Grazing can mean different things to different people. If by grazing you mean, eating small light amounts throughout the day rather than scheduling a couple of big heavy meals, then grazing is a good thing.
If, on the other hand, by grazing you mean, having alot of something pretty much all day long, then grazing poses a real problem.
The Weight Loss Journal has some suggestions that may help gently curtail the constant grazer's nibbling. Too hungry through the day? It may be that your diet is lacking and needs a little tweaking.
Got the right idea about small meals through the day but the wrong idea about what are good food choices? Veggies are always a healthy option. Chocolate cake is not.
"For example, instead of a candy bar, try low calorie string cheese. Instead of a bag of chips, have some crunchy vegetables. By making the right food choices when you're grazing, you'll have better luck at losing weight."
http://www.weightladder.com/is-grazing-a-good-idea