Simple Stage-Matched Advice Helps Sedentary Office Workers in Sri Lanka Eat Far Better

Office workers spend the majority of their waking hours seated, and what they eat during those hours may quietly shape their long-term health more than almost any other workplace factor. A new cluster-randomised trial conducted in the Galle District of Southern Sri Lanka suggests that a carefully tailored, theory-driven dietary programme can produce striking improvements in what sedentary employees put on their plates. The study, published in BMC Public Health, found that office workers who received an intervention matched to their psychological readiness for change were dramatically more likely to progress toward healthier eating than colleagues who received no programme at all.

The research team, led by Janaka Godevithana and Champa Jayalakshmie Wijesinghe of the University of Ruhuna, together with Millawage Supun Dilara Wijesinghe of Sri Lanka’s Health Promotion Bureau, set out to address a growing public health problem. Unhealthy diets are a key risk factor for non-communicable diseases such as diabetes, cardiovascular disease and certain cancers, and office workers, with their long sedentary hours and easy access to convenience foods, are particularly exposed. The resulting burden is both medical and economic, straining health systems and reducing productivity across working populations in low- and middle-income countries.

At the heart of the intervention lies a well-known behavioural framework: the transtheoretical model, and specifically its Stage of Change construct, sometimes called the stages of readiness. Rather than treating all participants as a uniform group, the programme classified each worker according to whether they were precontemplating change, contemplating it, preparing for it, actively changing, or maintaining new habits. The content and intensity of the advice each participant received were then tailored to that stage, a principle known as stage matching. The idea is intuitive: someone who has never considered eating more vegetables needs a different conversation from someone already trying to do so.

The trial’s design gave the question unusual rigour for a workplace nutrition study. Rather than randomising individuals, which risks contamination when colleagues share meals and conversation, the researchers randomised whole clusters, meaning entire offices or administrative units, to either the intervention or a control condition. Control clusters received no intervention during the study period. Dietary intake was measured objectively at baseline and again after three months using a 24-hour dietary recall method, supplemented by a picture guide to help participants estimate portion sizes and by computer software to convert reported foods into nutrient and food-group data. Readiness to change was assessed with a validated staging algorithm.

After three months, the results were unambiguous. Both groups showed some positive movement in their stage of change, which the authors note may reflect natural progression or the effect of simply being assessed, but the change was far stronger in the intervention group, where it reached a p-value below 0.001 compared with a more modest p-value of 0.04 among controls. More importantly, the intervention group recorded significant improvements in cereal, fruit and vegetable intake alongside a reduction in unhealthy food consumption, all at the same stringent significance threshold.

The statistical strength of the effect is what makes the trial remarkable. In regression analyses, receiving the intervention was a significant predictor of progressing in stage of change, with an odds ratio of 12.2, and an even stronger predictor of achieving a measurably healthier dietary intake, with an odds ratio of 25.3. In plain terms, participants in the intervention arm had roughly twelve times the odds of advancing in their readiness to change and about twenty-five times the odds of actually improving their diet compared with controls. For a relatively brief, low-cost workplace programme, those are unusually large effects.

The analysis also revealed who benefited most. Being a clerical worker predicted a positive change in stage of change, with an odds ratio of 1.7 at the threshold of significance, suggesting that the programme resonated particularly with staff in routine administrative roles. Meanwhile, participants who were already in the action or maintenance stages at baseline were significantly more likely to achieve improvements in dietary intake, with an odds ratio of 3.5. This pattern fits the logic of the underlying theory: people who have already begun changing have the momentum to convert readiness into measurable behaviour, while those at earlier stages may need longer or more intensive support before their diets shift.

Why should a stage-matched approach outperform generic healthy-eating campaigns? Behavioural science offers several explanations. Generic messages often fail because they mismatch the recipient’s psychological state: a person in precontemplation, who sees no problem with their diet, is likely to dismiss advice framed for someone already trying to change. Stage-matched interventions meet people where they are, using consciousness-raising for the unmotivated, decisional balance exercises for the ambivalent, and concrete planning and relapse-prevention strategies for those already acting. The Sri Lankan programme also grounded its dietary targets in the Food Based Dietary Guidelines for Sri Lankans, translating international nutritional science into culturally familiar foods and portions, which likely strengthened its acceptability in local workplaces.

The trial was conducted with careful attention to research governance. It was registered in the Sri Lanka Clinical Trial Registry under registration number SLCTR/2020/025, ethical approval came from the Ethics Review Committee of the Faculty of Medicine at the University of Ruhuna, and administrative approval was obtained from the District Secretariat and health authorities in Galle. All participating office workers gave informed written consent, and the study was carried out in accordance with the Declaration of Helsinki. Workers identified with health problems during the study were referred to the nearest healthcare facility. The authors declare no competing interests, and the study was self-funded by the corresponding author.

The findings arrive at a moment when employers and governments worldwide are searching for scalable ways to curb non-communicable diseases, which now dominate the global burden of disease. Workplace interventions are attractive because they reach adults where they already gather, require little additional infrastructure, and can be delivered repeatedly. This trial suggests that the missing ingredient in many past workplace programmes may not be money or technology but psychological tailoring: asking each employee a simple question about their readiness to change and building the message around the answer. The authors caution that their results come from a single district and a three-month follow-up, and they recommend further studies assessing the intervention’s effectiveness in a more pragmatic manner across different settings. Longer follow-up would also show whether early gains persist once the programme ends. Even so, the size of the effects, the rigour of the cluster-randomised design and the simplicity of the underlying approach make this one of the most encouraging workplace nutrition results in recent years, and a template that health ministries far beyond Sri Lanka may soon want to test in their own offices.

Subject of Research: A stage of change–based dietary intervention for sedentary office workers evaluated in a cluster-randomised trial in Southern Sri Lanka

Article Title: Transforming diet in the workplace: effectiveness of a stage of change–based dietary intervention for sedentary office workers in Southern Sri Lanka – a cluster randomised trial

Article References: Godevithana, J., Wijesinghe, C. J., & Wijesinghe, M. S. D. (2026). Transforming diet in the workplace: effectiveness of a stage of change–based dietary intervention for sedentary office workers in Southern Sri Lanka – a cluster randomised trial. BMC Public Health. https://doi.org/10.1186/s12889-026-29843-3

Image Credits: AI Generated

DOI: 10.1186/s12889-026-29843-3

Keywords: dietary intervention, healthy eating, sedentary office workers, stage of change theory, cluster-randomised controlled trial, non-communicable diseases, workplace health, nutrition, Sri Lanka, behaviour change, public health, BMC Public Health