Muscle fiber type is associated with obesity and weight loss.
The purpose of this study was to test the hypothesis that muscle fiber type is related to obesity. Fiber type was compared 1) in lean and obese women, 2) in Caucasian (C) and African-American (AA) women, and 3) in obese individuals who lost weight after gastric bypass surgery. When lean (body mass index 24.0 +/- 0.9 kg/m(2), n = 28) and obese (34.8 +/- 0.9 kg/m(2), n = 25) women were compared, there were significant (P < 0.05) differences in muscle fiber type. The obese women possessed fewer type I (41.5 +/- 1.8 vs. 54.6 +/- 1.8%) and more type IIb (25.1 +/- 1.5 vs. 14.4 +/- 1.5%) fibers than the lean women. When ethnicity was accounted for, the percentage of type IIb fibers in obese AA was significantly higher than in obese C (31.0 +/- 2.4% vs. 19.2 +/- 1.9%); fewer type I fibers were also found in obese AA (34.5 +/- 2.8% vs. 48.6 +/- 2.2%). These data are consistent with the higher incidence of obesity and greater weight gain reported in AA women. With weight loss intervention, there was a positive relationship (r = 0.72, P < 0.005) between the percentage of excess weight loss and the percentage of type I fibers in morbidly obese patients. These findings indicate that there is a relationship between muscle fiber type and obesity.
Tanner
Charles J
CJ
Department of Exercise and Sport Science, East Carolina University, Greenville, North Carolina 27858, USA. Tannerc@mail.ecu.edu
Barakat
Hisham A
HA
Dohm
G Lynis
GL
Pories
Walter J
WJ
MacDonald
Kenneth G
KG
Cunningham
Paul R G
PR
Swanson
Melvin S
MS
Houmard
Joseph A
JA
D000328:Adult; D044383:Black People; D015992:Body Mass Index; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D018656:Muscle Fibers, Fast-Twitch / Q000473:pathology; D018485:Muscle Fibers, Skeletal / Q000473:pathology*; D018657:Muscle Fibers, Slow-Twitch / Q000473:pathology; D009765:Obesity / Q000473:pathology* / Q000601:surgery; D009767:Obesity, Morbid / Q000473:pathology; D015431:Weight Loss; D044465:White People; D001741:Black or African American