[manjana]

That is true to some degree. That to which you are referring is metabolism. Metabolism however, is influenced to a large extent by enviroment and level of exercise.

But correct that it might be genes was observed in the dutch population generations after early nineteen hundredth's famine crisis: [ https://www.nytimes.com/2018/01/31/science/dutch-famine-gene... ]. This eventualley led to a new area of study called epigenetics (of which one of the pioneers actually earnes a Nobel's Prize I think). Epigenetic research has shown that genes are not final. In the case of the dutch famine, the famine-victims which survived had undergone epifenetic changes (their genes changed) in response to the famine, their body would become extremely energy efficient and their energy partitioning would lean towards buildup of adipose tissue (fat). However (!!) research later shown that these gene alteration which their offspring inherited and which were observed throughout the dutch poulation generations later, was reversible by environmental factors and exercise.