Is it time to ditch diet soda? The California-based group U.S. Right to Know thinks so. It's petitioned the Federal Trade Commission to prohibit Coca-Cola and Pepsi from using the word "diet" on the labels of soda containing zero-calorie artificial sweeteners, calling it "deceptive, false, misleading, fraudulent and harmful."

Consumers who wish to lose weight may actually suffer physical harm in that these products may lead them to gain weight instead of losing it, the group noted. They asked the FTC and the U.S. Food and Drug Administration to investigate the use of the word "diet" by other soda manufacturers, too.

We think they're onto something – especially in the wake of a brand-new study linking diet soda sipping with a tripled increase in belly fat in older adults. It's the latest in a series of studies finding that the drinks soda-lovers reach for to cut calories are letting them down. Grab an unsweetened iced tea and read on.

A wider waistline: The waistlines of daily diet-soda drinkers expanded 3 inches over nine years in a recent University of Texas study, while non-drinkers' middles enlarged by less than 1 inch. Even occasional users had wider middles: They gained 1.8 inches – enough to make your favorite pants, skirt or dress too tight. It's more than a fashion problem. An expanding waistline is a sign that you're putting on more visceral fat, the deep belly fat that wraps around internal organs and even builds up in your liver, raising risk for heart disease and diabetes.

All-over weight gain: When the same researchers looked at weight among diet-soda drinkers and abstainers, they found a surprising connection. People with a serious diet-soda habit (they drank at least three servings a day) were twice as likely to be overweight or obese as people who skip soda. Over seven to eight years, diet soda sippers gained an average of 1.5 more pounds than soda-skippers, too.

A fluke? Not at all. An American Cancer Society study that tracked 78,694 women for a year found that diet-soda drinkers gained nearly two pounds more than non-users.

What's going on? It's easy to chalk it up to "magical calorie math" – thinking it's OK to grab a second slice of pizza because you're saving calories with a diet soda. But new research suggests that artificial sweeteners in soda (and probably in other foods, too) are backfiring in much deeper ways that rev up appetite and alter metabolism. So here's the skinny about diet soda's worse-than-ever downsides.

Messed-up metabolism in your brain and digestive system: Artificial sweeteners may increase appetite by giving the brain a taste of something sweet without delivering the calories that would dial back hunger and cravings, lab studies suggest. A recent study from Israel's Weizmann Institute of Science found that artificial sweeteners may interfere with intestinal bacteria in ways that boost risk for prediabetes and diabetes.

Higher risk for health problems: Three other studies found that even one diet soda a day boosts odds for developing metabolic syndrome – a precursor to diabetes and heart disease – by 34 to 44 percent. And yet another study found that a daily diet soda habit increased the risk for Type 2 diabetes by a whopping 67 percent! No wonder a Purdue University neuroscientist who's looked into diet soda's effects told Time magazine recently, "Right now, the data indicate that over the long term, people who drink even one diet soda a day are at higher risk for adverse health outcomes that they are probably drinking diet sodas to try to avoid, like Type 2 diabetes, metabolic syndrome, hypertension and stroke."

The solution? Sip smarter. Choose naturally low-cal drinks, like unsweetened tea or coffee (hot or iced), or water or club soda flavored with lemon, lime or even a slice of cucumber or a strawberry (yum!) It's easier than you think.

Mehmet Oz, M.D. is host of "The Dr. Oz Show," and Mike Roizen, M.D. is Chief Wellness Officer and Chair of Wellness Institute at Cleveland Clinic. To live your healthiest, tune into "The Dr. Oz Show" or visit (c) 2015 Michael Roizen, M.D. and Mehmet Oz, M.D. Distributed by King Features Syndicate, Inc.

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