Weight Management Test

Information For Healthcare Professionals 

Obesity has become an increasingly important clinical and public health challenge worldwide.  According to the International Obesity Taskforce estimates, there are about 1.1 billion overweight and 350 million obese individuals worldwide (1) and this number is expected to grow in alarming levels in the next decade.  In the US, prevalence of obesity has more than doubled in the past 25 years.  There are nearly two-thirds of adults who are either overweight or obese (2).  Overweight/obesity is characterized as an excess of adipose tissue.  The World Health Organization (WHO) and other public health agencies recommend measurement of three different parameters to determine overweight/obesity status for an individual which include, body mass index (BMI), total body fat and waist/hip ratio (WHR). The cutoff points for each of these parameters have been well defined (3).  The overweight and obese subjects are at a higher risk of developing one or more serious medical conditions including hypertension, dyslipidemia, heart diseases and diabetes.  Together these conditions are the second leading cause of preventable deaths.  

Human obesity arises from the interactions of multiple genes, environmental factors and behaviors, rendering management and prevention of obesity very challenging.  According to WHO, lack in physical activity and easy availability of palatable foods are the principle modified characteristic of our modern lifestyle that has contributed a lot to the observed obesity worldwide. Despite the fact that we are all exposed to the same environment, not everyone becomes obese.  This could be attributed to individual genetic differences.  Genetics determines an individual’s susceptibility to obesity when exposed to an unfavorable environment as well as the way he/she can respond to diet and exercise. There have been multiple reports that describe the heritability of obesity and also utilize genetic association studies to identify the gene-gene, gene environment and gene-diet interactions involved in the development of obesity. These studies have identified a certain number of single nucleotide polymorphisms (SNPs) that respond to diet and/or exercise.  For example, some SNPs make some people more sensitive to the amount of fat in the diet, while others make some people more resistant to exercise-induced weight loss.

Interleukin Genetics has developed a genetic test panel in the area of Weight Management (WM), which includes the genes that have been validated as significant modifiers of body weight and responsiveness to diet and exercise.  The genes were selected from the Obesity Gene Map Database based on a comprehensive review of the existing scientific literature using very stringent selection criteria by a team of experts from genetics, nutrition, obesity and weight management areas. 

The following process was used to develop the Weight Management genetic test panel:

1. Dr. Louis Perusse, one of the authors of the Obesity Gene Map review (4), provided a list of all genetic variations that were associated with body weight, body mass index, or body fat and had been replicated in at least three clinical studies. Out of hundreds of genes reported in the scientific literature relative to obesity, only 16 met this first criterion.
   
2. A team of experts then reviewed all evidence on the 16 gene variations for those which met the following:
   
• Had proven biological function. In fact, all of the genetic variations in the test panel produce a change in the amino acid structure of the protein and change the activity of the protein.
• Had a plausible biological role in weight management. For example, some of the gene variations produce a change in the amount of fat absorbed from a meal or change carbohydrate metabolism.
• Had evidence from clinical studies that individuals with the different genotypes had a differential response to either certain diets or to physical activity.
  
3. Five variations in four genes met all of the above scientific criteria and are included in the Weight Management genetic test panel.

These gene variations thus impact various pathways that influence body weight and have been associated with elevated risk for obesity and for their ability to differentiate a subject’s response to weight management interventions by genotypes.  Weight management panel genes and variants include:

• Fatty acid binding protein 2 (FABP2) Ala54Thr;
• Peroxisome proliferator-activated receptor-gamma (PPARG or γ) Pro12Ala;
• β2 adrenergic receptor (ADRB2) Arg16Gly and Gln27Glu; and 
• β3 adrenergic receptor (ADRB3) Arg64Trp

The weight management (WM) test panel is designed to assist consumers with effective management of body weight by guiding diet and exercise programs based on genetic differences in metabolism and fat absorption. 

References:

1. 1. International Obesity Taskforce. About obesity 2005. London, United Kingdom: International Obesity Taskforce (2005) (http://www.iotf.org/aboutobesity.asp).
2. Svetkey, L.P., et. al. Comparison of strategies for sustaining weight loss: The weight loss maintenance randomized controlled trial. JAMA (2008), 299, 1149-1148.
3. Yang, W., Kelly, T. and He, J. Genetic Epidemiology of Obesity. Epidem. Rev. (2007), 29, 49-61.
4. Rankinen T, Zuberi A, Chagnon YC, Weisnagel SJ, Argyropoulos G, Walts B, Pérusse L, Bouchard C. The human obesity gene map: the 2005 update. Obesity (2006) 14, 529-644.

 

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