Kira-Ann L. Edwards, M. Hum. Nutr.; Stefanie Kalfas, B Sc; Luke A. Prendergast, Ph.D; Joseph Proietto, M.B., B.S, Ph.D.
Obesity is a well-known health concern, with a high level of morbidity and a substantial economic burden. Previous research has demonstrated that weight loss is vigorously physiologically defended in obese subjects who lose weight, which is known to cause an almost universal regain of weight lost. What is not yet known is whether the degree of weight loss has an impact on these physiological adaptations.
To date, 44 subjects have been enrolled in the study, which is a dietary intervention trial in two phases. During the weight loss phase subjects are placed on a very low energy diet (VLED) program for 12 ± 4 weeks to achieve a 15% weight loss. At baseline, 5% weight loss, 10% weight loss and 15% weight loss circulating levels of leptin, ghrelin, peptide-YY, glucagon-like peptide 1, gastric inhibitory polypeptide and pancreatic polypeptide are examined, and anthropomorphic measurements are collected. The follow-up phase is a 24 month weight maintenance phase with quarterly anthropomorphic measurements and biannual blood sampling.
To date, data analysis of 5 subjects who successfully achieved a 15% weight loss has been completed. Significant decreases in leptin (p<0.001) and amylin (p<0.001) concentrations were demonstrated at 5% reduction in weight, and were found to be proportional to percentage change in weight. No significant changes in peptide-YY, glucagon-like peptide 1, pancreatic polypeptide and gastrointestinal inhibitory polypeptide were demonstrated in response to weight loss using data from this pilot sample. Ghrelin results are not yet available.
Preliminary data suggests that weight defence mechanisms in obese subjects are proportional to degree of weight loss, and are triggered by even modest reductions in weight to the order of 5%. Further data is required to confirm this.