Well, if all the sensible methods fail (exercise, smaller meals, healthier foods etc.) fail, you can always go for the short term gain method used my Marilyn Monroe, enemas and more enemas.
Personally, find out which foods make you fat as it varies from person to person and completely cut those out, anything that makes you feel bloated after you eat it would be a clue that it could be one of those foods and definitely reduce refined sugar and refined wheat products in your diet. Also cut of snacking between meals, eat very slow so your stomach has time to recognize when it is filled sooner and eat until you reach the 'not hungry level' and stop, never stuff yourself.
You can also raise your metabolism which will help you lose weight by eating many small healthy meals instead of the average 3-4 larger daily ones. Eat something healthy and small every 3 hours or so and do not exceed your daily calorie intake level.
Many people do not think it is necessary, but I am also an advocate of exercising at the gym.