GENDER DIFFERENCES IN CHANGES IN SUBCUTANEOUS AND INTRAABDOMINAL FAT DURING WEIGHT-REDUCTION - AN ULTRASOUND STUDY

Objective: In weight-reducing programs, men usually display greater im provement in metabolic risk factors than women. This gender difference may be related to enhanced weight and fat loss due to a greater energ y deficit in men. To clarify the relationship between changes in metab olic profile, body fat composition, and weight loss, both sexes were s tudied under a regimen in which similar amounts of weight were lost. R esearch Methods and Procedures: A cross-sectional study using anthropo metric (body mass index and waist-to-hip ratio), impedance (bioelectri cal impedance analysis) and ultrasound measurement methods (thickness of subcutaneous fat layers, intra-abdominal sagittal diameter) were co nducted. The metabolic risk profile was determined by measuring lipids , lipoproteins, and blood pressure. The weight loss program lasted 15 weeks: 3 weeks under controlled conditions in the hospital and 12 week s on an ambulatory basis. Patients were instructed to follow a mixed d iet. Calorie intake was restricted to 1500 kcal/day for the men and 12 00 kcal/day for the women. Thirty-two subjects with obesity (16 men an d 16 women), with a mean body mass index of 35 kg/m(2)-matched with re gard to age, height, and body weight-took part in the study. Results: As expected, weight loss was similar for both sexes (-13.4 kg vs. -12. 8 kg). Also, body fat mass changed to the same extent in absolute and relative terms. The waist-to-hip ratio was identical before and after treatment in both sexes. The men lost more visceral fat than the women . This result is based on changes in intra-abdominal diameter as well as abdominal subcutaneous fat in relation to waist circumference. Chan ges in abdominal diameter were paralleled by reductions in triglycerid es and increases in high-density lipoprotein-cholesterol. Subcutaneous fat loss was more pronounced in women than in men. Discussion: Where absolute and relative reductions in body weight and body fat are simil ar, men mobilize more intraabdominal fat than women, whereas women los e more subcutaneous fat. The greater reduction in intra-abdominal fat seen in men is accompanied by a more pronounced improvement in the met abolic risk profile. Therefore, greater improvement of risk factors in men is not only related to a greater negative energy balance, as show n in most studies, but is also sex-specific.