[time_to_smile]

You're making the implicit assumption that sugar substitutes do reduce the risk of being overweight. At least the first post I found on the topic suggest there is evidence of "a positive correlation between regular use of artificial sweetener and weight gain"[0]

0.https://www.publichealthpost.org/research/can-sugar-substitu...

[tuatoru]

This article suggests a mechanism for that positive correlation: impairment of glycaemic response by the most commonly used artificial sweeteners.