Tweetyさんに教えていただきましたので取り上げてみました（＾＾； > 当該エントリー コメント
アメリカでダイエットソーダ（ダイエットコーク/ペプシ等）を飲まない群、1日1本飲む群、2本以上飲む群で比較すると、後者になるほど太り易いという研究結果が発表されたようです。
もちろんダイエットソーダにカロリーはありませんので、それ自身で太るということはありません。ただ、推測される理由として、ダイエットソーダの「甘さ」で舌を満足させて騙すことはできても、糖分が行く脳を騙すことは出来ないため、糖分（やカロリー）をより求めてしまうことがあるのではないか、と推測しています。
また別の研究として、人工甘味料入りのドリンクを食事前に飲むと、人工甘味料入りの飲まない場合と比較して、食事により多くの高カロリーのものを求める傾向が出ているとのことです。
以前Ⅱ型糖尿病患者に対する研究として、糖分入りの飲料を飲む場合、フルーツジュースの役割について疑問を持つ方もあったようですが（体重増を招かない）、この結果はそれに関連するのではないかと示唆しています。フルーツジュースは自然の糖分ですしね。（砂糖や果糖ぶどう糖液糖とは違って）
引用元：Houston Cronicle 6/11
Diet drinks won’t provide shield from extra pounds
A study shows sodas in general increase the odds of gaining weight in middle age
A Diet Coke, Pepsi, Dr Pepper, Sprite or any other zero-calorie drink won’t make you fat, but a new study by San Antonio researchers suggests that drinking diet soda in middle age dramatically increases the chance of gaining weight later.
The study of more than 600 normal-weight people found, eight years later, that they were 65 percent more likely to be overweight if they drank one diet soda a day than if they drank none. And if they drank two or more diet sodas a day, they were even more likely to become overweight or obese.
And more surprising still, those who drank diet soda had a greater chance at becoming overweight than did those who drank regular, full-calorie soda.
"I want to be very clear," said the study’s lead author, Sharon Fowler, an associate faculty member at The University of Texas Health Science Center at San Antonio, "Our findings do not prove that diet soft drinks cause people to gain weight.
" Right now we don’t have any clear public message here. This just raises an interesting question."
Looking for explanation
Fowler presented the study’s results Sunday in San Antonio at the annual scientific meeting of the American Diabetes Association.
By itself diet soda cannot cause weight gain, scientists say. The "zero calories" tag on the label really does mean 0 calories, so diet drinks do not increase the amount of energy the body must burn a day to gain or lose weight.
The effect shown by the study in the San Antonio Heart Study ・age 25 to 64 when they first enrolled ・must be explained by other means.
One possibility: A person who drinks a diet soda may feel it’s OK to make up for those calories with another high-calorie food.
"If I use a diet soda as an excuse to eat more, like a monster burger, then it’s my fault if I gain weight, not the diet soda’s," said John Foreyt, a Baylor College of Medicine obesity researcher.
That’s probably one factor, Fowler said. Another may be that, while the tongue is temporarily satisfied by the sweet taste of a diet soda, the brain isn’t similarly fooled. It still wants calories for energy. Other studies have suggested that people who drink an artificially sweetened beverage before a meal will eat more high-calorie foods than those who do not.
A blurred debate
An analyst for a food industry group, the Center for Consumer Freedom, said the hype surrounding obesity has blurred the debate over fat.
"It doesn’t take a rocket scientist to realize that people who are worried about their weight, people who are gaining weight, might choose to drink diet soda," Dan Mindus said. "They call it diet soda for a reason. Choosing a zero-calorie drink when you’re worried about your weight is just common sense."
Fowler said she was particularly struck by the finding that the risk for becoming overweight and obese steadily increased with the amount of diet soda consumed. She said that suggests to her the effect is real, and not an error in reading data.
The new research clouds an already muddy picture of weight gain and beverages.
Last year, a study linked sugar-sweetened beverages to weight gain and type 2 diabetes. And some dietitians have also questioned the role of fruit juice, which is often high in natural sugars and calories.
This leaves one drink that everyone agrees is healthy and won’t increase the risk of gaining weight. It’s also the cheapest beverage, if you don’t mind drinking it from the faucet.