Single-Arm Prospective Pilot of a 5:2 Intermittent Fasting Regimen Supported by Meal Replacement and Digital Coaching in Adults with Obesity.

BACKGROUND The 5:2 intermittent fasting (IF) regimen (five days normal diet, two days energy restriction) has gained attention for obesity management due to flexibility, but traditional approaches face poor adherence and muscle loss risks. This pilot integrates energy-restricted, fiber/whey protein-rich meal replacements with digital support to enhance adherence, weight loss, and muscle preservation.

OBJECTIVE To evaluate meal replacement and digital support-enhanced 5:2 IF effects on anthropometrics, body composition, and metabolism in obese adults, assessing adherence and feasibility in a single-arm design.

METHODS This single-arm prospective pilot study recruited 20 obese adults (14 females, 6 males; body mass index (BMI) ≥28 kg/m2; age 37.0±6.3 years) for 4 weeks of 5:2 IF (two non-consecutive meal replacement days, ∼600 kcal/day). Adherence was supported by a digital platform (daily weight/diet/exercise check-ins, social messaging group management via WeChat, and weekly one-on-one guidance), with 4-week post-intervention follow-up. Assessments at baseline (weeks 2, 4, and 8) included anthropometrics-weight, BMI, and waist circumference (WC); muscle function-upper arm muscle circumference (UAMC) and handgrip strength; body composition-fat mass and skeletal muscle index (SMI); and metabolic indices-resting energy expenditure (REE) and respiratory quotient (RQ), etc. Data were analyzed using linear mixed models in SPSS 26.0, considering time effects and gender/age covariates.

RESULTS Adherence high (90% intervention, 85% follow-up). Versus baseline, 4 weeks: weight -4.0 kg (P<0.001), WC -2.8 cm (P=0.004); BF -1.8 kg (45% weight loss, P=0.001), visceral fat area trend -5.7 cm2 (P=0.131); REE -189 kcal/day (P=0.001), RQ -0.022 (P=0.018); grip unchanged (P>0.05). At 8 weeks: further reductions (P≤0.01), BF 67% weight loss; gender/age nonsignificant (P>0.05).

CONCLUSION Preliminary findings show 5:2 IF with meal replacement/digital support yields fat-predominant weight loss (67% fat) with <2% SMI decline and stable grip over 8 weeks, suggesting outpatient feasibility but needing larger RCTs/long-term validation.