Objective To reveal the development characteristics of fat percentage and muscle mass in three nomadic populations in the Hexi Corridor of Gansu.   Methods Bioelectrical impedance analysis was used to determine the values of 13 indexes of fat percentage and muscle mass in 263 cases of Gansu Kazakhs, 400 cases of Gansu Mongols, and 362 cases of Yugu adults.     Results In the three nomadic populations of the Hexi Corridor, visceral fat level of males was significantly positively correlated with age, while total body muscle mass and estimated bone mass were significantly negatively correlated with age. In females, percent body fat, visceral fat grade, percent left and right upper limb fat, percent right lower limb fat and percent trunk fat were all significantly positively correlated with age, while trunk muscle mass was significantly negatively correlated with age. The result  of principal component analysis showed that the three nomadic populations in the Hexi Corridor were close to each other in terms of fat percentage and muscle mass characteristics, with high visceral fat grades in males and normal visceral fat grade in females. Among the 13 populations, three nomadic groups in the Hexi Corridor had high fat percentage and muscle mass. Overall, the nomadic population had greater fat percentage and muscle mass than the semi-agricultural and semi-pastoral population, and even more significantly greater than the agrarian population. The long-term integration of the historical Hexi Corridor populations result ed in the relative proximity of the genetic structure of three nomadic populations, which was a genetic factor for the proximity of their fat percentage and muscle mass. Higher per capita disposable income was a socio-economic factor for high fat percentage and muscle mass among Gansu Kazakhs and Gansu Mongolians. Low average annual temperature was an environmental factor for high muscle mass among Gansu Kazakhs and Yugus.    Conclusion Gansu Kazakhs, Gansu Mongols, and Yugus have the fat percentage and muscle mass characteristic of northern Chinese populations.

 Fat percentage, Muscle mass, Per capita disposable income, Average annual temperature, Bioelectrical impedance analysis method, Nomadic population