Altered activity of transmembrane cation transport has been linked to non-communicable diseases (NCDs) related to obesity. The present study therefore sought to determine the activity of Na+-K+-ATPase in erythrocytes of underweight, normal weight, overweight and obese women. A total of 36 normotensive non-smoker Nigerian women categorized as underweight, normal weight, overweight and obese were enrolled to participate in the study. Membranes of their erythrocytes were harvested and processed for Na+-K+ ATPase activity. Written consent was obtained from the participants for the study. The result showed that Na+-K+ ATPase activity of underweight as well as those of the overweight and obese women were significantly reduced when compared with that of the normal weight women. Impairment of the activity of Na+-K+ ATPase in obese women was significantly greater than those observed in overweight and underweight individuals. Multivariate regression analysis indicated that age is the strongest independent determinant of the activity of Na+-K+ ATPase in underweight women. However, body weight was indicated as the strongest independent determinant of the activity of Na+-K+ ATPase in overweight and obese women. The findings in the present study demonstrate that overweight and obesity as well as underweight are associated with impaired erythrocyte Na+-K+ ATPase activity in women. Furthermore, advanced age may seem to explain the reduced activity of the erythrocyte Na+-K+ ATPase activity in underweight while increase body weight may explain the activity in overweight and obese women.