Strong abdominals don't always equate to a skinny midsection. Crunches, along with other abdominal exercises, build endurance and power in your belly muscles, but do little to reduce the fat that surrounds them. To lose belly fat, you need to do total-body cardio exercise that burns calories so you use stored fat.
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Belly Fat Makeup
Belly fat is composed of subcutaneous fat, which is pinchable and lays just under the skin, and visceral fat, which exists deep inside the trunk and surrounds your internal organs.
Neither type of fat is particularly desirable, but visceral fat is especially insidious, as it releases compounds that increase inflammation and contribute to a higher risk of disease, including cardiovascular conditions, type 2 diabetes and some cancers.
Fat Burning 101
Belly fat is a storage depot for excess calories. You store fat in fat cells throughout your body in the form of triglycerides. Where these fat cells predominantly accumulate, whether it's the belly, the thighs, the arms or elsewhere, depend on genetics and hormones.
When you burn more calories than you consume, your body converts these triglycerides into usable energy to be burned for fuel. Just like you can't decide where fat accumulates, you also cannot dictate from where your body mobilizes this fat, however.
That's dependent on genetics — but when you burn enough calories and don't replace them, you'll eventually lose belly fat. Visceral fat is some of the first fat to go as it's metabolically active; subcutaneous fat can be more stubborn.
The Role of Crunches in Fat Loss
Because your body has to go through a complex process of converting triglycerides to energy and then burning it, you can't target a specific area for loss. Although crunches help build muscle, they don't burn a lot of calories. It's nearly impossible to lose weight or belly fat using crunches alone.
This doesn't mean you should banish all abdominal exercises from your fat loss plan — when you do drop belly fat, you'll reveal strong, taut muscles. To lose the bulk of your weight, though, participate in cardiovascular exercise such as jogging or hiking, as well as total-body strength-training.
The cardio helps you burn extra calories and convert fat into fuel. The strength-training builds muscle, which burns more calories when your body is at rest than fat tissue.
Make a Plan
Along with training your back, thighs, glutes, chest, arms and shoulders, include crunches and other ab-strengthening moves such as planks, bicycle crunches and stability ball knee tucks.
Aim for at least two total-body strength-training sessions per week. To lose significant weight, particularly from your midsection, go for at least 250 minutes of cardio per week. Work at a moderate intensity as you walk briskly, dance or cycle.