After reviewing the search results, there is no clear information about the details, positive or negative effects, or ingredients of any weight loss product used by Christina Aguilera. Some of the search results mention keto pills, prescription diet pills, and weight loss supplements, but there is no evidence that Christina Aguilera used any of these products.

One article mentions that Christina followed a low-calorie diet called the rainbow diet, which involved eating brightly colored fruits and vegetables every day. However, there is no information about any specific weight loss product used by her.

In summary, there is no clear information about any weight loss product used by Christina Aguilera, and it is important to be cautious when considering any weight loss product or supplement. It is always recommended to consult with a healthcare professional before starting any new diet or supplement regimen.