My first AWA...tell me where I am :-)

"People who use the artificial sweetener aspartame are better off consuming sugar, since aspartame can actually contribute to weight gain rather than weight loss. For example, high levels of aspartame have been shown to trigger a craving for food by depleting the brain of a chemical that registers satiety, or the sense of being full. Furthermore, studies suggest that sugars, if consumed after at least 45 minutes of continuous exercise, actually enhance the body's ability to burn fat. Consequently, those who drink aspartame-sweetened juices after exercise will also lose this calorie-burning benefit. Thus it appears that people consuming aspartame rather than sugar are unlikely to achieve their dietary goals."

The argument presented is making a number of critical assumptions which make it a flawed one. Primarily, when the argument presents aspartame to be a weight gainer compared to sugar due to the depletion of a chemical, it fails to acknowledge whether sugar will have similar chemical responses from the brain due to high levels. There is considerable lack of knowledge about the effects of sugar on the human brain which would have improved the evidence that aspartame is causing more harm. In order to make this reasoning better, the argument could talk about the aspartame harmful effect in direct comparison to sugar’s with ample scientific information.
Secondly, the argument mentions some studies about the beneficial effect of consuming sugar after exercise in the ability to burn fat. It does not take into consideration any beneficial effect of aspartame after exercise. Although it is mentioned that calorie burning might not be present, aspartame might provide vital other nutrients in addition to acting as a sugar substitute. The argument also fails to give better insight into the aspartame sweetened juices in regards to the health content. Any information mentioning about sugar’s effect if consumed before exercise is not discussed, which if practiced with aspartame may indeed prove more calorie burning.
Finally, the argument concludes that this aspartame is consumed instead of sugar to achieve some dietary goals. Dietary goals are a vague way of projecting the objectives of people. There may be people who want restricted weight gain with a use of sugar and thus consuming aspartame would obstruct their ambitions. Since there is no direct calorie comparison between the aspartame consuming population to the sugar consuming population, the actual ‘dietary goals’ is not imparting clarity to the reader.
Due to these logical fallacies in the argument, it is considered a weak claim.