Weight management is a public health priority for the New South Wales (NSW) coal mining industry, with approximately 80% of workers classified as overweight or obese. However, evidence for effective, industry-tailored approaches remains limited (1). Structured lifestyle interventions and meal-replacement programs have shown promise for weight management, however, their effectiveness within coal mining settings has not been well established (2). Therefore, this study aimed to compare the Healthy Weight Initiative, a meal-replacement program and standard care among New South Wales coal mine workers with obesity (body mass index ≥30 kg/m²).
In an assessor-blinded, three-arm randomised controlled trial, participants (n = 119) were allocated to the 12-session Healthy Weight Initiative covering nutrition, exercise, goal setting and behaviour change (n = 40), a 12-week meal-replacement program involving two commercially available meal-replacement shakes per day (n = 39), or standard care comprising the usual GP referral pathway and existing weight-management resources (n = 40). The primary outcome was body weight, with waist circumference, diet quality (Healthy Eating Quiz) and quality of life (WHOQOL-BREF Australian Version) examined as secondary outcomes at 12 weeks and 6 months. Outcomes were analysed using intention-to-treat mixed-effects regression models.
There was no evidence of a difference in weight change between groups over time (group-by-time interaction, p = 0.373). At 12 weeks, the estimated reduction in weight was greater for HWI than SC, although the adjusted mean difference (AMD) was not statistically significant (AMD −2.37 kg, 95% CI [−5.4, 0.6]; p = 0.120). HWI was associated with a greater reduction in waist circumference than SC (AMD −4.23 cm, 95% CI [−8.1, −0.4]; p = 0.030). The odds of an improved diet-quality score were greater for HWI than SC (OR 5.70, 95% CI [1.4, 23.7]; p = 0.017) and MR (OR 11.53, 95% CI [2.7, 49.7]; p = 0.001). Psychological quality-of-life scores also improved more with HWI than SC (AMD 10.34 points, 95% CI [4.1, 16.5]; p = 0.001) and MR (AMD 10.48 points, 95% CI [4.4, 16.5]; p < 0.001). Secondary outcome analyses were exploratory and were not adjusted for multiple comparisons.
Exploratory analyses indicated that HWI may improve waist circumference, diet quality and psychological quality of life, though body weight outcomes did not differ significantly between groups. These findings suggest that structured professional support may provide health benefits beyond weight loss for coal mine workers.