Any Vegetarian or Vegan triathletes?

I eat a plant based diet.  You don't need as much protein as you think, and you don't need as much fat as you think.

What you do need is enough calories and energy to perform your workouts and recover. The reason you felt poor on the plant based diet (as many people who do it incorrectly do) is that you didn't eat enough.  By volume, you have to eat a whole lot more plants than chicken or salmon.  It isn't unusual for me to sit down and eat 2 lbs of potatoes (around 1000 calories). 

What you need to look at is percentage of diet from each macronutrient source.

I kind of shoot for 70% carbohydrates, 15% protein, 15% fat. 

Looking at what you wrote, I'd guess you're closer to 30-40% protein 30% fat 30-40% carbohydrate.  No wonder you fee heavy.

Example day for me:

Breakfast fruit smoothie:  4-5 bananas, 2-3 cups of berries, 8-12oz pineapple juice ~ 800-900 calories

Lunch: Starchy foods. So rice+beans or potatoes and vegetables.  800-1000 calories

Afternoon pre-workout meal:  Fruit juice, fruit, or similar   400 calories

Dinner: Another meal of starchy foods like rice+beans or potatoes and vegetables.  Also try to eat a green salad somewhere in here. ~ 800-1000 calories.

I train a lot, I'm male, and I'm larger than you which makes the calorie intake higher, but the premise is the same.  More simple sugars to bring up blood sugar to fuel the workouts or refill glycogen stores.  Starches to fuel the rest of the time.

Another key, my diet is VERY high in fiber. VERY.  When you eat a high fiber diet you have empty bowels which alleviates the "heavy full" feeling.  My transit time is around 12-14 hours.  High animal product diets tend to be low in fiber, and animal products take a long time to digest.  This means your bowels and intestines are simply full of more food.

Another benefit is that plant foods tend to be higher in water content.  As an athlete that never hurts.

This. That's why I can't eat salads at restaurants. There's just not enough to them. A whole bunch of iceberg and a few little tomatoes doesn't exactly fill you up, so my salads at home are dense on nuts and seeds, figs, beans, chick peas, hummus, things like that.

yeah, and you're eating salads for the nutrition in the greens, not for the calories.  You cannot eat enough lettuce to fuel your body, its impossible.

Dave said in his first reply that getting enough protein and fat isn't a problem, and he's right if you do it right, but IME it can be an issue, because many people don't understand how to do it.  Based on Dave's sample day above, he clearly does, so I'm sure it doesn't seem like an issue to him.  Notice how he combines grains and legumes (rice & beans) 2 of his meals?  That's because most plant sources of proteins do not contain complete proteins with all the amino acids found in animal sources.  It's necessary to combine like he is to get adequate amounts of complete proteins.  Another option is to eat more of the plants that provide complete proteins like quinoa.

There are no essential foods.  There are only essential nutrients.

YES! thank you for writing this out, I'm tired of explaining it all the time.  Our current culture is obsessed with protein.  Why? Because marketing people hype it up.  Why does everything say X grams of protein! If they wrote it on the package, it must be a big deal.

Eat your starches, eat your fruits, and eat your vegetables. It contains everything you need. (we can have a conversation about B12, but that's a fairly complex issue).

Hmmm...Interesting.  I've attended many nutrition sessions at personal training conferences with some of the country's leaders in the field, receive the Journal of Strength and Conditioning Research monthly, and this is the first time I've seen anything say it's been discredited.  The link you provided appears to be of a reputable source, and not a quack spouting pseudo-science, so I'll have to dig into it deeper and check the study references.  It's too lengthy for the amount of time I have available right now.  Thank you for sharing.

FWIW, I agree that many people have a misconception regarding the quantity of protein needed for a healthy diet.  I didn't mean to imply that it was necessary to shovel in huge quantities of protein.  Just that adequate quantities of protein (along with carbohydrates, fat, and a host of micronutrients) are essential to a healthy diet.  Any diet that eliminates entire types of food, such as vegan does, requires some consideration of where everything is going to come from.

Definitely true.  I'd also like to clarify that I eat a "plant based" diet, not vegan. around 99% of my calories come from plant sources.  I occasionally (maybe once a month) eat meat, almost never dairy.  I think humans are meant to eat some meat, just not nearly as much as most people do. Maybe once every week or two. 

Again, another discussion, but I can say this.  I perform, recover, and feel much better on my plant based diet, than I did on my old diet.