Yes, because fruits and vegetables contain high amounts of fiber. That means they will act like a laxative. I hope you aren't going to just eat only fruits and veggies or you might get the runs. I agree with adding protein, but you might want to add some complex carbs too. You don't need to go over board on the complex carbs or protein, but you do need them for balance....Aslo, some dairy would be nice too. The fruits and veggies highest in fiber are watermellon, apples, apple cider, (Don't confuse apple cider with apple juice.) broccoli, asparagus, raisins, and prunes.
If you eat just fruits and vegetables will you lose weight even if you completely binge on them?
It is not healthy to eat like this. Whether you are trying to lose weight or just maintain your health, you MUST eat a balanced diet with reasonable quantities of carbs, protein, and fat. While I am not an advocate of high protein diets, you really do need to be sure you are getting enough protein with each and every meal you eat.
I recommend that you eat 25-30% of your calories as protein. Here are some examples:
If you eat 2000 calories per day 500-600 of those calories should be high quality protein. That converts to 125-150 grams of protein per day. If you eat 3 meals and 2 snacks that translates to about 31-38 grams of protein per meal and 16-19 grams of protein per snack.
If you eat 1600 calories per day 400-480 of those calories should be high quality protein. That converts to 100-120 grams of protein per day. If you eat 3 meals and 2 snacks that translates to about 25-30 grams of protein per meal and 12-15 grams of protein per snack.
Protein does not need to be from fatty meat - there are plenty of lean meats readily available, not to mention fish, seafood, and poultry. Also, LF cottage cheese and soy nuts are great sources of protein. I personally do not recommend nuts or peanut butter because they are higher in fat and tend not to be all that filling.
It is also important that you eat the correct amount of calories based on your body size, age, gender, and activity level.