PACK IT COLD
It seems that — with just a few exceptions — almost all foods have to be kept cool to remain safe to eat. Get a well-insulated lunch bag and use an ice pack or freeze a water bottle, which can double as something to drink after it thaws.

EBags.com has great insulated coolers that are both stylish and convenient. The TechWeave ($19.95) keeps food cold for four to six hours, with proper ice packs, and profits from the pink version are donated to breast cancer research. Aladdin (www.aladdin-pmi.com) makes a Chill & Go series that has double-wall insulation to keep salads, fruit or other foods crisp and chilled.

Test your bag’s insulation with a refrigerator thermometer. The temperature should stay below 40 degrees Fahrenheit until lunch. Also, chill foods thoroughly before packing.

Sandwiches and Wraps
Chicken, turkey, lean cold cuts or low-fat cheese on 100 percent whole-wheat bread (whole grain must be the first ingredient) are all great options. Wraps, whole-wheat pita bread and tortillas (not fried) are also good, but always check the calories. A 1-ounce corn tortilla has about 70 calories. Avoid mayo, tartar sauce, creamy dressings and cheese. Use mustard, ketchup, salt, pepper or vinegar.

Pasta
Use whole wheat pasta, and add vegetables and a low-calorie sauce (50-60 calories per half cup). Pack it in a plastic container like GladWare or Tupperware. One cup of cooked whole-wheat spaghetti has 170 calories.

Salads
Buy prepackaged bags of salad and keep them in your cooler, then add your low-calorie dressing at lunchtime. Or get McDonald’s Newman’s Own Low Fat Balsamic Vinaigrette at only 40 calories per packet — you can buy them there at about 30 cents each (they’re not sold in stores). Avoid nuts, croutons, noodles and creamy salad dressings.

Chicken, Turkey and Sushi
All of these can be eaten cold. With chicken and turkey, opt for white meat and remove the skin, which has most of the fat. Sushi is sold in many supermarkets in plastic containers perfect for taking “to go.” Choose vegetable rolls (such as California or cucumber) to get fiber and flavor for fewer calories.

NO COOLING NECESSARY

Go Fish
If a cool pack isn’t an option, buy low-calorie single-serving cans or vacuum-packed pouches of tuna. Three ounces of white tuna packed in water (100 calories), with two pieces of whole-wheat bread (200 calories) and one packet of mayonnaise from a deli (100 calories) total 400 calories. Chicken of the Sea also recently started selling a 3-ounce vacuum-packed Smoked Pacific Salmon, which has only 120 calories.

PB&J
Peanut butter and jelly are among the few foods that require no cooling or heating. Though peanut butter is high in calories, using a moderate amount can keep your meal low-calorie and nutritious. Two tablespoons of natural peanut butter (190 calories), sugar-free jelly, such as Smucker’s (20 calories for 2 tablespoons), and two pieces of low-calorie, whole-wheat bread (120 calories) total just 330 calories.

Microwave, But No Fridge
A few companies make low-calorie microwaveable meals (although many are high in sodium). Some from Simply Asia (www.simplyasia.net) taste great, especially the Soy Ginger noodles at just 420 calories for the entire 8-ounce meal. The meals from Fantastic Foods (www.fantasticfoods.com) are organic and lower in sodium. They use an innovative cooking technology developed by NASA to preserve the flavor and nutrition. Try the Spanish Paella at only 280 calories for the entire 8-ounce meal or the 3-Bean Chili which is only 180 calories for the 8-ounce meal.

Meal-Replacement Shakes
They’re fine if you have one with a salad or soup and a piece of fruit. Make sure it’s satisfying so you don’t feel hungry too soon. Low-carb Slim-Fast has about 180 calories — taste test and find the ones you enjoy.

SOME LIKE IT HOT
To keep almost any food hot — especially soups, stews or chilies — Aladdin’s Heat & Go series has a double wall of foam insulation that’s activated in the microwave and can keep food hot for more than four hours. Thermos (www.thermos.com) and other companies also make insulated vacuum containers to keep liquids hot.

Soups
Hot (in an insulated container) or cold soups are great, especially since research shows that low-calorie soups (less than 120 calories for 8 ounces) are very filling and help you eat less. But soups can have a lot of sodium. Your best bets are those with less than 600mg per serving, such as Healthy Choice and the low-sodium versions of Progresso and Campbell’s. Also look for Moosewood’s excellent new line of low-calorie organic soups (www.fairfieldfarmkitchens.com).

Even if you just have hot water, there are low-calorie soups from Fantastic Foods and Health Valley to which you only need to add hot water (make sure to follow the directions, and don’t add too much).

SNACKS AND SIDES
Fruits and vegetables are low-cal, nutritious, filling and don’t have to be refrigerated or reheated. Apples, pears, grapes and cut-up melon are durable and portable. Enjoy unsweetened all-natural applesauce packs or a small box of raisins. Other good choices:

• Nonfat yogurt is a great portable snack, but it’s perishable, so pack it in an insulated bag or freeze it the night before.
• Low-calorie cereals (e.g., Puffed Kashi at only 70 calories per cup) work well in a sealable bag. Choose cereals with no more than 160 calories per cup, and avoid added sugar and partially hydrogenated oil.
• Hard-boiled eggs pack well, and you can either eat only the whites or go for the entire egg for about 80 calories.
• Whole-grain rice cakes vary widely in calorie and fat content. Quaker Lightly Salted Rice Cakes are only 35 calories each.
• Energy bars tend to be high in calories and fat but are an OK alternative to candy bars. One bar shouldn’t exceed 200 calories.
• Soy chips or baked chips come packed in 1-ounce portions. Look for brands with fewer than 120 calories per ounce (potato chips are about 160).
• JELL-O Sugar Free, Reduced Calorie Pudding Snacks are 60 calories and can be kept in a cooler until lunch.
• JELL-O Smoothie Snacks are 100 calories and great if you’re not a yogurt fan.
• Nabisco just came out with 100-calorie, portion-controlled snack packs (e.g., Oreo Thin Crisps, Wheat Thins Minis) that have no trans fat. They’re a decent snack once in a while, but don’t start choosing them instead of fruit.

CAMP OUT
A lot of interesting (but often high-sodium) on-the-go foods come from the camping and/or military crowd, who need tasty-yet-convenient chow. AlpineAire Foods (www.aa-foods.com) sells self-heating food packages: Pull a tab and in just 15 minutes the package actually cooks itself. The Chicken Pasta Parmesan (290 calories per 12-ounce portion, but more than 1,000mg of sodium) and the Meatless Mountain Chili (280 calories per 12 ounces, but more than 1,500mg sodium) are both very tasty and low in fat. They’re about $8 per meal, plus shipping.

BEVERAGES
Choose unsweetened iced tea, bottled water or other low- or no-calorie drinks. Try Crystal Light On the Go — pour a packet into any 16.9-ounce (0.5 liter) bottled water and shake. Avoid high-calorie sodas, fruit juices, teas or anything else with more than 30 calories per 8 ounces.