Does Drinking Diet Soda Cause Diabetes?

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Nora Saul, M.S, R.D., L.D.N., C.D.E.

Nora Saul is a Certified Diabetes Educator and Manager of Nutritional Education at Joslin Diabetes Center.

A reader wrote to say, “I just read a story in the news that said research published by the ADA shows diet soda can make you obese.  Should I stop drinking diet soda?”

I saw that report, too, and at first it’s hard to know what to think. But before you start to empty your fridge, here’s some background to that report.

Diatribes against diet soda have been all the rage for the last few years.  It has been linked with an increased risk of weight gain and of getting diabetes.

Now, drinking diet soda has been associated with increasing abdominal girth, (the type that often coincides with metabolic syndrome and type 2 diabetes).

The results of the San Antonio Longitudinal Study of Aging, which was presented at the June meeting of the American Diabetes Association, linked diet soda consumption with increasing waistlines. 

The study followed 474 participants aged 65 to 74 over an average of 9 years and looked at their change in waist circumference over time in comparison to their diet soda consumption.

Soda drinkers had a 70% greater increase in waist girth than abstainers. Those drinking the most diet sodas had the greatest gains in girth.  Those drinking 2 or more diet sodas a day had 5 times the increase in waist circumference as their non-imbibing peers.  The results were controlled for initial waist circumference, diabetes status, leisure-time physical activity level, neighborhood of residence, age and smoking status at each measurement period, as well as sex, ethnicity and years of education.

The study expands the findings of a previous study by the same authors in 2008 where consuming more than 21 diet sodas  a week was associated with almost double the risk of becoming overweight.

Does this prove you should raid your refrigerator and throw out all the cans and bottles of diet soda you have stocked?  That every can of soda is another pound on the scale?

Not necessarily.

Let’s begin with some basics about these studies.  They are epidemiological or observational studies.  No intervention happens during the study period; people meeting certain criteria are simply watched over a period of time to see what happens.

The gold standard for research is the double-blind, controlled intervention study.  An example using soda would be that  200 people with diabetes of the same age, sex, weight and diabetes control would be divided into two even groups.  One group would be asked to drink two cans of diet soda a day, and the other group would drink water disguised to look  and taste like diet soda.  The two groups would be given the same food in a quantity calculated to meet their caloric needs.   At the end of a specified time period, both groups would be weighed to see if there was any change. Neither the researchers nor the participants would know which group drank the real diet soda.  It is hard and costly to do this type of study, so a lot of research is done observationally first.

In the San Antonio study, many things could account for the results.

  • It could be that all the people who drink diet soda have something else in common that is the real cause of their weight gain and increased abdominal girth.
  • It could be that people who drink diet sodas feel they are reducing their calorie consumption in this area, so they can eat more of other things they like .
  • It could also be that the sweet taste of the sodas devoid of calories stimulates the appetite in some way, causing people who drink diet sodas to eat more.

Right now we just don’t know.

Nobody is recommending diet soda as a nutritional powerhouse.  Essentially it is a soup of chemicals with not much to recommend it nutritionally.  The reason it is suggested for people with diabetes is because the more healthful alternatives–water, water with a splash of juice, milk, even coffee and tea–don’t always appeal to people.

If you decide to drink diet soda, do so in moderation and be careful of calories coming from other sources.  And, if it’s a choice between regular soda and diet soda for people with diabetes, the diet soda still wins, at least until we have some conclusive proof that it is dangerous.


For more information on diabetes:

17 Responses to Does Drinking Diet Soda Cause Diabetes?

  1. I drink a lot of coca cola. not diet coca cola.
    coca cola give me diabetes.

  2. joslin reply says:

    Dear Obat Diabetes:
    Neither regular or diet soda is a direct cause of diabetes. However, the calories in regular soda can lead to weight gain. Because regular soda contains a large amount of carbohydrate in a small liquid volume it tends to quickly spike blood sugar and is therefore not recommended as part of a healthy diet.

  3. Joseph says:

    I agree, there are many possible explanations for the outcome of the study. One that stands out to me is the misunderstanding surrounding food consumption and healthy diet and exercise.

    Diet soda is a popular alternative to sugar flavored beverages but often times people will compensate by consuming high calorie foods in larger quantities e.g. more fast food, sugary desserts, etc. It’s in the same vein as the person who burns 200 calories in the gym then rewards himself with a 400 calorie pastry – the misplaced belief that the healthy activity will be enough to help them lose weight. For most people, weight loss is a combination of good nutrition and exercise; sometimes we indulge our desire for high calorie foods and as long as this happens only on rare occasions it shouldn’t cause significant weight gain.

    Each person is different, some will gain weight even while drinking diet soda, others will not; a blanket call for tossing out diet soft drinks would be taking it a bit too far.

  4. Who drinks diet soda? People who are either overweight or have a weight problem. ” “70% greater increase in girth increase” is biased reporting. If the controls increased by 1/10 if an inch, and diet soda by 1.7/10 of an inch, then that’s 70 %. You have to see the real data.

  5. LORAY says:


  6. Joseph Hanak says:

    I am so glad to see this e-mail. For some time an idea bugs me and wanting to write to someone about it. What I think (maybe naively) that if we cosume sweat something, the brain gets the message and instructs the pencrias to produce more insulin. but if the sweatness iis not from carbohydrates the insuline is useless unless some carbohydrate in some form is also consumed before the insuline loses its activity. If sweatness message repeatedly produced by artificial sweatener the pancreas may disregard the brain”s order, which dosn’t know the source of sweatness. So, in some cases this confusion may lead to diabetes?

  7. Fausto Fernandez, MD says:

    NOBODY has sugar in his/her blood. What you have is GLUCOSE. Sugar (sucrose) is half fructose and half glucose. Fructose does not need insulin to enter the cell or the intermediary metabolism. There was a very good Swdish study about 30 years ago that showed that people who consumed good amounts of sucrose reduced the risk of diabetes. Sucrose is the best appetite suppresant there is.
    I am a diabetic myself, and take four teaspoons of sugar in my coffee, and I have 4-5 cups a day; I am in excellent control, HbA1c of 6.5, and I am only on metformin 1000 mg BID. This am my SMBG was 105. There’s no reaon to avoid sugar, and probably sugar is GOOD for you, since it provides you with fructose (which does not stimulate insulin secretion) and kills your appetite. By the way, the great majority of my diabetic patients who follow my diet have HbA1c’s of between 6.0 and 6.9.

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  13. Diet soda cannot be a cause of diabetes
    What are diabetes

  14. David says:

    Diet soda doesn’t contain sugar, but it contains artificial sweeteners. Because of this, people probably won’t get diabetes from it. However, there has been many research studies that indicate many dangers with artificial sweeteners. They’re linked to cancer and many health problems. The best thing to do is probably drink regular soda when you want to and drink it in moderation.

  15. St. John says:

    I drink 3 or more cans of Diet Coke. I’m almost 50, and my girth is the same. I, however, walk about an hour and half a day.

  16. St. John says:

    LORAY, get your facts when pointing fingers about “artificial sugar.” “Aspartame” is an artificial sweetener. “Aspartame” doesn’t cause cancer, at least scientists haven’t concluded that. Scientists have tested aspartame for a long time now.

    If people are worried about getting obese, don’t over eat, walk, exercise, instead of sitting around.

  17. rose says:

    I am SURE diet soda increased my girth. I cut back on my eating and to not drink high calorie juices/drinks and since I never really liked drinking plain water – I went all out to diet soda.

    Its like all the air in the sodas blew up my stomach – I began lookin like I was pregnant – now I hope once I get rid of ALL sodas it will come back to NORMAL.

    BEWARE – it is TRUE – diet soda is a FARCE – it increases the appetite and it increases the girth. The trade off of less calories is not there, caus it makes u crave sweets.

    So NOWAY to DIET SODAS !!!

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