Can Lack Of Protein Intake Cause Tiredness?

I am 35 years old , weighing 73 kgs and height 5ft,10 in. , have eben having weight gain only around my waist area (almost 4 kilos in the last 1 year).I swim twice a week (i feel very tired through the day when i swim), and do some light exercises on the other days.On an average I can exercise 4 days a week , coz my job involves lot of travelling.I wanted to know 2 things (1) Is the tiredness has got anything to do with lack of Protein Intake? I am a noin vegetarian and eggs and chicken is a part of my diet. (2) do i need to incorporate more cardio exercises to keep my waistline in check.