d-Fagomine is a natural iminosugar that counteracts the short-term effects of a high-energy-dense diet on body weight, fasting blood glucose levels and the proportion of gut Enterobacteriales. This suggests that supplementation with d-fagomine for longer periods may delay the onset of other factors related to metabolic syndrome. Here we evaluate the effects of d-fagomine dietary supplementation on relevant metabolic hormones and lipid peroxidation. Adult Sprague-Dawley rats were fed a high-fat high-sucrose diet supplemented or not with d-fagomine (0.065% w/w) for 9 weeks. Weight gain, plasma triglycerides, glucose, insulin, glucagon, ghrelin, leptin, and urine F2-isoprostanes were evaluated. d-Fagomine attenuated the changes induced by the high-energy-dense diet in triglycerides and all the hormones tested. These results suggest that d-fagomine may help to avert the complications associated with unhealthy eating by counteracting the effects of high-energy-dense diets during the early stages of the development of metabolic disorders.