If you are a pesco vegetarian you can lose and maintain your weight easily as you can have fish and other sea animals along with your normal diet.So Fish is the best source of omega 3 fatty acids.It contains less than 5% of fat. They helps in boosting the immune system. Some varieties of fish have high levels of Vitamin A, C, D, and E, which all have antioxidant properties. Seafood has very little cholesterol,but some exception are there like prawn,shrimp and squid,which you should avoid.