Loosening that belt buckle by a notch or two may not be obvious enough. A recent study found many young women fail to recognize the number on the scale creeping up. But not all 20-something gals are oblivious; weight perception varied according to ethnicity and birth-control use.

Researchers asked 450 women, who averaged 25 years of age, about their weight twice a month for three years. About one third of participants didn’t realize they’d gained 4.5 pounds over six months, and a quarter didn’t even recognize when they’d gained almost nine pounds. (Wait…that’s not muscle?)

Black women and those who used the DMPA birth control injection were most alert to increases in their weight. Researchers suggest women who use DMPA might be more aware of adding on the pounds because of the hype around birth control use and weight gain.

The number on the scale is a weighty issue, since being overweight can increase the risk of heart disease, certain cancers, and even sleep apnea. So get out of the elastic pants and try to notice if those jeans become a squeeze too tight. And remember to exercise with a mouth full of this stuff (but not at the same time…) to help feel and look better than ever.