According to professional trainer Michael James, sit-ups and crunches strengthen the abdominal muscles but do not create six-pack abs. These exercises increase strength and stamina but do not whittle fat from the midsection. The only way to achieve the six-pack look is to combine muscular exercises with aerobic activity and a reduced-calorie diet. Bodies that consume fewer calories than they expend burn fat for energy.
The best aerobic exercises that burn fat and reveal toned abdominal muscles are intense total-body exercises. Cross-country skiing and power walking are highly effective. Other people prefer to use rowing and elliptical machines. Running is also a strenuous aerobic activity, but it is a high-impact activity that puts great stress on the hips, knees and ankles.
Like all other muscles, the abdominals need time to recover from a workout. Intensive abdominal exercises lose their effectiveness when performed more than two to three times per week. Pushing the muscles past that limit slows their growth. Muscle & Fitness magazine recommends performing abdominal exercises at home on the same day as forearm and calf training.
Diet is just as important as exercise in an effective abdominal sculpting plan. Men's Health magazine recommends eating six small meals a day, spaced two hours apart. This keeps energy levels high and speeds up the body's metabolism, encouraging it to use food energy rather than storing it as fat. Men's Health encourages avoidance of fruit juices, carbonated soft drinks, beer and sugary sports beverages, as well as processed simple carbohydrates and high-fat meats.