BACKGROUND It is known that weight loss is beneficial for obese and overweight subjects with metabolic syndrome. Very few data exist, however, about whether the presence of metabolic syndrome and insulin resistance (IR) influence the response of these subjects to weight-reducing interventions. The current study intends to examine whether the presence of metabolic syndrome and its components could influence weight loss in obese and overweight women during a short-term, dietary-based intervention program. METHODS A total of 107 women aged 49.1 +/- 13.5 years old, with a body mass index (BMI) greater than 25 were studied. The subjects were prescribed a low-fat diet plus weight-reducing drugs when necessary. RESULTS After 3 months, the subjects with metabolic syndrome lost more weight than those without (6.62% vs. 4.50%; P < 0.05). There was a positive correlation between the percentage of weight loss and the number of the components of metabolic syndrome present at baseline (Spearman rho = 0.329; P < 0.01). Furthermore, patients in the quartile with the highest homeostasis model assessment index (HOMA-index) lost more weight than the remaining subjects (8.17% +/- 3.34 vs. 5.59% +/- 3.87; P < 0.05). These results were significant, even after adjustment for the medical treatment prescribed. CONCLUSIONS Obese and overweight patients with metabolic syndrome showed a greater reduction of their body weight, compared to the patients without metabolic syndrome. The components of the metabolic syndrome present at baseline correlated positively with the percentage of the weight loss. Finally, the patients with the highest levels of HOMA-index at baseline lost significantly more weight than those with lower levels of this parameter.