The purpose of the present study was to evaluate the effect of Ramadan fasting on insulin sensitivity in subjects with the metabolic syndrome. Males (n 55; age 34.1 (sd 8.9) years) with the metabolic syndrome were studied. Blood pressure, waist circumference, body weight, HDL-cholesterol (HDL-C), TAG, fasting plasma glucose (FPG), fasting blood insulin and insulin resistance indices (quantitative insulin sensitivity check index (QUICKI), homeostasis model assessment of insulin resistance (HOMA-IR) and reciprocal index of HOMA-IR (1/HOMA-IR)) were evaluated before and after 30 d of Ramadan fasting (two meals at 12 h intervals). The dietary intake was estimated by 24 h recall before and after fasting. The total daily energy intake was decreased by 234.6 (sd 88.2) kJ/d in the fasting period (P = 0.005). 1/HOMA-IR, QUICKI and HDL-C were significantly increased (P = 0.005, P = 0.001 and P = 0.004) and FPG significantly decreased (P < 0.005) after fasting. Simple linear regression analysis demonstrated that HOMA-IR, 1/HOMA-IR and QUICKI were related to waist circumference after intervention (r 0.458, P < 0.001; r - 0.396, P < 0.05; r - 0.342, P < 0.05). In conclusion, the present study showed that the combined change in the number and timing of meals and portioning of the entire intake into only two meals per d may increase insulin sensitivity in subjects with the metabolic syndrome even when the decrease in energy consumption is minimal.