Ask the Dietitian: The Case Against Diet Soda

Sidney Fry, MS, RD
by Sidney Fry, MS, RD
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Ask the Dietitian: The Case Against Diet Soda

We’re back with yet more of your questions about nutrition, weight loss and more. This week’s edition centers on a polarizing topic: sugar and artificial sweeteners. Read on!

As it turns out, America’s favorite diet sodas might not be so diet-friendly. Quite the opposite, in fact: More and more research is finding artificial sweeteners (most commonly found in diet sodas, but also a variety of other lower-calorie and lower-sugar processed foods) aren’t the magic liquid weight-loss trick they were advertised to be.

A 2015 study, published in the Journal of the American Geriatrics Society, found that over the course of nine years, diet soda drinkers gained almost triple the amount of abdominal fat over non-imbibers. Abdominal fat — or “visceral fat” — is the more harmful type that surrounds organs and is a known risk factor for heart disease, diabetes and metabolic syndrome. According to the study, the more diet soda subjects consumed, the greater the risk.

While scientists are still hard at work trying to identify the exact mechanism by which artificial sweeteners may cause weight gain, we do know this: They’re 200–600 times sweeter than sugar. But unlike sugar, they don’t satisfy the appetite with calories, causing some people to compensate by eating more later in the day. A 2014 study by the Johns Hopkins School of Public Health found that in a sample of nearly 24,000 subjects, diet soda drinkers consumed more calories from food than their full-sugar-soda drinking peers.

Some people argue it’s not so much the diet soda that causes weight gain, but that habitual diet soda drinkers tend to be less healthy overall. Whatever the case, artificial sweeteners are just that — they’re artificial. And they’re found in products that are highly processed and often contain artificial flavors and colors, too. Stick to wholesome, hearty foods and satisfy your sweet tooth with foods high in naturally occurring sugar like fruit and dairy, that also come packaged with fiber, protein, calcium and other beneficial nutrients.


Short answer: not exactly. But there’s an easy way to calculate calories from sugar on your own. On food labels, sugars are listed as a subset of total carbohydrates. One gram of sugar has about 4 calories. To find calories from sugar, simply multiply the number of sugars grams by 4 to get the number of calories from sugar. A 12-ounce soda, for example, has 140 calories and 36g of sugar. Do the math, and you’ll discover rather quickly that all of the calories in a soda come from sugar.

But, before you go writing off all foods that contain a significant percentage of total calories from sugar, it’s important to understand that there are two categories of sugar in food: those occurring naturally (like fructose in fruit and lactose in milk) and those that are added during processing (in the form of honey, high-fructose corn syrup, granulated sugar, fruit juice concentrate and a laundry list of other names).

For example: Plain whole-milk yogurt has about 11 grams of sugar per cup, but all of it comes naturally. Vanilla (and almost any other flavored variety) whole-milk yogurt has more than double that amount — half naturally in the form of lactose, and the other half added during processing to add flavor (and sweetness).

So how can you tell the difference? The problem is food manufacturers aren’t currently required to list added sugars on labels — only the total sugars. The FDA has issued a mandate that will eventually require all food companies to list added sugars as a subset of the total, but the original compliance deadline of July, 2018, has been extended until further notice.

Until then, read the ingredient list. If any sugar is listed as the first or second ingredient, chances are most of the calories in your food comes from added sugars. Buy unsweetened or plain varieties when available, and add naturally sweet fruits, sweeteners and foods in your own kitchen so you know exactly how much you’re getting.

Got more questions for me? Keep ’em coming! Ask away in the comment section below, and keep up with the MyFitnessPal Facebook page for more opportunities to Ask the Dietitian.

About the Author

Sidney Fry, MS, RD
Sidney Fry, MS, RD

Sidney is a two-time James Beard Award-winning food and nutrition writer, editor and mom based out of Birmingham, Alabama. A registered dietitian with a passion for research and being proactive about health, she loves to eat, write, run and create simple, tasty meals with whole-food-based approach. Find out more from her website, Instagram or Twitter.


12 responses to “Ask the Dietitian: The Case Against Diet Soda”

  1. Avatar Toularz says:

    This makes me sad… diet Pepsi is my go to drink.. I love it So much. So when it comes to drinking something satisfying what any I suppose to do? I can’t drink ONLY water. I’ll go crazy. Help. 🙁 -Danielle

  2. Avatar Svix says:

    There’s a few problems with this article, comments like ‘They’re 200–600 times sweeter than sugar’ may be true but is that relevant at all? Much fewer quantities will be used than sugar because of this so what is the point here?

    The most misleading point you make is ‘diet soda drinkers consumed more calories from food than their full-sugar-soda drinking peers.’ Maybe this is because diet drinks provide less energy (calories) so the extra food is to compensate for the defecit? This statement would still hold true if diet soda drinkers ate more food but still at a lower overall calorie intake than less food with a full sugar drink. That gives an entirely different tone to the argument!

    For an ‘award winning’ MS RD nutritional consultant I would expect much more rigor in presenting this.

    • Avatar Elle Jae says:

      How many overweight people have you seen order an extra large value meal with a diet soda? Plenty, I think she makes a valid point. The study is what the study is, it’s not an argument.

      • Avatar Svix says:

        I doubt the diet soda is making them eat a huge amount more though, it’s probably just an easy way to feel like they’re making a healthy choice. The age old correlation doesn’t equal causation. I don’t have a big problem with the study, just the way this article is presented.

    • Avatar SquidLord says:

      It’s been a hot minute since I last read up on this.. But I *believe* it has a lot to do with your brain. Your brain expects the calories due to the very sweet taste. The calories never come, so your poor brain unleashes a rush of ghrelin (the hunger hormone) so you get hungry. On top of that, you’re “behaving” and eating nicely so you can just go ahead and have that extra snack…or 3. Don’t quote me but I think that’s what the current thinking is.

  3. Avatar Chris says:

    Who even said soda is good for you?
    It’s not, but we still drink it regardless. So in my opinion, drink soda in moderation.
    I normally only have one diet soda a day, if that. Other times when I have a sweet attack, I go for a diet mt dew cause it’s sweet to me, and no where near all the junk that’s in high end sweets.
    There’s lots of junk out there bad for us, but we’re gonna eat it or drink it anyway. So just consume it in healthy moderation.

  4. Avatar fab says:

    The study was conducted with >65 year old people so it is unrelevant for most of the readers here

  5. Avatar ClippityBob says:

    How many times does this SAME study with bad data have to be rehearsed to make it true? I have heard it said that, “I stopped drinking soda and lost 62,000 pounds overnight”. Of course it’s not true. I have drank diet soda for years and am healthier than anyone I know(by the doctor’s numbers, not my estimate). I work out rarely, feel great every day, NEVER order a large(or extra large) anything. I even drank 1 gallon of just water per day for months and lost not a single pound, or felt any better or different. When the coroner starts listing artificial sweetener as “cause of death”, I MIGHT re-evaluate. Until then, researchers need to find something else to do with their time. This same article over and over again in every single magazine and newspaper is soooo boring and deceptive. About to drink a diet soda.

  6. Avatar David Eccles says:

    This article is bogus, a ploy to gain publicity and provides no useful information. Does the author get paid for this? The study shows no cause and effect. There are many reasons why the correlation is not necessarily valid. Any reader could name them. One, diet soda drinkers could be overweight already and are trying to cut down on calories. I have diabetes and have used artificial sweeteners and diet drinks to lose over 30 pounds. I do a lot of my own cooking and it’s working. I use sweeteners in moderation. I dilute my diet drinks with 1/2 water since I like it better than just water which can dry out my mouth.

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