Go with the grain
Just because the bread's brown doesn't mean it's good for you. Check out the ingredient list. "Whole wheat" should be the first thing listed—not "refined grains," which have fewer nutrients and less fiber than their whole-grain counterparts. Also be sure the loaf has at least 3 grams of fiber per serving and doesn't contain any high-fructose corn syrup.
Raid the produce aisle
Pile on all the cucumbers, tomatoes, pickles, onions, bell peppers, or jalapeños you want. The extra calories they add to your meal are virtually nil.
All about meat
Ham: It'll only set you back around 60 calories yet packs 11 grams of protein. Select a nitrate-free variety, though (these preservatives have been shown to increase the risk of cancer when consumed over time). Less sodium means you'll also avoid that after-lunch bloat.
Turkey: The king of the healthy lunch meats. It's low in calories, fat, and sodium but loaded with protein. Buy 100% baked or smoked sliced turkey breast.
Roast Beef: Red meat gets a bad rap for being high in fat, but with many lower fat brands out there, you can now pile on the beef without adversely tipping the scale.
Hold the mayo
With an average of 100 calories and 11 grams of fat per tablespoon, there's nothing healthy about mayonnaise. Instead, dress your sandwich with these lighter options:
Mustard: The classic yellow variety contains zero calories or fat. For a bit more spice, go with dijon, which will only set you back 5 calories.
Relish: Good for more than just hot dogs, this pickled condiment is a delicious low-cal replacement for the mayo in a tuna salad sandwich.
Horseradish: Chefs have used this 3,000-year-old root for centuries, grinding it up and mixing it with vinegar to create a spicy sauce full of calcium and potassium. With only 6 calories per tablespoon, it tastes great with everything from roast beef to ham.
Dark green rocks
Iceberg lettuce contains virtually no calories— or healthy nutrients. Try darker colored greens like romaine and baby spinach. Each of them has roughly the same amount of calories but packs significantly more fiber, protein, and vitamins.
Always opt for the lower-fat cheeses (not fat-free, which taste terrible). For an extra boost of protein, go with low-fat Swiss, which has nearly twice the levels found in American or cheddar.