News at Medicine - June 2014 - New paper by grad student on body fat

New paper by grad student on body fat
June 4, 2014
A paper recently published by Farrell Cahill, a PhD student supervised by Dr. Guang Sun, professor of medicine, has evidence to suggest that the appetite suppressing hormone Peptide YY (PYY) is a positively associated with the severity of adiposity among women in the Newfoundland population. 
“Although circulating PYY was not significantly associated with obesity status among men and women in the general population, our results do indicate that PYY is positively associated with body fat measurements in women and may act as a protective response against excessive weight gain” explained Mr. Cahill.

It is well known that appetite, a key factor in energy homeostasis, significantly influences the regulation of body weight. Therefore, investigating appetite regulating hormones, such as PYY, may provide valuable insight into the underlying mechanisms responsible for the development of obesity. 
“Initial studies, with small sample sizes, claimed that PYY was very significantly inversely associated with adiposity,” said Mr. Cahill. “This subsequently led to the hypothesis that a deficiency in circulating PYY could be a significant contributing factor towards the chronic over consumption of food and subsequent weight gain.”
Mr. Cahill went on to explain, “A considerable number of follow up studies, including one of our own, failed to find any significant negative association of circulating PYY with obesity status. Therefore, the purpose of our study was to investigate whether or not fasting serum total PYY was associated with obesity status and body fat measures in a large cross sectional study”.
A study which contained a total of 2,094 subjects (male 523, female 1571) from the Complex Diseases in the Newfoundland population: Environment and Genetics (CODING) found that PYY was not significantly associated with obesity status defined by neither percentage or body fat or body mass index (BMI) for both men and women. However among women, fasting PYY was positively associated with various body fat measures. Women with the high (top 33 per cent) waist circumference, percentage ody fat and percentage total fat had significantly higher circulating PYY (10.5 per cent, 8.3 per cent and 9.2 per cent respectively) than women with the lowest (bottom 33 per cent) measurements of these body fat measures. Additionally, age, smoking, medication use and menopausal status were all positively associated with PYY levels in women.
“Our manuscript provides strong evidence that the fasting serum total PYY is not significantly associated with obesity status, define by body fat percentage or the body mass index (BMI), among men and women” said Mr. Cahill. “However contradictory to initial studies, we found that fasting serum PYY was in fact positively associated with waist circumference,body fat percentage and total fat percentage, which may represent a protective response to extreme weight gain in women”.

To date, this is the largest cross-sectional study to systematically evaluate the relationship between fasting serum total PYY with obesity status and body fat measures. 
The authors of the manuscript in the PLOS ONE Journal are in order; Farrell Cahill, Yunqi Ji, Danny Wadden, Peyvand Amini, Edward Randell, Sudesh Vasdev, Wayne Gulliver, and Guang Sun.