Why Diet Soft Drinks Actually Make You Fat

For years, nutritionists and public health experts have focused on the health hazards of sugar and high-fructose corn syrup for their roles raising the risk of type 2 diabetes, obesity, and heart disease. Under the circumstances, it’s no surprise then that millions of people have turned to artificially sweetened diet soft drinks.

The implied promise, of course, has been that diet soft drinks should help people lose or maintain their weight. After all, zero calories should mean zero calories, right?

Well, it turns out that’s not the case. New research shows that the artificial sweeteners are not inert, and diet soft drinks are no better than those loaded with sugars. So I’ll give you my advice upfront: avoid all soft drinks like the plague.

And now I’ll explain why.


The Shocking Truth

Several long-term studies have found that people who consume diet soft drinks are more likely to become obese compared with those who don’t. The latest study along these lines focused on 474 seniors of either European-American or Mexican-American heritage who were tracked for nine or so years. People who regularly consumed diet soft drinks had, on average, waistlines that were almost three times bigger than those who never consumed diet soft drinks. Even those who only occasionally consumed diet soft drinks had big waistlines.[i]

It makes you wonder if the term “diet soft drinks” is false advertising.

There are several reasons why diet soft drinks can make you fat. And you’ll be surprised by them.

The first reason is that diet soft drinks give some people a license to eat more. That is, they believe that avoiding liquid calories gives them permission to indulge in other types of calories. For example, have you ever had a diet soft drink with a pizza? Diet soft drink or not, odds are that you ate way too many calories.

The second explanation comes from neuroscientists. Their research has found that sweet foods activate the “reward” centers of the brain. That’s because our taste buds and brain really like sweet foods. In fact, neuroscientists have determined sweet-tasting foods and drinks create a drug-like “high” related to an increase in dopamine, a brain chemical involved in pleasurable feelings. Not surprisingly then, an addiction to sweet-tasting drinks and foods can involve cravings and withdrawal symptoms that are eerily similar to what happens to drug users.[ii] [iii] [iv] [v] Skeptical? Just think about how some people crave chocolate.

And yet, the scientific evidence indicates that artificial sweeteners do not activate the reward centers of the brain. Instead of dampening our cravings for sweets, they have the opposite effect. We end up gobbling more to satisfy the brain and our cravings.[vi]

Prediabetic Changes

The third reason has more to do with the body than the brain. Consuming something sweet, whether it’s sugar or artificial, triggers the body’s secretion of insulin. Sometimes even the smell of something sweet, such as cinnamon rolls, prompts the release of insulin.

Normally, our bodies secrete insulin after we eat food. One of insulin’s jobs is to lower blood sugar, because very high blood sugar levels are dangerous. What happens when a person consumes something sweet but provides no calories? The insulin lowers blood sugar, which in turn triggers hunger. When that happens, people naturally want to eat, and they often eat more than they otherwise would.

Insulin’s other job is as the body’s fat-storage hormone. So when a person consumes a diet soft drink, the insulin gets ready to convert whatever food that follows to fat. In fact, high levels of insulin trigger a biological switch that turns off the production of muscle and increases fat, particularly around the belly, which happens to be the most dangerous type of fat (linked to diabetes and heart disease).[vii] Insulin also blocks the breakdown of fat cells, making it more difficult to lose weight.

Changes in Gut Bacteria

I’ve saved the best for last, because the very latest research is an absolute mind-blower. Artificial sweeteners change the bacteria in your gut, and these changes lead to prediabetes. It’s fair to assume that the shift in our gut bacteria also boost a person’s odds of gaining weight.

The researchers, who are based in Israel, tested the effects of artificial sweeteners (including saccharin, sucralose, and aspartame) on both laboratory mice and people. After consuming artificial sweeteners in water for 11 weeks, the animals developed glucose intolerance, a type of prediabetes. Because saccharin has the greatest effects, the researchers then conducted a second experiment in which they gave “safe” amounts of the sweetener to another group of mice.

The saccharin led to changes in more than 40 different types of gut bacteria, including a reduction in Lactobacillus reuteri, which happens to be one of the most important of our gut bacteria. When they transferred a small amount of these unbalanced bacteria to healthy mice, they also developed prediabetes. That proved the changes in bacteria caused prediabetes.

Then the researchers analyzed data from 381 nondiabetic men and women. People who consumed artificial sweeteners had more signs of prediabetes, including more abdominal fat, higher fasting blood sugar levels, and higher HbA1c levels.

Finally, they conducted an experiment with five men and two women who did not usually consume drinks or foods with artificial sweeteners. For six days, the subjects consumed an amount of saccharin considered safe by the U.S. Food and Drug Administration. Incredibly four of the seven subjects started to show prediabetic changes during this short period of time. Imagine how years of drinking diet soft drinks would have affected them!

The bottom line? It looks like artificial sweeteners contribute to the obesity epidemic they were meant to fight.

Still More Soft Drink Problems

There are still other serious problems with soft drinks. Colas contain phosphoric acid, a chemical that sharpens a soft drink’s flavor. The problem is that phosphorus-containing compounds reduce calcium absorption, which in turn will weaken bones.

Soft drinks also displace mineral-rich foods, and the high-phosphorus American diet specifically reduces calcium absorption, which affect bone development and strength.[viii][ix] [x] [xi] The problem is compounded by acid-blocking drugs, which are taken by millions of people. By decreasing stomach acid, these drugs boost the risk of osteoporosis.[xii]

But here’s another unexpected consequence of either sugary or diet soft drinks—they can cause fatigue. It turns out that large amounts of glucose or fructose (found in sugary drinks) or caffeine (found in colas and some noncola drinks) deplete potassium. The loss of potassium leads to muscle weakness, fatigue, and in some cases paralysis.

Low potassium and the consequential fatigue become most noticeable in people who consume large amounts of soft drinks, particularly colas. In case histories described in the International Journal of Clinical Practice, doctors reported that muscle weakness and fatigue were reversed after the patients stopped consuming soft drinks.[xiii] [xiv]

Soft Drink Alternatives

So, you might be thinking what could safely satisfy your desire for a sweet-tasting beverage. Ideally, I’d like to see you retrain your sweet tooth to not want soft drinks. It is possible, and I’ve seen countless patients swear off all soft drinks.

Our bodies were designed to consume water. Boring, you might be thinking! But it doesn’t have to be. There’s filtered water, bottled water, and bottled sparkling water. A squeeze of citrus, such as lemon, lime, or orange, can add a touch of flavor. Alternatively, Hint sells a line of fruit-infused waters, with such flavors as watermelon, pomegranate, grapefruit, and cherry. The added fruit provides literally just a hint of flavor with no extra calories. You’ll find more info at www.drinkhint.com.


[i] Fowler SP. Journal of the American Geriatrics Association, 2015: doi 10.1111/jgs.13376.

[ii] http://hereandnow.wbur.org/2015/01/07/sugar-health-research

[iii] http://mic.com/articles/88015/what-happens-to-your-brain-on-sugar-explained-by-science

[iv] http://www.conncoll.edu/news/news-archive/2013/student-faculty-research-suggests-oreos-can-be-compared-to-drugs-of-abuse-in-lab-rats.html#.VZF8UyjSxnE

[v] Blum K, Thanos PK, Gold MS. Dopamine and glucose, obesity, and reward

deficiency syndrome. Front Psychol, 2014;5:919. doi:


[vi] Yang Q. Gain weight by “going diet?” Artificial sweeteners and the neurobiology of sugar cravings. Yale Journal of Biology and Medicine, 2010;83:101-108.


[viii] Calvo MS, Tucker KL. Is phosphorus intake that exceeds dietary requirements a risk factor in bone health? Ann N Y Acad Sci, 2013;1301:29-35.

[ix] Tucker KL, Morita K, Qiao N, et al. Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The Framingham Osteoporosis Study. Am J Clin Nutr, 2006 Oct;84(4):936-942.

[x] Whiting SJ, Healey A, Psiuk S, et al. Relationship between carbonated and other low nutrient dense beverages and bone mineral content of adolescents. Nutrition Research, 2001;21:1107-1115.

[xi] Takeda E, Yamamoto H, Taketani Y. Increasing dietary phosphorus intake from food additives: potential for negative impact on bone health. Advances in Nutrition, 2014;5:92-97.

[xii] Schinke T, Schilling AF, Baranowsky A, et al. Impaired gastric acidification negatively affects calcium homeostasis and bone mass. Nature Medicine, 2009;15:674-681.

[xiii] Tsimihodimos V, Kakaidi V, Eilisaf M. Cola-induced hypokalaemia: pathophysiological mechanisms and clinical implications. International Journal of Clinical Practice, 2009; 63:900-902

[xiv] Packer CD. Cola-induced hypokalaemia: a super-sized problem. International Journal of Clinical Practice, 2009; 63:833-835.