The present study investigates whether the replacement of dietary casein by soya protein isolate could be able to improve and/or even revert the morphological and metabolic abnormalities underlying the adipose tissue dysfunction of dyslipidaemic rats chronically fed (8 months) a sucrose-rich (62·5 %) diet (SRD). For this purpose, Wistar rats were fed a SRD for 4 months. From months 4 to 8, half the animals continued with the SRD and the other half were fed a SRD in which the source of protein, casein, was substituted by soya. The control group received a diet in which the source of carbohydrate was maize starch. Compared with the SRD-fed group, the results showed that: (1) soya protein decreased body-weight gain, limited the accretion of visceral adiposity and decreased adipose tissue cell volume without changes in total cell number; (2) soya protein increased the protein mass expression of PPARγ, which was significantly reduced in the fat pad of the SRD-fed rats; (3) the activity of the enzymes involved in the de novo lipogenesis of adipose tissue was significantly decreased/normalised; (4) soya protein corrected the inhibitory effect of SRD upon the anti-lipolytic action of insulin, reduced basal lipolysis and normalised the protein mass expression of GLUT-4. Dyslipidaemia, glucose homeostasis and plasma leptin levels returned to control values. The present study provides data showing the beneficial effects of soya protein to improve and/or revert the adipose tissue dysfunction of a dyslipidaemic insulin-resistant rat model and suggests that soya could maintain the functionality of the adipose tissue-liver axis improving/reverting lipotoxicity.