relevant to nutrition because eating is not a single decision, and while nutrition knowledge and motivation matter, they are only part of the picture. Existing habits, perceived control, stress and the ability to translate intentions into specific actions can all influence dietary behaviour.

This article explores potential factors that influence whether healthy eating intentions become actual eating behaviours.

What does the evidence say?

Intentions matter, but they do not fully predict what we eat

• A 2011 meta-analysis of 237 prospective tests of the Theory of Planned Behaviour found that intentions predicted future health behaviour, but they did not fully explain what people actually did. For dietary behaviours specifically, the model explained 50.3% of the variance in dietary intentions but only 21.2% of actual dietary behaviour. Intention and perceived behavioural control were important predictors of dietary behaviour, while past behaviour also contributed to predicting future behaviour. These findings are consistent with the intention–behaviour gap in nutrition: people may genuinely intend to make healthier food choices, yet these factors explain only part of what they ultimately eat. (1)

Nutrition knowledge is useful, but knowledge alone appears insufficient

• A systematic review from 2014 examined 29 studies investigating whether nutrition knowledge translates into healthier eating. Around two-thirds of the studies (65.5%) found that greater nutrition knowledge was associated with healthier dietary choices, particularly higher fruit and vegetable intake and lower fat intake. However, these associations were generally weak, and 10 studies found no significant relationship at all. Overall, the review suggests that nutrition knowledge can contribute to healthier eating, but knowledge by itself does not consistently translate into healthier dietary behaviour. The authors also noted that practical skills, motivation, food availability, cost and convenience may affect whether people are able to put what they know into practice. (2)

Existing habits can influence behaviour alongside conscious intentions

• A prospective study followed 239 adults to examine how unhealthy snacking habits and intentions to avoid snacks predicted subsequent intake. Stronger habits were associated with greater unhealthy snack consumption, while stronger intentions to avoid snacking were associated with lower intake. However, the researchers found no evidence that strong habits weakened the influence of intention. This suggests that habits and intentions may both matter for eating behaviour, rather than habits always overriding conscious intentions. (3)

Stress can shift the foods we choose

• A systematic review and meta-analysis from 2022 combined 54 studies involving nearly 120,000 healthy adults to investigate how stress influences eating behaviour. Stress was associated with a small increase in overall food intake and unhealthy food consumption, alongside a small decrease in healthy food consumption. However, the effects were modest and varied considerably between studies, suggesting that people do not respond to stress in the same way. Some may eat more, others less, while others show little change. Overall, the findings suggest that stress is associated with changes in eating patterns and may shift food choices towards less healthy options, rather than simply causing everyone to overeat. (4)

Turning an intention into a specific plan may help

• A 2026 systematic review and meta-analysis of 12 randomised comparisons involving 2,399 adults found that if–then planning led to a small increase in fruit and vegetable intake. Participants who linked a specific situation with a specific response reported eating around 0.29 additional portions per day compared with active control groups. While the effect was small and all studies relied on self-reported intake, the findings suggest that translating a general intention into a concrete situation–action plan may modestly increase fruit and vegetable intake. (5)

What does that mean in practice?

• Healthy eating intentions appear to be an important predictor of dietary behaviour, but they only explain part of what people ultimately eat. Factors such as perceived control, previous behaviour and everyday circumstances can influence whether an intention is actually followed.

• Nutrition knowledge can contribute to healthier dietary choices, but simply knowing what constitutes a healthy diet does not necessarily result in behavioural change. Practical factors such as convenience, food availability, cost and the ability to apply nutritional knowledge may also be relevant.

• Existing habits and stress can influence dietary choices alongside conscious intentions. However, habits may not necessarily override intentions, and responses to stress vary considerably between individuals, highlighting that eating behaviour is shaped by several interacting factors rather than one single driver.

• Translating general dietary intentions into specific situation-based plans may help support behaviour change. If–then planning has shown small improvements in fruit and vegetable intake, suggesting that defining a specific response to a particular situation may help turn a general dietary intention into a more concrete action.

Key takeaway

Healthy eating behaviour is not determined by knowledge, motivation or willpower alone. Intentions remain important, but habits, perceived control, stress and practical circumstances may influence whether they translate into action, while specific planning may help make intended dietary changes more likely to occur.

References:

1. McEachan RRC, Conner M, Taylor NJ, Lawton RJ. Prospective prediction of health-related behaviours with the Theory of Planned Behaviour: a meta-analysis. Health Psychology Review. 2011. doi:10.1080/17437199.2010.521684.

2. Spronk I, Kullen C, Burdon C, O'Connor H. Relationship between nutrition knowledge and dietary intake. British Journal of Nutrition. 2014;111:1713–1726. doi:10.1017/S0007114514000087.

3. Gardner B, Corbridge S, McGowan L. Do habits always override intentions? Pitting unhealthy snacking habits against snack-avoidance intentions. BMC Psychology. 2015;3:8. doi:10.1186/s40359-015-0065-4.

4. Hill D, Conner M, Clancy F, Moss R, Wilding S, Bristow M, O'Connor DB. Stress and eating behaviours in healthy adults: a systematic review and meta-analysis. Health Psychology Review. 2022;16(2):280–304. doi:10.1080/17437199.2021.1923406.

5. Melum SK, Martiny-Huenger T. A systematic review and meta-analysis on the effectiveness of if-then plans – in a strict sense – to facilitate fruit and vegetable consumption in adults. International Journal of Behavioral Nutrition and Physical Activity. 2026;23:51. doi:10.1186/s12966-026-01915-y.

Disclaimer: This article is for educational purposes only and does not replace medical advice. Individual needs vary, and personalised guidance from a qualified healthcare professional is recommended for tailored support.