New answer suggest that not all calories as fat. So far only been confirmed in rodents, but it seems quite probable that weight gain does not depend only on how many calories are ingested but also the type.
Most arresting was the discovery that given two diets: one fat and one carbohydrate, but both with the same calories, the diet is rich in carbohydrates fatter.
These new findings are complex to explain, as related to genetics go, and more particularly to geneticist. To get in position we must distinguish three specialties that relate nutrition and genetics:
Geneticist, how food, contain chemical signals, can encourage changes in the genes
Nutritiousness, how the genes of each cell are responding to that cell in front of a nutrient
Nutriments, how do different nutrients that genes respond differently
So the researchers, our diet causes changes in the reading of our genes. Or put another way, we have inherited genes do not change, which is altered is the activity of our genes.
Much remains to be investigated, but no doubt it will be interesting to reveal why a diet rich in fat and calories with the same high-carbohydrate diet, just less fattening, when hitherto thought otherwise.