TL;DR: One 12-oz can of either diet or sugary soda daily raises your risk of fatty liver disease (NAFLD) by 50–60%. Swap it for water and cut the risk by 13–15%. Yes, really.
You’ve heard it before: “Switch to diet soda—it’s zero sugar, zero guilt.”
Turns out, your liver doesn’t care about the calorie count.
An extensive new study* (124,000 people in the UK BioBank study with 10-year follow-up) was just reported at a major European gut conference, and the results are not what we would have all expected:
- 1 can of regular soda/day → +50% NAFLD risk
- 1 can of diet soda/day → +60% NAFLD risk
Even worse? Switching from sugary to diet soda gave zero protective benefit. The only swap that worked: water.
Here is one report on the study. A link to the original conference report is hard to find.*
https://edition.cnn.com/2025/10/06/health/diet-sugary-soda-fatty-liver-cancer-wellness
Why Diet Soda Isn’t “Safe” for Your Liver
We’ve known for quite a while that sugary drinks are hard on the liver. Fructose is called “alcohol without the buzz” by one doctor who lectured far and wide on the dangers of high fructose cory syrup. It is very damaging to the liver. But diet soda? How is that bad for your liver? Well, the mechanisms are not straightforward:
- Gut microbiome chaos – Artificial sweeteners like sucralose and aspartame alter the kind of bacteria that thrive in the gut, increase inflammation, and change fat metabolism.
- Appetite sabotage – The sweet taste without calories may increase cravings, leading to overeating and weight gain. After all, 85% of the link between diet soda and NAFLD was mediated by BMI.
- Insulin confusion – They say some sweeteners may still trigger insulin release, which promotes fat storage. (I’m not so sure about this mechanism.)
This Isn’t Just One Study
The findings line up with:
- UK Biobank (2023): >2L/week of diet soda = 137% higher NAFLD odds
- NHANES (2023): Daily diet soda drinkers = 2x MASLD (metabolic-dysfunction associated steatotic liver disease)
Meanwhile, the Framingham Heart Study saw no link—but only in younger adults and at lower intakes—dose and age matter.
Your 2-Minute Action Plan
- Take inventory of what you actually drink. – Track sodas (diet and regular) for 3 days.
- Swap 1-for-1 with water – Add lemon, cucumber, or a splash of 100% juice if plain water feels boring.
- Check your liver labs – If ALT/AST are creeping up, this is your cue.
Bottom line: For liver health (and T2D control), all soda is suspect. Water wins. Again.
*Study presented at UEG Week 2025; full paper pending peer review.
