It's almost impossible to overlook the benefits of packing a lunch, whether the emphasis is on healthy eating, budgeting your paycheck, or saving time during a busy week. But packing the wrong thing can seriously derail your diet—at least for the day.

"The ONE thing to avoid would be any type of fluid with calories," said Atlanta dietitian Rachael Brandeis, MS, RD. "If you drink 150 calories from soda, sweet tea or any other sugar based beverage, you will not decrease your calorie intake from food by 150 calories."

Those empty calories would best be devoted to foods that satisfy cravings and give you energy.

"Liquid calories do not fill you up or add to the nutrient content of your lunch, said Brandeis. "They are purely excess calories that are stored."

The other big mistake many make when packing a lunch is that they don't pack enough food.

"In my practice, I see this all the time with clients who are trying to lose weight," said Braneis. "They skip breakfast, have something very small for lunch—a single food like a protein bar, shake, small salad or just fruit—and then they are ravenous as soon as they get home from work and consume all their calories in the evening."

If you're cutting things out, Brandeis said to keep fiber and protein, but eliminate the junk.

"Get rid of the empty calories that do nothing to fill you up," she said. "Put away the chips, sweets and sugary beverages and replace them with low fat flavored Greek yogurts, cottage cheese cups, seasonal fruits, salads and water."

Rachel Brandeis is a registered dietitian nutritionist with a private practice in Atlanta. For more about her work, visit her website at RachelRD.com

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