A new study may make it easier to understand why so many women feel they gain more weight than men later in life.

The research, published in the journal Diabetes, reported in MyHealthNews Daily, says that after menopause, the activity of Aldh1a1, an enzyme involved in the production of fat, begins to increase.

Mice have Aldh1a1 as well. Therefore, researchers used the rodents to see what would happen when mice of both genders had eaten a diet high in fat. The Aldh1a1 activity produced more abdomen fat in female mice than in the male mice.

However, as noted by MyHealthNews, the female mice that had the enzyme genetically engineered remained lean on the high-fat diet.

After menopause, levels of estrogen start to decrease, which causes Aldh1a1 activity to surge. That may be what’s making older women so susceptible to weight gain.