Physical inactivity and obesity underlie the insulin resistance of aging.
Level 4 - case-series / case-control
Cross-sectional physiological comparative study
PubMed 19401446 · doi:10.2337/dc09-0267
What was done
Researchers measured insulin sensitivity via a glucose clamp across six subgroups totaling 70 participants: younger endurance-trained athletes (n = 7), older athletes (n = 12), younger normal-weight sedentary subjects (n = 11), older normal-weight sedentary subjects (n = 10), younger obese sedentary subjects (n = 15), and older obese sedentary subjects (n = 15).
What was found
The abstract reports no numeric values, effect sizes, or p-values. Directionally, insulin sensitivity was not different between younger and older participants within matched activity and weight categories (younger vs. older athletes, younger vs. older normal-weight subjects, or younger vs. older obese subjects). Across all ages, athletes were more insulin sensitive than normal-weight sedentary individuals, who were more insulin sensitive than obese individuals.
Why it matters
It suggests that the insulin resistance commonly attributed to biological aging is instead driven by lifestyle factors, specifically chronic physical inactivity and adiposity.
Limits
The abstract provides no quantitative metrics or variance estimates. The sample sizes within subgroups were very small (7 to 15 subjects per group). The cross-sectional design cannot establish causality or follow longitudinal changes over time.
Cited by
- contradicts Aging is the primary cause of decreased insulin sensitivity, surpassing obesity and genetics.