Interaction Between Dietary Lipids and Physical Inactivity on Insulin Sensitivity and on Intramyocellular Lipids in Healthy Men

Abstract

OBJECTIVE—To assess the effect of a possible interaction between dietary fat and physical inactivity on whole-body insulin sensitivity and intramyocellular lipids (IMCLs).

RESEARCH DESIGN AND METHODS—Eight healthy male volunteers were studied on two occasions. After 2 days of an equilibrated diet and moderate physical activity, participants remained inactive (bed rest) for 60 h and consumed either a high–saturated fat (45% fat, of which ∼60% was saturated fat [BR-HF]) or a high-carbohydrate (70% carbohydrate [BR-HCHO]) diet. To evaluate the effect of a high-fat diet alone, six of the eight volunteers were restudied after a 2-day equilibrated diet followed by 60 h on a high–saturated fat diet and controlled physical activity (PA-HF). Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp and IMCL concentrations by ¹H-magnetic resonance spectroscopy.

RESULTS—Insulin-mediated glucose disposal was decreased by BR-HF condition (−24 ± 6%, P < 0.05) but did not change with BR-HCHO (+19 ± 10%, NS). BR-HF and BR-HCHO increased IMCL levels (+32 ± 7%, P < 0.05 and +17 ± 8%, P < 0.0011, respectively). Although the increase in IMCL levels with PA-HF (+31 ± 19%, P = 0.12) was similar to that during BR-HF, insulin-mediated glucose disposal (−7 ± 9%, NS) was not decreased.

CONCLUSIONS—These data indicate that physical inactivity and a high–saturated fat diet may interact to reduce whole-body insulin sensitivity. IMCL content was influenced by dietary lipid and physical inactivity but was not directly associated with insulin resistance.