I have lost and gained weight through fad diets, crazy workouts and probably anything I read would help. But the weight crept back since I love eating (and that is not an understatement!). What finally helped me lose 40+ pounds and keep it off was increasing my protein intake and strength training and weights.
Let me start with the misconception of 'belly reduction':
There is no such thing as 'Spot Reduction', you cannot focus on one part of your body and lose fat from that area. Your body burns fat throughout when you workout- and usually belly fat is the most stubborn to get rid of. There are various reasons for that-lifestyle, hormones (especially in women), Insulin (sensitivity to sugar), aging etc. Also, some studies suggest that there are different kinds of fat cells in our body that react differently to calorie reduction- if you want to read more about it- The Simple Science of Losing Belly Fat…For Good.
However, if you are lean all over and have trouble only at the belly area, you might want to try to 'tone' that area- gain muscle that makes your abdomen look tight while focusing on your diet. Diet plays a very important role in losing and maintaining belly fat (that is why you see really thin people with some fat in that area). One very important advice from my own experience is DO NOT STARVE- I repeat DO NOT STARVE YOURSELF! It is probably the worst thing you could do and is in fact counterproductive. If you do not eat, your body will go into starvation mode and start holding on to the fat in your body. It will wreak havoc on your metabolic system and whatever food you do eat, will quickly get stored because your body thinks "OMG calories! I need to store this for when you starve again!" Eat, but eat smart. You need to eat a lot of protein in order to gain muscle- the more muscle you have, the more your body will burn calories even when you are resting (and you can eat more- win win!). Eat a balanced diet and exercise, the best exercises for lazy people are planks and crunches, although push-ups help your overall body a lot. Some cardio will go a long way in tandem with the diet and strength training and in no time, you will start seeing results.
Good Luck and trust me, this age-old slow method works faster than fads and is one sure shot way of achieving those envious abs.