Researchers have unravelled the fact that the female sex hormone, oestrogen, reduces a woman's ability to burn fat after a meal.
The finding, by Sydney endocrinologist Associate Professor Tony O'Sullivan, of the University of NSW and St George Hospital, Sydney, may help explain why ladies store fat more efficiently than men.
The study has been published in the journal, Obesity Reviews.
To reach the conclusion, the researchers pooled together research by himself and others to explain why women have on average 6 to 11percent more body fat than men, despite males generally eating more.
The hypothesis suggests a fat-storing mechanism kicks in during puberty and early pregnancy for biological reasons. During times of scarce food, extra kilograms may mean survival.
Tony said that body fat is also linked to fertility as ovulation can stop if underweight.
"Female puberty and early pregnancy - times of increased oestrogen - could be seen as states of efficient fat storage in preparation for fertility, foetal development and lactation," ABC Online quoted him, as saying.
"There's strong preliminary evidence, but further research is needed.
"The hypothesis stems from the fact women have a higher percentage of body fat than men, yet when you look at dietary intake, women don't eat more fat and calories than men, they normally eat less.
"It suggests when puberty occurs women change the way they metabolise fat, storing more fat from their diet instead of burning it up," the researcher added.
Research supporting the notion shows that in the first 12 to 15 weeks of pregnancy women put on an average 2 to 3 kilograms of fat despite not eating more or exercising less.