THE EFFECTS OF WEIGHT-LOSS TREATMENTS ON UPPER AND LOWER-BODY FAT

The intra-abdominal visceral deposition of adipose tissue, which chara cterises upper body obesity, is a major contributor to the development of hypertension, glucose intolerance and hyperlipidaemia. Conversely, individuals with lower body obesity may have comparable amounts of ad ipose tissue but remain relatively free from the metabolic consequence s of obesity. This raises an obvious question-are there particular wei ght reducing treatments which specifically target intra-abdominal fat? In theory, surgical removal of upper body fat should be effective. In reality, neither liposuction nor apronectomy ('tummy tuck') have any beneficial metabolic effects, they simply remove subcutaneous adipose tissue which is often rapidly replaced. Vertical banded gastroplasty a nd gastric bypass operations may be dramatically effective in improvin g blood pressure, insulin sensitivity and glucose tolerance. However, these benefits result from a parallel reduction in visceral and total body fat. Studies of body fat distribution in postmenopausal women con firm that the marked decrease in adiposity, following a programme of v ery low calorie diet and exercise, reflects a comparable reduction in visceral and thigh fat. The reduction in waist circumference after a l ow fat/exercise programme suggests a similar situation in men. Exercis e has an important role in treatment but, once again, the fat loss is generalised. Nevertheless, the improved metabolic parameters seen in e xercising obese subjects, independent of weight loss, suggest other be neficial actions. Growth hormone (GH) has a marked lipolytic action. G H replacement treatment for GH deficient adults with pronounced abdomi nal fat deposition, has been shown to reduce intra-abdominal fat by 47 % compared to 27% decrease in abdominal subcutaneous fat. Similar bene ficial actions on abdominal fat have been reported following treatment with testosterone in obese men. The potential hazards of such treatme nts make them unsuitable therapy for obesity. Dexfenfluramine is effec tive in reducing total body fat but the results from a six month rando mised controlled trial indicates that it does not specifically influen ce changes in waist circumference associated with weight loss. In conc lusion, any treatment which reduces total body fat will, by its nature , reduce intra-abdominal visceral fat. There are presently no specific treatments which can be recommended for intra-abdominal fat but incre asing knowledge of the biochemical aberrations associated with viscera l adiposity may lead to more specific therapies for the future.