Good thing would be to stop demonizing foods... high fructose corn syrup is basically sugar. If you're not eating sugar or trying to cut it out of your diet, then sure, don't eat something that has high fructose corn syrup in it.
Grape Nuts? If you like 'em, eat 'em. All dieting is managing your intake of calories. If you can work a bowl of Grape Nuts into your calories for the day, go for it!
There aren't any foods - none - that are magic and going to make your body lose weight. Your brain, your ability to look at the bottom line on the food page of fitday.com, is going to be the best thing you use for a diet. Nothing else. Nothing.