The NHS Low-Calorie Diet Digital Programme: Fidelity of behaviour change technique delivery.

Aims: NHS England commissioned independent service providers to deliver the NHS Low-Calorie Diet Programme pilot. Previous research has illustrated a drift in the fidelity of behaviour change techniques (BCTs) during the delivery of the programme provided through face-to-face group or one-to-one behavioural support. The aim of this study was to assess the delivery fidelity of the BCT content in the digital delivery of the programme.

Methods: Online, app chat and phone call support content was coded using The Behaviour Change Technique Taxonomy. BCTs delivered by each service provider (N = 2) were calculated and compared to the BCTs specified in the NHS service specification and those specified in the providers' programme plans.

Results: Between 78% and 83% of the BCTs identified in the NHS service specification were delivered by the service providers. The fidelity of BCT delivery to those specified in providers' programme plans was 60%-65% for provider A, and 82% for provider B.

Conclusions: The BCT content of the digital model used in the NHS-LCD programme adhered well to the NHS service specification and providers' plans. It surpassed what has been previously observed in face-to-face services provided through group or one-on-one behavioural support models.