['Apolipoprotein A5 (APOA5) is a determinant of plasma lipids, and its role in body mass index (BMI) determination is discussed. This study was aimed at the investigation of the relationship between common APOA5 gene variants and body weight/plasma lipid decrease in overweight females.', 'We analyzed 98 unrelated overweight and obese nondiabetic Czech females (BMI >27.5). APOA5 T-1131-->C and Ser19-->Trp variants were genotyped. Before and after 9 weeks of lifestyle modification, biochemical and anthropometrical measurements and assessment of nutritional intake were performed. The lifestyle modification program consisted of a reduction in energy intake and an exercise program (aerobic exercise 4 times per week, 60 min each).', 'The mean age of the participants was 30.7 +/- 3.7 years, the mean BMI before the intervention was 31.4 +/- 3.8 and the weight loss was 5.9 +/- 2.5 kg (7 +/- 3%). There were 86 T-1131T homozygotes and 12 carriers of the C-1131 allele and 82 Ser19Ser homozygotes and 16 carriers of the Trp19 allele, respectively; 72 females had the commonest T-1131T/Ser19Ser haplotype. No significant association between BMI decrease and APOA5 variants was found, but T-1131T carriers have a significantly higher body weight both before and after the intervention (p < 0.05; p = not significant for BMI). The fasting glycemia was significantly higher in Trp19 carriers both before and after the intervention (p < 0.01). Further, plasma triglyceride levels decreased in Ser19Ser homozygotes but increased in Trp19 carriers (1.42 +/- 0.62 to 1.28 +/- 0.48 vs. 1.15 +/- 0.47 to 1.41 +/- 0.80 mmol/l; p < 0.05 for differences between the groups). Similarly, in carriers of at least 1 less common APOA5 allele (n = 26), plasma low-density lipoprotein cholesterol levels did not decrease as they did in T-1131T/Ser19Ser carriers (3.11 +/- 0.70 to 3.27 +/- 0.81 vs. 3.39 +/- 0.81 to 3.16 +/- 0.86 mmol/l; p < 0.05 for differences between the groups).'] Does changes of plasma lipids during weight reduction in females depend on APOA5 variants?