The Top 5 Benefits of Wearing a Waist Trainer A waist trainer is a garment that is worn around the waist to help cinch in the midsection and create a more slender, hourglass-shaped figure. There are many benefits to wearing a waist trainer, including weight loss, improved posture, enhanced workouts, a more slender waistline, and the ability to be worn discreetly under clothing. If you're considering trying a waist trainer, keep these benefits in mind and see how it can help you achieve your fitness goals.