Objectives:The aimof this studywas to assess the effect of bothmeal timing and diet composition on BMI, waist, body fat and HOMA-IR in patients with metabolic syndrome (MS). Methods:We studied 77 patients with MS (32 men and 45 women). Detailed analysis of baseline food-diaries showed that 43 patients (56%) were mostly eating after 3 p.m., generally skipping breakfast, and had more frequent carbohydrate snacks. We divided patients into two groups. The first group consisted of patients with most caloric intake after 3 PM, and the second group included patients who were evenly consuming their food throughout the day. Following diet were offered: 3-fold meal (food intake was at 7–9a.m., 1–2p.m. and 6–7p.m.) with very low-carbohydrate (LC) breakfast and dinner, lunch consisted of LC, proteins (P), polyunsaturated fatty acids (PUFAs) and non-starchy vegetables(V); there were absolutely no snacks during the day. Daily calorie intake was reduced by 20% from baseline. Diet intervention lasted 12 weeks. No medication were used during this period. Results: 60 patients completed the trial (32 and 28 patients in first and second groups respectively). BMI was reduced from 33,1 ± 5,0 kg/m2 to 29,8 ± 4,6 kg/m2, the effect was similar in both groups (Cohen’s d = 0,7, P = 0003). Mean body fat decreased from 40,7 ± 7,0% to 35,8 ± 7,5% in 12 weeks and treatment effect was more pronounced in second group (Cohen’s d = 0,76, P = 0007). The most significant changes were observed in HOMA-IR, which decreased from 4,0 ± 1,1 to 2,1 ± 1,1, treatment effect was also more pronounced in second group (Cohen’s d = 1,22, P = 0001). Waist circumference statistically decreased too (from 100,9 ± 16,8сm to 92,0 ± 14,6сm), although with more modest effect Cohen’s d = 0,58, P = 0003. Maximum effect size was in HOMA-IR changes. whereas minimum in waist circumference. Conclusions: Our findings demonstrate that this diet (low carb, hight fat, 3-fold meal diet with lunch before 3 p.m.) is associated with statistically different changes in BMI, waist, body fat andHOMA-IR and the intervention was more effective among patients in second group. Funding Sources: Not funded.