I hope your getting a well balanced dinner. That's not much food for a whole day. Food is fuel for your body. If you don't get enough protein, the weight you lose will be muscle too. Losing muscle is bad because the more muscle you have the more calories you burn at rest (which is why men lose faster than women usually). Might be better to pack a cooler with some greek yogurt, a couple pieces of fruit, a small salad with chicken, etc. so that your body can get the nutrition it needs.