Background: Modern Western lifestyle is characterized by the consumption of high-heat-treated foods because of their characteristic taste and flavor. However, it has been shown that treating food at high temperatures can generate potentially harmful compounds that promoteinflammation and cardiovascular disease in subjects with diabetes. Objective: The aim of this study was to determine whether highheat- treated foods also pose a risk for healthy subjects. Design: A randomized, crossover, diet-controlled intervention trial with 62 volunteers was designed to compare the potential metabolic effects of 2 diets, one that was based on mild steam cooking and another that was based on high-temperature cooking. These 2 diets differed mainly in their contents of Maillard reaction products (MRPs). MRPs were assessed in the diet and in subjects' feces, blood, and urine samples, with Ne-carboxymethyllysine as an indicator of MRPs. Biological indicators of glucose and lipid metabolism as well as oxidative stress were analyzed in subjects after 1 mo on each diet. Results: In comparison with the steamed diet, 1 mo consuming the high-heat-treated diet induced significantly lower insulin sensitivity and plasma concentrations of long-chain n23 (omega-3) fatty acids and vitamins C and E [217% (P , 0.002), 213% (P , 0.0001), and 28% (P , 0.01), respectively]. However, concentrations of plasma cholesterol and triglycerides increased [+5% (P , 0.01) and +9% (P , 0.01), respectively]. Conclusions: A diet that is based on high-heat-treated foods increases markers associated with an enhanced risk of type 2 diabetes and cardiovascular diseases in healthy people. Replacing high-heattreatment techniques by mild cooking techniques may help to positively modulate biomarkers associated with an increased risk of diabetes mellitus and cardiovascular diseases.