Ummm... Sugars of all types are chemicals too, and aspartame is a pretty natural chemical as well. I generally don't use it (it isn't good for much and I don't drink soda), but it isn't tragically bad in a chemical sense. It has a very common metabolic pathway that many foods have. Nothing terribly dangerous there despite some of the handwringing.
Managing the glycemic index of the foods you eat is a very important factor in managing weight. Unfortunately, it is also unintuitive. There are many starch sources, such as potatoes, that are far more likely to make you gain weight gram for gram than sugar. At the same time, many of the sugar substitutes reduce the modest impact of sucrose on the glycemic index. Some such as aspartame pretty much evaporate (though you should not intake aspartame on an empty stomach; it messes with your blood chemistry a bit), though other ones achieve their effect through the relative intake reduction (I believe saccharine works this way). It is all a matter of knowing what foods have what impact on your glycemic index, which is one of the single most important components of losing weight. Fruit, for example, is not very good for you in this respect, especially things like apples and grapes, but I often see "dieting" women chow down on them.
I agree...although I generally use honey as a sweetening ingredient, I would use good old sugar before I even THINK of touching the artificial sweeteners referenced on this thread. The long-term consequences may not hit you until later in life. There are SAFER ways to lose weight.
