Exploring Adherence and Acceptability of an Intermittent Carbohydrate Restriction Regime (ICARB) in Free-Living Adults: A Feasibility Study.

The ICARB protocol achieved strong adherence, with 24 of 28 participants meeting the ≤50 g/day carbohydrate target on low-carbohydrate days at both weeks 1 and 4.

• 37 participants were enrolled, with 34 completing the study (16 male; mean age 22.3 ± 5.4 years; 10 with BMI ≥ 25 kg/m²)
• Mean carbohydrate reduction was 128.7 ± 90.4 g/day in Week 1 compared with non-restricted days (p < 0.0001)
• Mean carbohydrate reduction was 136.9 ± 101.8 g/day in Week 4 compared with non-restricted days (p < 0.0001)
• The protocol required limiting carbohydrate intake to ≤50 g on two non-consecutive days per week while maintaining unrestricted intake on remaining days

Participants who were overweight showed significant reductions in body weight and fat mass over the 4-week ICARB protocol.

• Body weight reduction in overweight participants was -1.1 ± 1.4 kg (p = 0.04)
• Fat mass reduction in overweight participants was -0.95 ± 1.0 kg (p = 0.02)
• No group-level changes in body weight or fat mass were observed across all participants
• The study did not prescribe energy restriction on any days

Most participants expressed willingness to maintain the ICARB diet beyond the study period, with suggested durations ranging from an additional 2 weeks to indefinitely.

• Participant perceptions were evaluated through qualitative exit interviews
• Perceived benefits included improved dietary awareness, energy, and mood
• Challenges included identifying foods that met the carbohydrate criteria, navigating social eating occasions, and limited food choices when dining out
• Participants described adaptation strategies including meal planning and forming consistent routines

The study was designed as a feasibility study evaluating a 4-week ICARB protocol in free-living adults without prescribed energy restriction.

• Healthy adults aged 19–65 years with a BMI of 19–39 kg/m² were recruited
• Participants were required to be weight-stable, not following a restrictive diet, and free from diagnosed medical conditions
• Exclusion criteria included high physical activity (>3 sessions/week), use of weight-altering medications, pregnancy or breastfeeding, and indicators of disordered eating or poor sleep quality
• Outcome measures included dietary intake, body weight, adiposity, resting energy expenditure (REE), and fasted respiratory quotient (RQ)

The ICARB protocol was found to be feasible and acceptable over 4 weeks under free-living conditions, supporting its short-term practicality.

• 34 of 37 enrolled participants completed the study, indicating a low dropout rate
• Both quantitative outcomes and qualitative exit interviews were used to assess feasibility and acceptability
• The authors conclude that findings 'warrant longer-term and controlled studies to assess metabolic and behavioural outcomes'
• The study is registered at ClinicalTrials.gov (NCT07056465)