Accepted for/Published in: JMIR Formative Research
Date Submitted: Jun 15, 2026
Date Accepted: Oct 5, 2026
A Behavior Change Technique–Based Text Messaging Intervention for Obesity Among Employed Adult Men Younger Than 40 Years: A Pilot Randomized Controlled Trial
ABSTRACT
Background:
In Japan, employed men under the age of 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 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 study aimed to examine the feasibility and preliminary efficacy of an SMS text messaging intervention designed based on behavior change techniques (BCTs) among working men under 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 BCTs targeting diet and physical activity, delivered three 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, psychological and behavioral measures, and feasibility indicators (delivery rate, cost, and acceptability).
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 (P=.177; odds ratio 5.23). Waist circumference significantly decreased in the intervention group compared to baseline (P=. 016), whereas no significant between-group differences were observed in weight, BMI, or psychological measures. The SMS delivery rate was 95.5% with a total cost of JPY 15, 264 over 12 weeks. None of the participants dropped out, and their overall acceptability was high.
Conclusions:
BCT-based SMS text messaging intervention is a feasible and low-cost approach for health guidance among working men aged <40 years. Although no significant effect was observed on the primary outcome, preliminary effects on waist circumference were identified, supporting the need for larger trials. Clinical Trial: UMIN-CTR, UMIN000054203. https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000061484
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