For a long time white adipose tissue (WAT) or more commonly known as fat was seen as the undesirable bumpy tissue caused by enlarged adipocytes (or fat cells) that is a by-product of being overweight. It has now become clear that WAT is an important organ for the secretion and production of adipokines (a type of protein) that play a role in energy metabolism,insulin sensitivity and inflammation. It is the upregulation of the adipokines such as TNF-a, IL-6 and reduction in adiponectin that contribute to the low-grade inflammation associated with obesity. WAT inflammation in turn is associated with the development of co-morbidities such as cardiovascular disease and type 2 Diabetes.
Recent evidence points to the fact that SNP´s in the above genes affect circulating levels of the adipokines and therefore affect the obesity-related phenotype which may be altered by the intake of dietary fatty acids in particular EPA and DHA.
It appears that it is not only the amount of fat in the diet but also the type of fat eaten that affects the phenotype. In a study looking at adiponectin SNP´s and weight changes over 3 years, individuals with the +45G/G and +276T/T genotypes gained more weight over this period, but this effect was reversed when they were commenced on a Mediterranean style diet typically high in olive oil (Razquin et al 2009). It is also known that individuals with a SNP on the Fatty acid Binding Protein 2 (or FABP2) absorb more fats from their diet with a resulting higher BMI and blood lipids. To put it bluntly, they cannot even look at saturated fats without putting on weight, whereas others can manage to avoid weight gain if fats are replaced by monounsaturated fats. Obesity is an inflammatory state and therefore reducing the inflammation is one of the goals of obesity therapy. The ingestion of long chain Fatty acids such as EPA and DHA act as ligands for the PPARy gene which influences insulin sensitivity, the exact mechanism is not yet known. In addition the intake of EPA and DHA have resulted in reduction of TNF-a, IL-6 and an increase in circulating adiponectin levels.
Therefore although it is not perfectly clear how fat type and dosage affects gene expression, tailoring diets whether it is low-fat, low carb or Mediterranean does benefit specific subtypes of individuals especially when it comes to weight loss.
In the mean time, we all should keep our saturated fat intake low, use cooking oils sparingly, avoid processed foods as much as possible and aim for 2 portions of oily fish per week. In addition, get regular exercise we must think of our health every day.
Stryjecki C., Mutch DM. Fatty acid-gene interactions, adipokines and obesity.European journal of Clinical Nutrition (2011)65,285-297