Having a big waist can be enough to convince you to buy a gym membership and get active. Provided your workout regimen includes enough cardio exercise and strength-training exercises such as crunches, you're likely to experience a shrinking waist, not a growing one. Crunches are a simple way to strengthen your abdominal muscles; within reason, they'll tighten the area, not increase your waist size.
Strong and Tight Midsection
In addition to working your abdominal muscles, crunches also strengthen your obliques, which are found on each side of your torso. Even if you perform crunches regularly to strengthen these muscles, it's unlikely you'll build them enough to result in a thicker waist.
Cardio and Crunches
Crunches won't play a significant role in shrinking your waist fat, however. Although muscle-strengthening workouts can elevate your metabolism, cardio exercise burns calories much faster. Provided you also cut down on your caloric intake, cardio exercise can help you turn a thick waist into a thin one. When you burn waist fat with cardio and tone your abs and obliques with crunches, you're likely to experience a thin, tight midsection.