The aim of the study was to determine whether and how excessive weight gain causes overweight in women after childbirth. The experiment was conducted on pregnant mice divided into two groups. The first was fed a high-fat diet. The second, the control, was fed a balanced diet. After giving birth, the researchers observed the energy metabolism of both groups.

The rodents, maintained on a fat-rich diet, gained more weight during pregnancy than those in the control group. After birth, however, the excess weight was quickly eliminated and both groups of mice were started on a balanced diet. Three months after birth, the first changes in fat mass were noticed - the first group started to gain weight again, despite returning to an optimal diet. Nine months after birth, their weight was twice that of the second group.

The researchers drew a clear conclusion - the metabolism of the mice in group one slowed down and energy expenditure decreased. Estrogen signalling was impaired in the adipose tissue of these mice. The results show that a high-fat diet during pregnancy causes long-term postnatal obesity regardless of early fat retention after birth. It also suggests that such a drastic dietary change adversely programmes long-term postnatal energy metabolism by reducing estrogen signalling.

- If similar results are found in human studies, it will allow us to better understand the problem of post-pregnancy obesity and therefore: develop more effective prevention methods, said researchers from the University of California, San Diego.