What is a good breakfast cereal to have when trying to lose weight?

Oatmeal. Old fashion oats are a good choice. A half cup (dry) serving has 150 calories, 4 grams of fiber (helps fill you up), 5 grams of protein (helps keep you feeling full) and only 1 gram of sugar. You might want to add additional protein like egg whites (20 calories and 5 grams of protein/per egg white). Having protein at breakfast and with every meal helps keep you feeling full longer.
High fiber & fruits. Eating breakfast helps you lose weight. But not just any breakfast. A healthy, high fiber breakfast with plenty of fruit and whole grains is best.