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In my last post, Diet Soda and the Brain, I described how artificial sweeteners like sucralose may affect hunger, memory, and gut-brain signaling. That raised an obvious question: If diet soda isn’t the safe choice we thought, what about regular soda?
The evidence against sugar-sweetened beverages is even more consistent, and has been for years. The more interesting story is why so many of us remain unsure of that. Some of that uncertainty didn’t happen by accident. It was manufactured.
What the Independent Science Shows
Sugar-sweetened beverages are the largest source of added sugar in the American diet. A systematic review conducted for the 2025–2030 Dietary Guidelines for Americans concluded that these drinks may raise the risk of type 2 diabetes in adults, based on studies published between 2000 and 2024. A separate 2025 review found the pattern wasn’t subtle: The more sugar-sweetened beverages people drank, the higher their diabetes risk climbed.
This makes biological sense. Sugary drinks deliver a large, fast dose of fructose and glucose with none of the fiber or protein that would normally slow absorption. Over time, that pattern causes weight gain, insulin resistance, and elevated triglycerides — the same factors that lead to type 2 diabetes.
A Pattern Too Consistent to Be Coincidence
In 2016, Dr. Dean Schillinger of UCSF led a review of 60 studies published between 2001 and 2016 on sugary drinks, obesity, and type 2 diabetes. The pattern was undeniable: 34 studies found a link, and only one of those was industry-funded. All 26 studies finding no link were funded by the beverage industry. “This industry seems to be manipulating contemporary scientific processes to create controversy and advance their business interests at the expense of the public’s health,” the authors concluded.
That wasn’t an isolated finding. A separate analysis in PLOS Medicine found industry-funded beverage studies were roughly five times more likely to find no link between sugary drinks and weight gain than independently funded ones. A skew this consistent, across years and research teams, stops looking like coincidence.
The Playbook
It isn’t just which studies get funded, it’s which messages get amplified. In 2015, internal documents revealed Coca-Cola had funded and helped shape the Global Energy Balance Network, a group whose public message emphasized exercise over diet, deflecting attention from sugar’s role in weight gain. Coca-Cola reportedly helped choose its leadership and messaging while internally calling it a “weapon” in a “war” with public health advocates. The network dissolved once this came to light.
A Boston University study found that between 2011 and 2015, Coca-Cola and PepsiCo funded 96 national health organizations while at the same time lobbying against at least 28 public health bills aimed at reducing consumption of soda. As Schillinger put it: “We are in a public health war with diabetes right now. In every war there is propaganda… we are being played.” The American Beverage Association states that its scientific research mission is to “inform and clarify discussion through scientific inquiry held to the highest standards of integrity.” Although industry funding doesn’t automatically invalidate a study, it does raise suspicion when a study’s conclusions correlate so reliably with those of the industry that paid for it.
The Mental Health Connection
There’s another piece of this story that doesn’t get talked about enough: diabetes, obesity, and mental health are closely linked, and each one can make the others worse. Research shows that people with depression are more likely to develop type 2 diabetes, and people with type 2 diabetes are more likely to become depressed. Scientists think this happens because diabetes, obesity, and mental illness all involve some of the same problems inside the body, including ongoing inflammation and stress hormones that stay elevated for too long. The connection is even stronger in people with serious mental illnesses like schizophrenia, who develop type 2 diabetes two to five times more often than the general population, partly because some medications used to treat these illnesses cause weight gain and directly affect blood sugar. Sugary drinks exacerbate the problem. By raising the risk of obesity and diabetes, they may also be raising the risk of mental illness.
Putting It Together
A bigger picture is emerging, one larger than any single sweetener. Diet soda may quietly reshape hunger signals and brain chemistry while regular soda drives obesity, diabetes, and possibly mental illness. The evidence for these links is supported by decades of research. And for just as long, the beverage industry has conducted a well-funded effort to keep the public in the dark.
This doesn’t mean every soda drinker will develop diabetes, or that every industry-funded study is worthless. But it does mean that when evaluating claims about sugar and health, it’s worth asking who funded the study and what they had to gain. In the meantime, the most reliable way to support your physical and mental health is to focus on water, whole foods, and occasional treats. You don’t have to be rigid about this, but you may find the effort is well worth the benefits.
