If you are vegetarian or vegan the chances are that many of your staple foods, particularly your usual protein sources, are high in FODMAPs. For example, legumes (beans) are high in galactans and many of your favourite veggies may also be off limits. So what can you eat?
Firstly, you don't need to cut out all FODMAP containing foods entirely. It's important to still eat a wide variety of foods to ensure you don't develop any nutritional deficiencies. Beans, lentils and soy products are an important source of iron, calcium and magnesium for vegans and vegetarians, as well as being a key protein source.If you are strict about avoiding other FODMAP sources, small quantities of beans and lentils may well be manageable. Try to spread out the amount you eat during the day so you don't overload your system. Soy products like tempeh and tofu should be ok to eat too as they are already fermented so won't need to be fermented by your gut.
There are also plenty of other vegetarian and vegan foods that are also fine to eat on the FODMAP diet plan. Grains should form the backbone of your diet: quinoa or amaranth are both excellent sources of protein. Oats, buckwheat and spelt can also contribute reasonable amounts. Nuts and seeds are ok in moderate portions - try using different nut butters to ring the changes. If you are vegetarian you can also eat eggs and lactose free dairy products.
If you do lots of exercise or are slim, you may struggle to get enough calories on the FODMAP diet when you start the plan. I'd recommend discussing with your dietician or nutritionist your own particular needs but you could try adding a rice protein supplement if you are althletic, just make sure that it is wheat-free and doesn't contain sweeteners or additives.