Insulin resistance precedes weight loss in adults without diabetes - The Rancho Bernardo study

Insulin resistance is closely associated with both aging and overweight; ye t in old age, weight loss is common, although insulin resistance increases. To study this paradox, the authors evaluated the role of insulin resistanc e in weight change among older adults from the Rancho Bernardo Study cohort . Participants were 725 nondiabetic men and women who were aged 50-89 years when weight and insulin were measured at baseline (1984-1987). The partici pants were evaluated again in 1992-1996, at which time weight was remeasure d. Pasting insulin and homeostasis model assessment (HOMA) measurements wer e evaluated in separate but parallel statistical models as surrogates for i nsulin resistance. Insulin resistance, when defined as the top quartile of fasting insulin level or HOMA value, was significantly associated with weig ht loss before and after adjustment for baseline weight and age (fasting in sulin: beta = -1.30 kg, p = 0.01; HOMA: beta = -1.18 kg, p = 0.01). Results were the same for men versus women, for the overweight (body mass index (w eight (kg)/height (m)(2)) less than or equal to 26.6) versus the normal wei ght (body mass index > 26.6), and for younger persons (age < 70 years) vers us older persons (age greater than or equal to 70 years). Insulin-resistant individuals had a threefold increased likelihood of losing 10 or more kg c ompared with those without insulin resistance. The authors conclude that hy perinsulinemia, independently of age and baseline weight, may have a catabo lic effect in the elderly.