Need Diet advice please..?

I am a 296 pound person. I went to a nutritionist last week and since then I have changed my diet to his opinion. I have currently started walking around the lake for 45 minutes after work because I cannot do much because I wear prosthetic legs. For breakfast I eat cereal or oatmeal. For lunch I eat brown rice, vegetables, beans and yogurt along with a handful of some pistachios or almonds. For dinner I have eaten a cup of brown rice , cup of vegetables or beans or on occasion some of amys organic frozen meals or maybe a veggy burger. As a late night snack maybe a weight watchers frozen treat or the baby bannanas dunked in dairy free chocolate bc he wants me to have a after dinner snack. I am not sure if this is wrong or should I be exercise after I eat also? The nutrionist who has his own book and much success with others I know pushes the 70% starch diet because the rest of the world eats similar. Please any advice helps.