Sexual Dimorphism in the Response of Adipose Mass and Cellularity to Graded Caloric Restriction

Abstract

Research Methods and Procedures:Three-month-old female and male Wistar rats were subjected to a chronic, mild to moderate caloric restriction paradigm (5%, 10%, or 20% reduction in caloric intake from ad libitum values) for 6 months. This was accomplished using a unique automated feeder system tailored to the food consumption levels of individual rats. Body weight and length, weight of lean organs, regional adipose mass, and adipose cellularity were measured before and after the diet restriction. Results: Caloric restriction produced proportional decelerations in body weight increases in both genders, without significant changes in body length or lean organ mass. Marked and disproportional reductions in regional adipose tissue mass were produced at all levels of food restriction (even at 5% restriction). An unexpected finding was that in response to graded caloric restriction, female rats preserved adipose fat cell number at the expense of fat cell volume, whereas the converse was seen for male rats. Discussion: These studies demonstrate a sexual dimorphism in the response to mild to moderate degrees of chronic caloric restriction. At low levels of caloric restriction, it is possible to affect regional adipose mass and cellularity while preserving lean organ mass.

Sex-related differences in energy balance in response to caloric restriction

“…Significant differences in WAD weight were observed between the sexes in ad libitum and restricted animals. These data were in accord with several studies that have reported in males a greater percentage of the body as fat than females (31,34,44). CR induced a more pronounced loss of WAD in females than in males (Ϫ72.8 vs. Ϫ68.6% RCG respectively), although this did not reach statistical significance.…”

“…Furthermore, important sex-associated differences have been found in the response of white adipose mass to CR. These studies suggest that females use energy stored as fat to a greater extent than males (26,44). However, the loss of lean body mass cannot wholly explain the energy conservation seen when female rats are subjected to CR (26).…”

Diet-induced obesity in gravid rats engenders early hyperadiposity in the offspring

“…However, freshly siliconized glassware was used; and centrifugation steps were minimized [23]. Definitive conclusions on AT cellularity in DIO offspring await confirmation using complementary techniques [24].…”

Evaluation of the Effects of Fasting On Fertility in Adult Male Wistar Rats

“…(Athar et al,1984;Hussein et al,(1987).In contrast, a study reported weight gain (Frost and Pirani, 1997) Prolong fasting has been known to result in adaptive mechanisms for body weight maintenance.El-Ati et al, (1995). Also, the liver has been known to have priority only when the nutritional supply is not enough to furnish the metabolic energy for tissues and organs Porter et al, (2004). The observed progressive increase in mean food consumption with the period of fasting in the fasted rats indicates an adequate nutritional status that will not need the liver mobilize the adipose tissues.…”