A Behavior Change Technique-Based Text Messaging Intervention for Obesity Among Employed Adult Men Younger Than 40 Years: Pilot Randomized Controlled Trial.

Background: In Japan, employed men younger than 40 years are not eligible for specific health guidance, and evidence regarding obesity interventions targeting this population is limited. Furthermore, due to the shortage of human resources in occupational health settings, a need has arisen for simple and implementable support methods. Support via SMS text message is expected to be a low-cost and scalable method for health guidance; however, its effectiveness in this target population has not been sufficiently evaluated. Objective: This pilot randomized controlled trial aimed to assessed the feasibility, acceptability, and preliminary effectiveness of an SMS text messaging intervention among employed men younger than 40 years with obesity (BMI ≥25 kg/m²). Methods: An unblinded randomized controlled trial was conducted with 35 participants (intervention group, n=17; control group, n=18). The intervention group received one-way SMS text messaging based on behavior change techniques targeting diet and physical activity, delivered 3 times per week for 12 weeks (36 messages total). The control group received a pamphlet and a self-monitoring record sheet at baseline. The primary outcome was the proportion achieving ≥3% weight loss. Secondary outcomes included BMI, waist circumference, and psychological and behavioral measures. Feasibility and acceptability were also assessed. Results: The proportion achieving ≥3% weight loss was 23.5% (4/17) in the intervention group and 5.6% (1/18) in the control group ( Conclusions: The findings support the feasibility and acceptability of an SMS text messaging intervention for health guidance among employed men younger than 40 years with obesity, although evidence of its effectiveness remains preliminary. Further research with larger samples is needed to evaluate its effectiveness and optimize the intervention.