零度可乐喝多了反而会增肥(2)

While the review focused on artificial sugar substitutes (such as aspartame and saccharin), it casts doubt on “natural” sugar replacements like stevia—which is derived from a plant—and the sugar alcohol erythritol, which are often advertised as magical replacements able to recreate sugar's taste without recreating its detrimental consequences on health.

As with artificial sweeteners, some of this concern arises from how little we know about these replacements’ long-term effects on the body. Researchers have suggested they could interfere with gut bacteria and the body’s ability to process sugar, although these theories are unconfirmed.

It also has to do with habit building. A number of companies that use sugar replacements market themselves as “healthy” versions of junk food. One of the most prominent is the low-calorie ice cream brand Halo Top. A pint of its chocolate ice cream contains 280 calories, versus the roughly 1,040 in a pint of chocolate Haagen Daz. To achieve this discrepancy, Halo Top uses both stevia and erythritol to cut back on the amount of sugar in its recipe.

Halo’s advertising leans heavily on the idea that its products are good for you—so good for you, in fact, that it’s fine, encouraged even, to eat an entire pint in one sitting. (“Save the bowl, you’re going to want the whole pint,” its website reads, while Halo pint lids come emblazoned with the command to “stop when you get to the bottom.”) Halo Top did not respond to a request for comment.

Nutritionists worry that this type of messaging, instead of helping those trying to lose weight, encourages unhealthy eating habits that lead to weight gain. Products like Halo, on one hand “can be seen as a form of harm reduction,” says Sharon Akabas, the associate director of the Institute of Human Nutrition at Columbia University. “On the other hand they benefit from being a 'healthy halo' -- no pun intended. People forget they are still mostly a junk food. Products like these blur boundaries.”

Marion Nestle, a professor of nutrition, food studies, and public health at New York University, concurs. “A better approach might be smaller portions of the real stuff," she tells Fortune in an email.

The review on artificial sweetener serves as a good (if frustrating) reminder that when it comes to weight loss, there are few, if any, shortcuts.