Bariatric surgery is the beginning of a new life for the morbidly obese. Surgically shrinking the stomach kick starts weight loss, often resulting in 70, 80, 90, 100 pounds of more being shed in less than year.

The wonderful discovery you are likely to make after bariatric surgery is that bariatric methods can cure obesity when nothing else works. But even after bariatric surgery - in fact, especially after bariatric surgery - you will have to be careful about what you eat.

Whether you have had a lap band, stomach stapling, or Roux-en-Y bypass, after bariatric surgery your new stomach will only hold about a half cup of food. The bad news is, this only about the amount of food you can place loosely on a coffee saucer.

The good news is, even this small amount of food will now leave you as full as if you had eaten a whole pizza. Or maybe even two.

And now that you can eat very little, after bariatric surgery it's especially important that you make wise food choices

After bariatric surgery, gastric bypass patients, especially those who have had the Roux-en-Y procedure, must avoid concentrated sugars and sweets

Part of the reason for this prohibition is, there is no faster or surer way to regain the pounds you've lost than to start making dessert your entire meal. Also, even if you are not diabetic, sugar can make you sick.

Foods made mostly of sugar can trigger a phenomenon known as dumping syndrome. The stomach does not have to break down sugar, so it goes quickly to the small intestine.

The ensuing "sugar rush" can make you nauseated. It can cause you to vomit. You may even pass out. Eventually you may develop a tolerance for sweets, but it's about equally likely that you may not.

Even if you can't eat sweets, however, you still have to eat. Most people with gastric bypass have to plan ahead to have that small quantity of healthy food they are able to eat in every meal.

If you don't have food close at hand, and you get hungry, there's an added risk you'll reach for whatever food is available. The snack foods and fast foods that easiest to obtain are exactly the foods you have had the surgery to avoid.

You will probably have to rely on supplements to get all the nutrients you need.

Your newly resized stomach does not absorb folic acid, vitamin B12, folic acid, calcium, or iron in quantities sufficient for your body's needs. You shouldn't even try to get these nutrients from food. It's best to take nutritional supplements, preferably liquid varieties.

Even though you do have to avoid sweets, it's OK eat foods you're familiar with and like. Vomiting, nausea, and diarrhea can be caused by eating new foods; you may also develop sensitivity to milk, meat, or fiber. If stomach upset occurs, wait a few days before trying a new food again.

Avoiding dehydration is a key concern when you have diarrhea. You can prevent dehydration by drinking water between meals, but remember, your stomach can only hold half a cup (about 125 ml) at a time.

Finally, keep in mind that even after bariatric surgery, overeating is still possible. Your stomach gradually expands after surgery. Portion control (keeping portions small) will help you lose all the pounds you need to lose and keep them off.

Even after bariatric surgery, lifetime diet and exercise are still necessary. But successful gastric bypass surgery can give you the boost you need to regain control of your life and become truly, lastingly, healthily thin.