If you are trying to lose weight, you are probably interested in sugar substitutes, also known as artificial sweeteners. Replacing sugar is a smart idea. Sugar has four calories per gram, and is a leading source of tooth decay. Many sugar substitutes have no calories, and still provide a sweet flavor for your food. Some, unfortunately, have unwanted side effects.

Research suggests that aspartame, for instance, sabotages weight loss. It breaks down into phenylalanine and methyl alcohol, which tend to make you hungrier. If you are trying to diet, you're already hungry. You don't need to be made even hungrier for no good reason. The phenylalanine also competes with dopamine and serotonin in your brain, which is bad, because dopamine and serotonin help you feel good. Their absence can leave you feeling depressed.

Now that aspartame is going generic, the makers of it have a new compound called neotame. It is a similar compound to aspartame, and may have similar side effects.

Sugar alcohols are a class of sweeteners that are neither sugars nor alcohols. Many sugar alcohols, such as maltitol, sorbitol, and mannitol, have what snack food manufacturers delicately call "a slight laxative effect." If you happen to be slightly constipated to begin with, this can be a good thing, but if you're not expecting to have to go to the restroom suddenly, it can be an unpleasant surprise. One sugar alcohol without this side effect is erythritol. It is three-fourths as sweet as sugar, has no calories, and no known side effects. Xylitol is as sweet as sugar, has no aftertaste, and has the advantage of being the one sugar substitute that is actively good for your teeth, as well as having antibacterial properties.

The sugar alcohols work by being indigestible. That is, they have calories, but your body is unable to absorb or make use of them. If human diets in the future contain large amounts of sugar alcohols, this may change.

One natural and calorie free sweetener is stevia, which is made from the leaves of a South American plant. While stevia cannot be sold in the US as a sweetener, it can be sold as an herbal supplement. Stevia unfortunately has a licorice-like aftertaste that many people find unpleasant. However, if you avoid using "artificial" flavorings, stevia is worth a try.

No sweetener is perfect. But many people have quite a sweet tooth, and few are willing to stay on a diet for very long when the food is unsatisfying. So, if using a sugar substitute keeps you from cheating, there are some good choices available to help you stick to your resolve.