CR and Insulin Sensitivity

[Guest guest]

Hi folks:

I just noticed this relatively new paper from Fontana and Holloszy:

Effects of long-term calorie restriction and endurance exercise on glucose

tolerance, insulin action, and adipokine production.

Fontana L, Klein S, Holloszy JO.

Division of Geriatrics and Nutritional Science and Center for Human Nutrition,

Washington University School of Medicine, Campus Box 8113, 4566, Avenue,

St. Louis, MO, 63110, USA, lfontana@....

Calorie restriction (CR) slows aging and is thought to improve insulin

sensitivity in laboratory animals. In contrast, decreased insulin signaling

and/or mild insulin resistance paradoxically extends maximal lifespan in various

genetic animal models of longevity. Nothing is known regarding the long-term

effects of CR on glucose tolerance and insulin action in lean healthy humans.

n this study we evaluated body composition, glucose, and insulin responses to an

oral glucose tolerance test and serum adipokines levels in 28 volunteers, who

had been eating a CR diet for an average of 6.9 +/- 5.5 years, (mean age 53.0

+/- 11 years), in 28 age-, sex-, and body fat-matched endurance runners (EX),

and 28 age- and sex-matched sedentary controls eating Western diets (WD).

We found that the CR and EX volunteers were significantly leaner than the WD

volunteers. Insulin sensitivity, determined according to the HOMA-IR and the

Matsuda and DeFronzo insulin sensitivity indexes, was significantly higher in

the CR and EX groups than in the WD group (P = 0.001). Nonetheless, despite high

serum adiponectin and low inflammation, approximately 40% of CR individuals

exhibited an exaggerated hyperglycemic response to a glucose load. This impaired

glucose tolerance is associated with lower circulating levels of IGF-1, total

testosterone, and triiodothyronine, which are typical adaptations to

life-extending CR in rodents.

PMID: 19904628

Not sure what it might mean for us, however.

Rodney.