Morbidly Obese Individuals With Impaired Fasting Glucose Have a Specific Pattern of Insulin Secretion and Sensitivity: Effect of Weight Loss After Bariatric Surgery

Obes Surg. 2006 Sep;16(9):1179-88. doi: 10.1381/096089206778392383.


Background: Obesity is often associated with hyper-secrection of insulin. Impaired fasting glucose (IFG) has recently been redefined as a fasting plasma glucose of 5.6-6.9 mmol/L. The aim of this study was to determine whether changes in insulin secretion in morbidly obese persons also commence with normal serum glucose levels.

Methods: 32 morbidly obese subjects were studied before and after bariatric surgery. Measurements were made of glucose tolerance (K(G)), insulin sensitivity (SI), first-phase insulin release and the disposition index (DI) from a frequently sampled intravenous glucose tolerance test.

Result: In morbidly obese subjects, the SI (P<0.01), DI (P<0.01) and first-phase insulin release (P<0.02) started changing with serum glucose levels considered to be normal (5.00-5.28 mmol/L). K(G) showed a clear slope according to the baseline glycemia status (P<0.05), and it was significantly related with the DI, both before (r=0.76, P<0.001) and after (r=0.57, P=0.002) surgery. Following surgery, all the variables significantly associated with insulin secretion and insulin sensitivity recovered significantly. The most significant changes occurred in morbidly obese individuals with IFG.

Conclusions: Morbidly obese subjects show slopes of insulin sensitivity and insulin secretion in accordance with their baseline serum glucose levels. The fall in first-phase insulin release begins when serum glucose values are considered normal. Morbidly obese persons with the IFG phenotype have a specific pattern of insulin sensitivity and insulin secretion. K(G) clearly discriminates the clinical phenotypes, depending on baseline serum glucose levels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Bariatric Surgery
  • Blood Glucose / metabolism*
  • Case-Control Studies
  • Fasting / physiology
  • Female
  • Follow-Up Studies
  • Glucose Intolerance / blood*
  • Glucose Intolerance / complications*
  • Glucose Intolerance / surgery
  • Glucose Tolerance Test
  • Humans
  • Insulin / blood*
  • Insulin / metabolism
  • Insulin Secretion
  • Male
  • Middle Aged
  • Obesity, Morbid / blood*
  • Obesity, Morbid / complications*
  • Obesity, Morbid / surgery
  • Weight Loss / physiology


  • Blood Glucose
  • Insulin