Leggings are the must-have fashion item this year, but it seems this popular trend could be making you fat, the Daily Mail reported.

Experts are warning that leggings can make muscles “lazy,” which can result in a flabby abs and legs.

"They hold in and support the quadriceps (thigh muscles), buttocks and core muscles in your tummy, and do the job the muscles are supposed to do," said Sammy Margo, a British physical therapist. "As a result, the muscles are allowed to relax and switch off, so when we reveal our bodies for the first time as summer approaches, they are not as svelte or firm as they otherwise would be."

Another problem is that that these leggings are so comfortable, and guaranteed to fit,  that some women are less likely to take steps to keep in shape during the winter months

"Leggings hide the bits of our bodies we don’t like, such as the cellulite on our legs or our 'muffin top', so we are able to ignore the problem and we are less motivated to exercise these parts," Margo said.

But ladies, fear not, there are some simple daily exercises you can do to tone up before you slip on that bikini, according to Margo. Those exercises include walking with ankle weights as well as clenching and releasing the stomach and buttocks muscles throughout the day.

Margo said it takes about six weeks for the leg and stomach muscles to become noticeably firmer.

"So people should already be weaning themselves off their leggings if they want to look their best in time for summer. The sunny weather should have helped them to ditch them a bit earlier this year and get a head start," she added.

Click here to read more from the Daily Mail.