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Objective:
Prior study indicated pre-operative insulin levels in non-diabetic patients predict weight loss after Roux-en-Y gastric bypass (RYGB) surgery. We test this hypothesis.
Design:
Retrospective review of prospective database. Regression analyses between pre-operative insulin levels and post-operative weight loss, body mass index (BMI) change, percent excess weight loss (%EWL). Study had 80% power to detect a small effect (R2=.05).
Setting:
Surgical weight loss center for adults at large tertiary care facility.
Patients:
Consecutive sample of 141 RYGB patients between January 2005 - September 2011, no evidence of diabetes, and pre-operative insulin data with at least one year follow-up data.
Interventions:
none
Main Outcome Measures:
Pre-operative insulin levels, post-operative weight loss, BMI change, %EWL.
Results:
94/141 (68%) patients hyperinsulinemic. Mean pre-operative insulin = 39 mg/dL (range 17.2 - 276); mean BMI = 50.1 kg/m2 (range 34 - 83). 47/141 patients had normal pre-operative insulin levels. Mean insulin = 12 mg/dL (range 3.1 - 17); mean BMI = 47.6 kg/m2 (range 33-62). The groups did not differ on pre-operative BMI (p=0.104).
Regression analyses showed no significant relationships between pre-operative insulin levels and outcome variables. In non-diabetic hyperinsulinemic patients, pre-operative insulin did not predict one-year weight loss (R2=.003), BMI decrease (R2=.0002), or %EWL (R2=.003). In normoinsulinemic patients, pre-operative insulin also did not predict one-year weight loss (R2=.029), BMI decrease (R2=.017), or %EWL (R2=.007).
Conclusions:
Pre-operative insulin levels in non-diabetic hyperinsulinemic patients were not predictive of post-surgery weight loss, BMI change or %EWL, which do not confirm findings from a prior study. Further investigation is needed to confirm whether a relationship exists as bariatric surgery evolves into the primary treatment of metabolic disease in the morbidly obese patient.