obesity reviews This paper was commissioned by the Foresight programme of the Office of Science and Innovation, Department of Trade and Industry © 2007 Queen’s Printer and Controller of HMSO; published with permission Journal compilation © 2007 The International Association for the Study of Obesity. obesity reviews 8 (Suppl. 1), 77–81 77 obesity reviews (2007) 8 (Suppl. 1), 77–81 OnlineOpen: This article is available free online at www.blackwell-synergy.com Blackwell Publishing LtdOxford, UKOBRObesity Reviews1467-7881© 2007 Queen’s Printer and Controller of HMSO; published with permission; Journal compilation © 2007 The International Association for the Study of Obesity? 20078••7781Review ArticleNutrigenomic approaches for obesity research R. M. Elliott & I. T. Johnson Accepted 27 November 2006 Address for correspondence: Dr RM Elliott and Professor IT Johnson, Institute of Food Research, Norwich Research Park, Colney, Norwich, NR4 7UA, UK. E-mail: ruan.elliott@bbsrc.ac.uk; ian.johnson@bbsrc.ac.uk Nutrigenomic approaches for obesity research R. M. Elliott and I. T. Johnson Institute of Food Research, Colney, Norwich, UK Keywords: Genetics, genomics, nutrition, obesity. Background At the individual level, weight gain is essentially the result of energy intake exceeding expenditure for significant peri- ods of time, but this obvious truth provides no insight into the strategies needed to deal with the ever-increasing prob- lem of obesity in Western populations. It is equally obvious, however, that certain individuals are more prone to devel- oping obesity than others. This phenomenon invites the nutrition research community to explore the physiological basis for such differences and ultimately to design more targeted and personalized approaches to the control of body weight (1). Novel research strategies are required to understand the molecular mechanisms controlling energy balance. In par- allel with such studies, there is still much to be learned about the metabolic consequences that follow when an appropriate energy balance is not maintained, and how this relates to risks of diseases such as hypertension, heart dis- ease, stroke, diabetes and certain cancers. The developing fields of nutrigenetics and nutrigenomics, with their accom- panying battery of high-throughput technologies, provide an unprecedented opportunity to cope with the complexity of this condition and to develop the knowledge base required. Terminology: nutrigenetics and nutrigenomics The term ‘nutrigenetics’ is generally used to refer to the impact of genetic variation on optimal dietary requirements for an individual (i.e. in the simplest terms: gene → diet interactions). Although the term ‘nutrigenomics’, in its broadest sense, encompasses nutrigenetics, more com- monly the main focus of nutrigenomics is considered to be on how diet regulates gene function (transcription and translation) and metabolism (i.e. diet → gene interac- tions) (2). Nutrigenetics and obesity Genetic differences play an important role in the develop- ment of obesity, although it is clear that these are by no means the only contributing factors. Environmental and social factors are also very important. The relative contri- butions of genetic and socioeconomic factors to the devel- opment of obesity, and the ways in which these interact in human societies, are largely unknown. The genetic code (DNA sequence) carried by any two unrelated people is approximately 99.9% identical. It is the variation in the sequence of the remaining 0.1% that determines the genetic component of inter-individual dif- ferences in disease risk, and presumably also their differing responses to the nutritional environment. Sites in the DNA where the sequences of individuals differ commonly (e.g. in at least 1% of the population) are called polymorphisms; the most common form being a single letter change in the code termed a ‘single nucleotide polymorphism’ (SNP). As each cell contains two copies of every gene (except those present on the sex chromosomes), one individual may carry various combinations of a polymorphism. The term ‘geno- type’ refers to the combination of sequences in the two copies of a gene for a particular polymorphism.