Insulin-sensitive Obesity: Lessons From Longitudinal Data
Condition: Insulin Sensitivity/Resistance; Obesity
MeSH terms: Obesity; Insulin Resistance
Study type: Observational

Summary: 
      People who are overweight and/or obese are at risk of insulin resistance and type 2 diabetes.
      However, research has shown that some overweight and/or obese individuals remain
      insulin-sensitive and metabolically healthy despite their unhealthy body weight.

      The investigators hypothesise that overweight and/or obese people who were deemed
      insulin-sensitive in previous studies will maintain their insulin sensitivity and metabolic
      health over time. The investigators also hypothesise that the preservation of insulin
      sensitivity will be accompanied by key metabolic health markers.
    

Detailed description: 
      While obesity is a risk factor for metabolic disease, sub cohorts with obesity not
      complicated by the metabolic syndrome have been described. These so called "metabolically
      healthy obese" may have reduced risk of type 2 diabetes, cardiovascular disease and all-cause
      mortality compared with individuals with obesity who present with components of the metabolic
      syndrome.

      Longitudinal studies with diabetes and cardiovascular disease risk endpoints reported that
      individuals with obesity who are metabolically healthy (MHO) held an intermediate health
      status, such that they were still worse off than the healthy normal-weight individuals. While
      there have been studies evaluating the stability of the MHO phenotype over time, no study has
      reported the durability of insulin-sensitivity per se, as measured by the gold-standard
      hyperinsulinaemic-euglycaemic clamp. In the present study, we aimed to trace the change in
      insulin resistance/sensitivity, and to uncover predictors of insulin resistance in older age.
      The secondary aims were to trace the change in body composition, fat distribution and
      metabolic markers over time in a well-phenotyped cohort studied approximately 5-6 years
      apart.
    

Observational model: Cohort
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Participants of two previous separate studies performed at the Garvan Institute of Medical
        Research (Sydney, Australia) were contacted by postal mail to gauge interest in
        participating in this follow-up study. In the original studies, exclusion criteria included
        weight change greater than 2 kg in the preceding 6 months, self-reported regular exercise
        for periods longer than 60 min/week, treatment with medications known to affect insulin
        sensitivity or carbohydrate metabolism, known renal, cardiac, or liver disease and current
        cancer, planning pregnancy, consumption of more than 20 and 40 g/day alcohol for women and
        men, respectively, and smoking >10 cigarettes/day
      
Biospecimen description: 
      Serum, plasma, subcutaneous abdominal fat, skeletal muscle
    
Keywords: Hyperinsulinaemic-euglycaemic clamp; Body fat composition; Dual-energy x-ray absorptiometry; Obesity; Insulin resistance