A strong core is essential for protecting your back and allows you to be overall stronger and able to attain a higher level of endurance. While increasing your core strength happens through working out, being able to actually 'see' a toned and defined core comes mostly from your nutritional habits...what you eat. If you have a layer of fat over your abs, you are not going to be able to see what is underneath...no matter how strong your core is!
In addition, extra pounds in your midsection increase your risk of cardiovascular and other diseases more than extra weight in your thighs and hips.
There are many diet plans that can help you lose body fat but unfortunately none have magic belly-flattening nutrients capable of melting away belly fat. "Spot-reducing" (or selecting which part of your body you lose fat from) just isn't possible. What will melt body fat, including belly fat, is lowering your overall body fat through a well-balanced, calorie-controlled eating plan.
Don't feel discouraged though, by making healthy lifestyle changes versus buying into the latest cleanse or nutrition bar, you will see longterm results versus short-lived de-bloating.
Your overall health plan should include strength training to preserve muscle mass, aerobic exercise to burn fat, and your diet should be healthy and calorie-controlled.