Table 2 Intervention description: Content of nutrition program (12 weeks) in the various ProMuscle interventions

Type and frequency of guidance

Short explanation on protein drinks at start of intervention by research dietitian (no consultation).

Individual consultations with dietitian; before intervention, after 6 weeks, and additional phone consultation when needed.

Individual consultations with dietitian; at the start of the intervention, in week 2 or 3, and at the end of the intervention and additional consultations when needed. One group meeting at the end (location 1).

One individual consultation with dietitian at the start, three group meetings (location 2).

Type and frequency of protein product

Provision of 250mL protein supplemented beverage containing 15 g protein. One drink directly after breakfast, one drink directly after lunch.

Provision of range of free protein-rich products, such as dairy drinks, cheese, or yoghurt. Tailored to individual needs and preferences. Protein-rich products were mainly consumed during breakfast and lunch, aimed at reaching consumption of 25g protein per main meal.

No provision of supplements or products. Advise was focused on animal-based as well as plant-based protein. Tailored to individual needs and preferences. Aimed at 20-25g protein per main meal.