Focus on the Fish - Eating mainly salmon, tuna and other fish will fill you up with healthy omega-3 fatty acids which have numerous benefits including hearth health, improved skin, joint health and reduced cravings.
Minimise the Rice - This follows on from the above point, if you stick to Sashimi (raw fish) you will be much better off. Too much rice will raise your blood sugar, and increase the chances of holding extra weight. If you have to eat some rice, then have a small portion of it with raw fish.
Have More Wasabi - Wasabi acts as a thermogenic, it heats up the body similar to chilli. Wasabi is made from horseradish, which also assists with digestion, speeding up metabolism, in turning burning more calories and assisting with weight loss.
Add Ginger to your fish - Ginger is fantastic for digestion. Healthy digestion leads to more energy and less cravings, to adding ginger to your sushi will give you more energy to burn off those calories and reduce bloating.
Not too much Soy Sauce - Soy Sauce contains a lot of sodium, which holds excess water. Although it won't put on weight directly, having too much soy sauce will cause you to look bloated and give you the impression that you have put on weight.
Avoid the fried stuff and the sauces - deep fried anything is bad for you. Try and stick to the fresh raw sushi and you'll walk out of the sushi train bouncing off the walls rather then slumped over trying to digest all the bad fats they use to deep fry and sugars in the sauces and mayo.