Effect of genetic factors on nutrition: The genes are not to blame

Overweight and obesity have become a global health problem. According to the World Health Organization, 39 percent of adults in EU countries have overweight. In Germany more than 50 percent of adults suffer from overweight, almost one fifth is according to the Robert Koch Institute currently considered obese. This is primarily due to the modern lifestyle which is characterized by low physical activity and high-calorie foods.

Also genetic factors play a role in the occurrence of obesity. To date, around a hundred genes (loci) have been identified which are related to the body mass index (BMI). However, the functioning of these genes as well as the biological mechanisms behind them are still largely unknown. The investigation of the relationship between genetic factors and nutrition can shed light on whether the genes which are linked to BMI play a role in nutrition.

Systematic literature search

The initial database search of the TUM team revealed more than 10,000 scientific articles which were concerned with the topic. Of these, 39 articles were identified for a relationship between genetic factors and total energy, carbohydrate, or fat consumption. "In all studies, we most frequently encountered the fat mass and obesity (FTO) associated gene as well as the melanocortin 4 receptor gene (MC4R). There are indications of a relationship between these two genes and total energy intake," explains Christina Holzapfel, PhD, from the Institute of Nutritional Medicine at TUM.

However, the evaluation of the studies did not provide a uniform picture: "There is only limited evidence for the relationship between the FTO gene and low energy intake as well as between the MC4R gene and increased energy intake."

Hence, to date there exist no indications that certain genetic factors are associated with the total intake of calories, carbohydrates, and fat. The current state of knowledge is still too limited for deriving individual nutritional recommendations based on genetic information, e.g. for weight management, explains the researcher. Expert associations also agree with the latter statement.

"Human studies with detailed phenotyping, e.g. based on a genetic pre-analysis of the participants, are necessary in order to determine the interactions between genetic factors and diet on body weight. The "Personalized Nutrition & eHealth" Junior Research Group funded by the Federal Ministry of Education and Research, which is part of the enable nutrition cluster, is working precisely on this."