Do artificial sweetners make you fat?

In another thread Sleel posted this data about artificial sweeteners, with appropriate links.

I was like, whoa! Is this actually true? I read the links which all seem to go back to the same experiment. So, has this been confirmed or is there other data on this phenomenon showing the artificial sweeteners don’t help you lose weight, but may even cause you to gain more. I am really curious.

The jury’s still out; most of these explanations have a lot of “may” and “perhaps” and “could” in them, and they’re basically side observations of experiments that were looking for other things or were done in other species.

To really answer this for sure will take studies designed to actually test it; which so far as I know haven’t been done yet.

But, hyperbolic public news stories aside, I doubt it. Weight loss studies from the early 80’s often showed that switching from sugared to diet cola was one of the biggest changes you could make to increase weight loss. Recent studiesin humans (not rats) show similar results. And from a strictly medical standpoint, it’s hard to imagine that an insulin response, however strong, would result in the consumption of more calories than the 150 or so saved by not drinking sugared pop.

I no longer have access to the content, but there’s a PubMed review study of many weight gain studies here. Their general takaway (someone please confirm) is that the evidence is fairly strong that diet drinks decrease weight gain, as you’d expect.

The single most-quoted study is the most suspicious, in which while studying something else, it was noticed that the diet soda drinkers gained more weight. This is a classic reversal of cause and effect (aside from some who prefer the taste, most folks only drink diet pop if they have weight control issues), and probably doesn’t indicate anything: the controls were not designed to control for the result that the everyday media reported.

In other words, “gee we observed something odd”, but no real testing to specifically support on deny the hypothesis, especially on humans. I thought it was a bit counter-intuitive, but thought I’d ask.

A few additional studies, some old:

Women who uses artificial sweeteners gain more than those who do not.


Bottom line seems to be that it is better than a sugar or corn syrup beverage but maybe not by much.

They certainly cannot cause you to gain weight just by themselves. If you drank nothing but diet soda all day every day you would lose a ton of weight and die of starvation (they have 0 calories per serving.)

A lot of people who switch to diet sodas do so because of things like a diabetes diagnosis or a desire to lose weight. So by the very nature of the beast a lot of the people who drink diet sodas probably have weight control issues. Most people that are trying to diet are “bad dieters” and may naturally and subconsciously consume more food when they switch to diet sodas because they go from drinking 8 coca-colas a day to drinking 8 diet cokes and they start to think they can go wild with the feed bag.

The speculation is that it is a bit more subtle than that -

The body responds to the sweet taste in a Pavlovian fashion: the bell rings and the response occurs. In this case the sweet taste triggers an insulin response without an actual blood glucose spike to deal with that lowers blood sugar which triggers more eating of more energy dense foods over the next short period of time.

A recent review demonstrates that the association is well established but causation is still a matter of speculation (and extrapolation from animal studies):

An association. How strong I guess is the question. And what is the actual cause behind it, if it is true. Sounds like it needs more study. However, if one we to go to McDonalds (for example) and get the same exact meal every day for a month with a regular coke and the next month the same thing with a diet coke, presumably, he would not gain the same amount of weight the 2nd month or might actually lose weight. If all other factors were equal (no extra snacks because you had a diet soda). It is just straight calories at that point.

It seems like the question is, does it cause the body to respond in some way which would increase the body’s desire for more calories? And that we don’t really know for sure yet.

I would venture to say that someone eating at McDonald’s every day for month is going to gain weight either way.


Sleel was correct in disputing that diet soda is “by its very nature skinny”. It isn’t.

The evidence, such as it is, falsifies the proposition that use of artificially sweetened beverages in real world circumstances will help a person lose weight and is consistent with the proposition that it causes weight gain.

That is not an endorsement of sweetened beverages.