There's a lot of information about “inclination to gaining weight”. This aspect is also sometimes presented as a “convenient excuse”, which has no reference in a form of scientific studies. On the other hand, you don't need to be an excuisit observer to notice that there are people who put on weight very easily, as well as those who can eat everything without any limits and it doesn't really influence their shape. Therefore, it's good to think about this matter and try to answer the question, whether there is any convincing proof that one can be “genetically predisposed” to overweight and obesity...
Excessive body mass – complex problem
The issue of overweight and obesity may be presented in various ways. It is no longer described as just “the disorder of energy balance”, but it is more likely to have complex etiology with different factors affecting it. Of course, you can still hear some statements, which convince that “everything happens because of gluttony”, or that “carbs are to be blamed”, but the modern science looks at this problem from wider perspective and it takes under consideration also psychological, cultural and... genetical aspects. And these are not only some academic reflections, but the issues, which may be well used in practice by letting to understand the etiology of obesity, and, most of all, choose the remedies better.
Genetic base of obesity is a fact
If someone states that “obesity is a simple result of overeating and genes don't matter”, s/he ignores facts. Whereas, Isaac Asimov used to say that, although knowledge causes problems, ignorance is not the way to solve them. It's obvious that excessive body mass is caused by disorder of energy balance, but this anomaly is not neccesarily its primal cause, as it is also complex itself. Psychological factors are of some importance here (which may, e.g. condition gormandizing because of stress), as well as genetical factors, which may disturb the mechanisms of hunger and influence the processes of energy expenditure.
I suppose, many people will be surprised with the fact that the participation of genetical factors in the development of obesity is estimated at about 40-70%! At least, these are the conclusions of the experts who take care of this topic: Anthony G. Comuzzie, David B. Allison. You can read about it in their work, of which summary you can find under the link below:
Of course, it does not mean that environmental factors in general are of less importance than genetical ones. It usually happens that the first ones predestine the genetical conditions to influence shape.
What is known about the “genetical predispositions of obesity”?
Until now many genes have been extracted, which may influence the process of gaining weight. The most important are the following:
the leptin gene (LEP), of which the product is leptin – an important hormone regulating, among others, functioning of the energetic economy. Mutation of this gene causes creating “shorter” leptin, which does not influence excretion of the Y neuropeptide, which causes increased hunger. Another consequence of this disorder may be the insufficiency of sex hormones.
the gene of leptin receptor (LEPR) – the mutations of this gene disturb the hypothalamic mechanisms of food supply regulation, and they may also result in multiple anomalies within the excretion of other hormones. The cause of such abnormalities is increased hunger, lowered thermogenesis, disorder of reproductive functions and many more...
the gene of the melanocortin 4 receptor (MC4R) – the mutation of this gene causes lack of the feeling of satiety after consuming food, which results in excessive energy supply. Other result of this disorder is hyperinsulinemia.
the gene of peroxisome proliferator-activated receptor gamma (PPARg) – it is responsible for differing fibroblasts towards adipocytes, it also influences the metabolism of mature fatty tissues. The disorders within this gene cause the consequent increase of adipocytes.
the gene of the beta-3 andregenic receptor (ADRB3) – the adregenic receptors take active part in the process of thermogenesis and lipolysis in the adipocytes, the mutations within these receptors cause decreased pace of metabolism and weaker reaction to physical effort and calorific deficit.
the gene of the cannabinoid receptor 1 (CNR1) – the cannabinoid receptors take part in the process of hunger control, therefore, mutations and polymorphism of CNR1 causes increased appetite.
The fat mass and obesity associated gene (FTO) – the gene of proneness to obesity, the issues connected with this gene will be described in separate article.
Genetical predispositions of gaining weight are a fact, not only a naïve speculation. Therefore, you should remember about the fact, that it is proven that we differ on the level of the tempo of metabolism and, most of all, on the level of hunger control. It explains why some people gain weight easier than others despite quite carefree attitude towards food. However, it does not mean that we are powerless in fight against overweight and obesity. It's undeniable that environmental conditions, which are the actions we take, are the key factors of the work on shape.