Shapewear can make you look slimmer and sleeker in a cocktail dress, work clothes, or jeans and a T-shirt. If you've tried it before, you might be in for a surprise. "In the beginning, shapewear used to be too tight and it would push the fat in the wrong way, which was just not flattering," says Los Angeles celebrity stylist Sophia Banks-Coloma. "I remember going on a date and thinking I had food poisoning because I was wearing bad shapewear. I had to remove it in the bathroom." As long as you wear it properly, shapewear should be relatively comfortable. "There are different levels. It can be ultra or light slimming," says Milena Joy, an image consultant in Denver. "You don't have to wear something that will totally change your shape. You can choose what spots, to target just your thighs, butt, stomach, or multiple areas." ...That is, if you know how to choose and use your shapewear, and know why it should never be too tight. Get the right fit Although you can buy shapewear online, it's worth it to go to a store to try on several brands and styles. If you're buying for a specific dress or outfit, bring it with you. A quick hip and waist measurement can help you make sure you're looking at the right size, Banks-Coloma says. Be realistic: You can count on shapewear to smooth out lumps and give you a sleeker silhouette. Going down a shapewear size, however, won't help you zip yourself into a smaller dress. "Women sometimes try to size down to add extra firmness," Joy says. "But that makes you look bigger because it can cause bulges, and it can be uncomfortable." Too-tight shapewear may lead to health problems, says neurologist Orly Avitzur, MD, medical advisor for Consumer Reports. "Any time we put on really tight garments we take the risk of compressing organs or nerves." Avitzur says that in her practice, she has had patients complain of tingling and numbness in the front to outer thigh region, from hip to knee. Avitzur has traced the cause back to restrictive clothing like shapewear or skinny jeans. Some stars, such as actress Octavia Spencer and singer Adele, admit to layering pieces of shapewear for special occasions. "I've done two or three layers for an appearance or commercial," Banks-Coloma says. "Obviously it isn't comfortable, but it can be effective." That trend may be better left in Hollywood, Avitzur says. "Special events are meant to be enjoyed, and that's hard to do if your garments are squeezing you like a vise." Layering shapewear makes compressing nerves or organs more likely, she says. Not only for special occasions You can wear shapewear to work, as long as it's not bothering you. "The benefit," Joy says, "is that it can help you feel more confident and it can boost your self-esteem." If you wear shapewear every day, pay close attention to how comfortable you are. "If you're afraid to go to the bathroom because your shapewear is difficult to remove, you might be putting yourself at risk of a UTI [urinary tract infection]," Avitzur says. If you are prone to bladder infections, yeast infections, or GI symptoms like reflux, wearing shapewear every day may not be such a good idea, Avitzur says. Pregnancy and shapewear If you're pregnant, you might want to check with your doctor about whether you can use special maternity shapewear. It may actually help you feel better, says ob-gyn Laura E. Riley, MD, medical director of Labor and Delivery at Massachusetts General Hospital and author of You and Your Baby: Pregnancy. "Maternity shapewear is fine for women to wear daily if they are comfortable," Riley says. "It should help for women with varicose veins, which can be uncomfortable when standing, and it should provide support to lift the uterus off the cervix and ease pain [if the pelvis becomes misaligned]." As a neurologist, Avitzur says "pregnant women are already at risk for compressing a nerve in the abdomen if their belly is large." If you do wear shapewear while expecting, make sure getting it on and off isn't such a struggle that you put off urinating, as that can set you up for urinary tract infections. Building a shapewear wardrobe "Start with the basics like a mid-thigh shaper, a slip dress, and then add something more specialized like underwear," Joy says. "You can build your shapewear wardrobe as you would build a regular wardrobe." For the most flexibility, look for pieces in a shade that's close to your skin tone. Some of Joy and Banks-Coloma's favorite pieces: Tights: This is a great place to start with shapewear, Banks-Coloma says. You can choose options that slim the whole leg, or the thighs, rear, hips, and waist. They smooth out panty lines, and there are butt-boosting styles. In the past, waste bands might have rolled over, but that shouldn't be an issue anymore, Banks-Coloma says. Full body suit with a chest cut-out Body suits slim the hips and hold in the stomach, but they can also flatten your chest, like a sports bra. New styles have an open bust that actually lifts your breasts. (You wear it with a separate bra.) When you try on a body suit, make sure that the overall effect is smoothing and that it doesn't create bulges in new spots, like where the seam hits your thigh, Banks-Coloma says. If you're hoping to minimize a larger chest, choose a suit that covers it. If you think that shapewear will flatten your behind, you could try a butt-boosting style. Some come with padding, some use panels that lift your rear, and others have cut-outs. Camisole. "The number one spot women want to cover is their stomach," Joy says. If it looks like regular clothing, you can let it show. "A cami can also help smooth out muffin top (tuck it into your pants) and bra bulge on your back. Panties: Shapewear panties can help eliminate panty lines and slim down your thighs, hips, rear, and even your stomach. If you're looking for sleeker thighs, you can choose a boy short cut -- just make sure that the leg bands don't cut into your skin. If you're not looking for help in the thigh region, a brief cut can create a more seamless look, says Joy. To tighten your abdomen, choose a high-waisted style with a panel that covers the stomach. You can look for rear-enhancing panties, too. Slip: If you're going to wear a slip under a dress, why not choose one with a little extra smoothing power? "I use slips on the red carpet all the time," Banks-Coloma says. A good slip can eliminate bulges and panty lines under thin or sheer dresses. Bring your dress into the store with you. There are many options for necklines and straps, and you want one that won't poke out of the dress, Joy says. If you're wearing a skirt, you can choose a half slip that starts at the waist (and pair it with a camisole, if you like). Mid-thigh shaper: These look like bicycle shorts that extend up to the waist (or higher) and can cinch your thighs, butt, hips, and abdomen. "If you have bulk on your thighs and not around your stomach you can get a short that comes up to the waist," Banks-Coloma says. "But if you have bulk all over, you should find one that comes up to just under the bust." If you go too tight, the band on the top will roll over. "Be careful if you have a flat butt that the shaper doesn't make it look flatter," Joy says. If that's the case, look for a butt-boosting style. Finally, always do a "sit" test with your outfit, Joy says, so your shapewear doesn't peek out from under your clothes.