In recent years, intraabdominal adipose tissue (IAAT) has proven to be strongly related to metabolic abnormalities associated with obesity. Weight reduction programs have promoted weight loss and reduced the health risks that go along with IAAT. Waist circumference correlates well with IAAT and is often used for a marker of visceral adipose tissue, as it appears to accurately reflect the relation between visceral adipose tissue and health risk. Racial differences exist in regards to the risk of obesity-related health problems and therefore attention has focused on the association between risk factors and abdominal fat distribution in white and black populations. Based upon previous research, black women and children appear to have lower distribution of adipose tissue as IAAT than as subcutaneous abdominal adipose tissue (SAAT) than do white women and children. At present, little is known about the effect of weight loss on changes in visceral and subcutaneous abdominal fat distribution in overweight white and black individuals.

The purpose of a recent intervention was to prospectively examine the abdominal fat distribution patterns of overweight weight and black women, before and after weight loss, in relationship to those of never-overweight control women. Subjects included white and black pre-menopausal women between the ages of 20 and 46 years. 23 overweight white women and 23 overweight black women participated. Overweight was defined as having a body mass index (BMI) between 27 and 30 and a family history of obesity in a least one first-degree relative. Twenty-three white and 15 black, never-overweight women served as controls. Subjects were evaluated at baseline when they were overweight, and again at normal weight and underweight, following dietary intervention. Subjects were maintained in a weight-stable state for four weeks, during the final two-week were given meals providing 20 percent of energy as fat, 16 percent as protein, and 64 percent as carbohydrate. All prepared meals for weigh reduction afforded 800 kcal/day. Adherence and body weight were monitored twice weekly until subjects lost 10kg and reached a normal weight, defined as a BMI of <25. On reaching a normal BMI, subjects repeated the protocol to achieve a weight even further below that previously attained. The subjects were sedentary and not instructed to increase physical activity during the intervention period. In each of the weight phases (overweight, normal weight and under normal weight) body composition was determined using the four-compartment model. This model included the analysis of bone mineral content, total body water, and total body density to take into consideration the fact that black women generally have a greater bone mineral content than do white women. The model is used to calculate the percentage of body fat from independent measure of total body density, total body water, and bone mineral content.

Weight loss, losses of total fat, trunk fat and waist circumference were similar in both the white and black women. White women were found to have lost more IAAT and less SAAT than did black women. Changes in waist circumference correlated with changes in IAAT in white women, but not in black women.

This data indicates that white women had significantly more IAAT and significantly more IAAT relative to SAAT than did black women despite comparable decreases in total and trunk fat. Further studies investigating the changes in metabolic risk factors associated with weight loss and gain and body fat distribution in both black and white individuals are needed to gain understanding of the clinical significance of these different racial responses in abdominal fat utilization.