Methenitis Spyridon, Nomikos Tzortzis, Kontou Eleni, Kiourelli Kleio-Maria, Papadimas George, Papadopoulos Constantinos, Terzis Gerasimos
Sports Performance Laboratory, School of Physical Education & Sports Science, National and Kapodistrian University of Athens, Greece.
Department of Nutrition and Dietetics, School of Health Sciences & Education, Harokopio University, Greece.
Nutr Metab Cardiovasc Dis. 2023 Apr;33(4):817-825. doi: 10.1016/j.numecd.2022.12.027. Epub 2023 Jan 5.
The aim of this study was to investigate the hypothesis that healthy, normal-weight females with greater proportions and sizes of the oxidative muscle fibers would also be characterized by a healthier body composition compared with individuals with increased glycolytic fibers, even if both follow similar nutritional plans.
Vastus lateralis muscle fiber-type composition, body composition through dual-energy X-ray absorptiometry, and dietary intakes through questionnaire were evaluated in twenty-two young, healthy, non-obese females (age: 21.3±1.8yrs, body mass: 67.5±6.2 kg, body height: 1.66±0.05m, body mass index (BMI): 24.2±2.6 kg m). The participants were allocated into two groups according to their type I muscle fibers percentage [high (HI) and low (LI)]. The participants of the LI group were characterized by significantly higher body mass, fat mass, BMI, and cross-sectional and percentage cross-sectional area (%CSA) of type IIx muscle fibers compared with participants of the HI group (p < 0.021). In contrast, the HI group was characterized by higher cross-sectional and %CSA of type I muscle fibers compared with the LI group (p < 0.038). Significant correlations were observed between body fat mass, lean body mass, total energy intake, fat energy intake, and %CSAs of type I and IIx muscle fibers (r: -0.505 to 0.685; p < 0.05).
In conclusion, this study suggests that muscle fiber composition is an important factor that at least partly could explain the observed differential inter-individual responses of the body composition to nutrition in female individuals. Increased %CSAs of type I muscle fibers seem to act as a protective mechanism against obesity and favor a healthier body composition, neutralizing the negative effect of increased caloric fats intake on body composition, probably because of their greater oxidative metabolic properties and fat utilization capacities. In contrast, female individuals with low type I and high type IIx %CSAs of type I seem to be more metabolically inflexible and dietinduced obesity prone, even if they consume fewer total daily calories and fats.
本研究旨在探讨这一假设，即健康、体重正常的女性若具有更大比例和尺寸的氧化型肌纤维，即便她们与具有更多糖酵解型纤维的个体遵循相似的营养计划，其身体成分也会更健康。
对22名年轻、健康、非肥胖女性（年龄：21.3±1.8岁，体重：67.5±6.2千克，身高：1.66±0.05米，体重指数（BMI）：24.2±2.6千克/米²）的股外侧肌纤维类型组成、通过双能X线吸收法测定的身体成分以及通过问卷调查得出的饮食摄入量进行了评估。根据她们的I型肌纤维百分比将参与者分为两组[高（HI）组和低（LI）组]。与HI组参与者相比，LI组参与者的体重、脂肪量、BMI以及IIx型肌纤维的横截面积和横截面积百分比（%CSA）显著更高（p < 0.021）。相比之下，与LI组相比，HI组的I型肌纤维横截面积和%CSA更高（p < 0.038）。在体脂肪量、瘦体重、总能量摄入、脂肪能量摄入以及I型和IIx型肌纤维的%CSA之间观察到显著相关性（r：-0.505至0.685；p < 0.05）。
总之，本研究表明肌纤维组成是一个重要因素，至少在一定程度上可以解释女性个体身体成分对营养的不同个体间反应。I型肌纤维%CSA的增加似乎起到了预防肥胖的保护机制作用，有利于更健康的身体成分，抵消了高热量脂肪摄入对身体成分的负面影响，这可能是因为它们具有更强的氧化代谢特性和脂肪利用能力。相比之下，I型肌纤维%CSA低且IIx型肌纤维%CSA高的女性个体似乎代谢灵活性更低，更容易因饮食导致肥胖，即使她们每日摄入的总热量和脂肪量较少。
