After enduring numerous lectures by well-meaning doctors, we weight-challenged patients have always known weight gain and loss was far more complicated than "calories in, calories out" and sheer willpower, haven't we? Sharon Moalem's book, Inheritance : How Our Genes Change Our Lives and Our Lives Change Our Genes, touches on "nutrigenetics" among other gene-related topics...
Nutrigenetics is a branch of nutritional genomics which aims to identify genetic susceptibility to diseases and genetic variation in the effects of nutrient intake on the genome. Nutrigenetics is not to be confused with Nutrigenomics, which focuses on the role specific foods have in activating genes that affect susceptibility to certain illnesses such as Alzheimer’s Disease and cancer. Nutrigenetics is still in its relative infancy compared to other branches of medical science. It aims to offer people personalized disease prevention advice based on genetic makeup.
Due to evolutionary processes, humans differ in their DNA, more precisely in so-called SNPs (short for “single nucleotide polymorphism”). Among others, SNPs influence the way individuals absorb and process food components. Physiological activity in the human organism that concerns the consumption or transportation of nutrients is also connected with the reciprocation of various genetic variants. This assumption forms the basis for nutrigenetic sciences. Moreover, different nutrigenetic processes in the human body can imply an advantage in terms of natural selection. Thus, for example, evolution urged people to digest lactose from cow milk.
The identification of the necessary genotype is carried out by means of a blood analysis or a cheek swab. Subsequently, the DNA is analyzed in different ways. A common way to study the genetic data is the so-called “candidate gene approach” when one possible risk gene is identified. After experiments on cell cultures, animals or humans scientists can establish a positive or negative correlation between the expression of this candidate gene and nutritional aspects. Another popular scientific method is a genome-wide association study which also leads to the identification of relevant gene variants. In particular, nutrigenetic analyses are based on the effect of nutritional components on the genome, proteome, metabolome and transcriptome.
A major goal for nutrigenetic researchers is to identify genes that mke certain individuals more susceptible to obesity and obesity-related diseases. The "thrifty gene" hypothesis is an example of a nutrigenetic factor in obesity. The "thrifty gene" theoretically causes bearers to store high-calorie foods as body fat, a most likely as an evolved protection against starvation during famines. However, the potential "thrifty genes" that may be affected by nutritional factors have yet to be identified. Future advancements in nutrigenetics research may potentially prove the existence of "thrifty genes" as well as find counter-effects in order to prevent obesity and obesity-related diseases.