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The role of whey protein supplementation after one-anastomosis gastric bypass: Results of a double-blind randomized controlled trial.

  • 2025-10
  • Clinical nutrition ESPEN 69
    • Keivan Sabooni
    • Farnaz Farsi
    • Shiva Safari
    • Mohammad Mahjoubi
    • Amir Hossein Davarpanah Jazi
    • Delaram Moosavi
    • Zahra Gholi
    • Mohammad Kermansaravi
    • Shahab Shahabi

Study Design

Type
Randomized Controlled Trial (RCT)
Population
Seventy-eight participants (BMI 40-50 kg/m^2) undergoing primary OAGB
Methods
Double-blind RCT, daily pure whey protein (2 × 15 g scoops; ~22.6 g protein/day) or visually identical placebo for three months; anthropometric measurements, bioelectrical impedance analysis, and laboratory assessments at baseline, 1 and 3 months postoperatively
Blinding
Double-blind
Duration
three months
Funding
Unclear

Background

Metabolic and bariatric surgery (MBS) is an effective intervention for morbid obesity. Yet, rapid weight loss often indicates the early postoperative period, which can include substantial reductions in lean body mass. One Anastomosis Gastric Bypass (OAGB) is being used more frequently; however, data on the postoperative effects of whey protein supplementation in this specific procedure are still limited.

Objective

This double-blind, randomized controlled trial (RCT) aimed to investigate the effects of whey protein supplementation on weight loss, body composition, and nutritional markers in patients undergoing OAGB.

Methods

Seventy-eight participants (BMI 40-50 kg/m2) undergoing primary OAGB were randomized to receive either daily pure whey protein (2 × 15 g scoops; ∼22.6 g protein/day) or a visually identical placebo for three months. Anthropometric measurements, bioelectrical impedance analysis (body composition), and laboratory assessments were performed at baseline (preoperative) and 1 and 3 months postoperatively. Standard multivitamins and mineral supplementation were provided to all participants. Adherence was monitored through diaries and regular follow-up calls.

Results

Both groups demonstrated significant weight loss and improved fasting blood glucose, HbA1C, and lipid profiles three months post-surgery. No significant differences between groups emerged in total weight loss percentage or key nutritional markers (e.g., albumin). However, the whey protein group exhibited significantly lower reductions in fat-free mass, muscle mass, and total body water compared to the placebo group (p < 0.05).

Conclusion

In patients undergoing OAGB, whey protein supplementation did not substantially alter total weight loss or biochemical markers within three months; however, it did help preserve lean body mass. While cost and adherence remain potential barriers, whey protein supplementation may offer a practical, tolerable option to support muscle mass retention in the early postoperative period.

Registration

This research was registered (30-04-2024) in the https://irct.behdasht.gov.ir with registration number: IRCT20240209060949N1.

Research Insights

  • Whey Protein→Preserved Muscle Mass

    the whey protein group exhibited significantly lower reductions in fat-free mass, muscle mass, and total body water compared to the placebo group (p < 0.05).

    Effect
    Beneficial
    Effect size
    Moderate
    Dose
    2 × 15 g scoops; ~22.6 g protein/day
  • Whey Protein→Reduced Lean Body Mass Loss

    the whey protein group exhibited significantly lower reductions in fat-free mass, muscle mass, and total body water compared to the placebo group (p < 0.05).

    Effect
    Beneficial
    Effect size
    Moderate
    Dose
    2 × 15 g scoops; ~22.6 g protein/day
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