It's amazing that we all don't just float away on the gassy results of our bad eating habits.

Did you know that, even as you read this, there's about two-thirds of a cup of gas in your body and you'll expel about 10 times that much from various sources today? That's normal. Some of the gas gets out as belches, some of it as flatus (expelled rectally), some of it passes from your intestines into your bloodstream to exit via your lungs and mouth - one reason for bad breath if your digestion is upset.How well your body handles gas depends upon what and how you eat and the kind of a day you're having:

Perhaps you skipped breakfast and, well past lunchtime, in the middle of an important interview, your hungry stomach growls like a grizzly bear. There's nothing to do but put on your best, insouciant Miss Manners air and ignore it. And decide next time to eat breakfast.

So the next time you eat breakfast on the wing, gulping a doughnut and coffee or one of those egg-and-sausage-in-a-bicarbonated-biscuit numbers and, in an hour or so, you feel uncomfortably bloated. Later, you eat lunch at your desk, phone in one hand, fork in the other, talking and chewing at the same time. Forgetting your stomach's needs along with your manners, you are asking for a gassy, uncomfortable afternoon.

Tonight, you're entertaining the boss and his wife. It's going to be nerve-wracking. To calm yourself, you have a gin and tonic or something and soda, increasing the gas content of your stomach. You'll be talking a lot during the meal and swallowing air along with whatever your nervousness allows you to eat. To top off the evening, there will be liqueurs and coffee and cigarettes.

And heartburn.

Most of the above scenarios show how stress-plus-food increases the gas in your body.

"Eating on the go means you tend to eat a little faster and swallow more air," said Dr. Hugo Rams Jr., gastroenterologist and chief of the nutritional care committee at Doctors' Hospital, Coral Gables, Fla. "You may not be chewing your food as much as you should. Bigger particles in the stomach take longer to digest, giving the feeling of bloatedness that we all experience." Fatty foods are particularly troublesome because they are slow to digest, he said.

As for hunger, "when you hear those grumbling sounds, there is usually very little to do, except to realize that maybe it's time to eat," Rams said. "A midmorning or midafternoon snack of a granola bar or yogurt might be advantageous."

Some digestive upset feelings are not so minor, ranging from pressure in the abdomen to burning sensations or pain in the chest, which may mimic heart attack or gall bladder disease.

Real pain in the chest, especially a feeling of suffocating pressure, should not be passed off as indigestion. It might be the warning signal of a heart attack. Check it out with a doctor or emergency room.

"A burning sensation behind the chest wall usually suggests acid irritating the area," Rams said. That could be a backup (called reflux) of acid from the stomach and only a temporary discomfort. Retirees are particularly subject to this problem, according to gastroenterologists at the Cleveland Clinic, Florida. After years of rushing through lunch, the retiree tends to overeat at mealtime and take a nap afterward. Lying down forces caustic digestive acids to back up into the esophagus, irritating it and causing the burning sensation known as heartburn. It's better, the doctozs say, to take a leisurely walk or sit upright for at least an hour after a meal.

Bear medicines in mind, especially if you recently started taking a new one. Motrin, the big brother of Advil and several other over-the-counter pain treatments made from ibuprofen - can seriously irritate the esophagus. While simethicone, promoted in some antacids for its "bubble breaking" qualities, can help, antacids with bicarbonate of soda in them may make matters worse. Some sources recommend charcoal capsules for gas - but anyone taking a prescription drug, especially birth control pills, should check with a doctor before trying charcoal, which can deplete some drugs' effectiveness.

Clothes that are too tight - notably belts, pants, tight jeans and panty hose - contribute to heartburn, gas and other digestive problems. So does chewing gum - while the minty flavored kind may taste good after a meal, the chewing lets more air into your system, along with increased saliva. Puffy foods, souffles, anything whipped or fluffed to add more air and lightness, also send more air into the person eating it.

"Smoking has been shown to increase acid and induce reflux," says Rams. "We don't know how many cigarettes cause these problems, but we do know that patients with ulcers in the stomach and duodenum are very difficult to heal, despite therapy, when they keep on smoking. One study showed that decreasing smoking to below 10 cigarettes a day may be beneficial in terms of helping the ulcer to heal, but I would recommend stopping smoking."

Gas and heartburn can be troublesome in the later stages of pregnancy. Pressure on the stomach by the enlarged uterus, plus relaxation of the valve between the esophagus and stomach causes heartburn. Highly seasoned and/or gas-producing foods, such as beans, chili and cauliflower, are best avoided by pregnant women. So are meals before bedtime.

Anyone who is repeatedly troubled by heartburn should try cutting out milk, tomatoes, citrus fruits, fried foods and pizza. Over-the-counter antacids can help, but if the problem persists, see a doctor. Frequent heartburn can indicate hiatal hernia, a common condition in which the sphincter at the lower end of the esophagus has become weak, allowing the back flow of stomach acid and partially digested food.

Belching may seem to relieve indigestion - but it could, in fact, contribute to the gas problem. It can be a nervous habit, first swallowing air, then belching it back. Some of the air that enters the stomach stays there, forming a bubble that grows with each new belch-and-gasp action. To break the cycle, try to make a conscious effort not to belch.

Sometimes gas gets worse just when you think you are doing everything right. People who have been following medical advice to get more fiber into their diet often experience gas, bloating, pain and embarrassment.

Shop around and experiment with the types and quantities of high-fiber cereals and vegetables that you eat. If you are new to bran, for instance, give your body a little time to get used to it. Start with a small amount, say a teaspoonful a day, and increase it every few days until you reach the recommended dosage - usually the point at which constipation is relieved. Remember to drink plenty of water - six to eight cups a day - when taking bran.

Doctors' Hospital dietitians recommend fermented dairy products, such as buttermilk, yogurt and acidophilus milk to improve elimination. However, some people, especially the elderly, cannot tolerate dairy foods.