You Can Have Your Diet Coke and Enjoy It Too
A decade-long debate about artificial sweeteners just got some clarity. A 2025 meta-analysis published in Frontiers in Nutrition analyzed nine randomized controlled trials involving 1,457 participants and found no significant differences in metabolic outcomes between people who drank artificially sweetened beverages and those who drank unsweetened beverages like water or tea.
No difference in weight. No difference in waist circumference. No difference in blood glucose, insulin resistance, cholesterol, triglycerides, or blood pressure.
If you've been told that diet soda causes weight gain, disrupts your metabolism, or increases your disease risk—the evidence doesn't support it.
What the Research Actually Measured
Researchers at the First Hospital of Hunan University of Chinese Medicine conducted a systematic review and meta-analysis, searching PubMed, Embase, Web of Science, and Cochrane Library databases through March 2025. They included only randomized controlled trials that compared artificially sweetened beverages (ASBs) to unsweetened beverages (USBs) with follow-up periods of at least six months.
The nine studies included participants who were healthy, overweight or obese, or had type 2 diabetes. Follow-up ranged from 24 to 77 weeks—long enough to detect meaningful metabolic changes if they existed.
The researchers extracted data on every major metabolic marker:
Body weight and waist circumference
Fasting plasma glucose and glycated hemoglobin (HbA1c)
Homeostatic model assessment for insulin resistance (HOMA-IR)
Total cholesterol, triglycerides, HDL cholesterol, and LDL cholesterol
Systolic and diastolic blood pressure
Energy intake
Then they analyzed the data using both fixed-effect and random-effects models, accounting for heterogeneity across studies.
The Results Were Consistent
Across all nine studies and 1,457 participants, artificially sweetened beverages showed no statistically significant effects on any metabolic outcome when compared to unsweetened beverages.
Body weight? No significant difference (SMD, -0.10; 95% CI, -0.37 to 0.18; p=0.50).
Waist circumference? No significant difference (SMD, -0.10; 95% CI, -1.67 to 1.47; p=0.90).
Fasting blood glucose? No significant difference (SMD, -0.03; 95% CI, -0.43 to 0.37; p=0.88).
HbA1c? No significant difference (SMD, 0.60; 95% CI, -0.02 to 1.21; p=0.06).
Insulin resistance (HOMA-IR)? No significant difference (SMD, 0.03; 95% CI, -0.68 to 0.74; p=0.93).
Total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol? All showed no significant differences between groups.
Blood pressure? Both systolic (SMD, -0.35; 95% CI, -1.60 to 0.90; p=0.58) and diastolic (SMD, 0.25; 95% CI, -0.25 to 0.76; p=0.33) showed no significant differences.
Even energy intake—the theory that artificial sweeteners make you hungrier—showed no significant difference (SMD, 0.53; 95% CI, -0.39 to 1.46; p=0.26).
What This Means in Practice
This analysis tells us that switching from sugar-sweetened beverages to artificially sweetened beverages doesn't pose metabolic risks over six months or longer. And switching from artificially sweetened beverages to unsweetened beverages doesn't provide metabolic benefits.
The choice between a diet soda and water is metabolically neutral.
That doesn't mean artificial sweeteners are a health food. It means they don't cause the metabolic dysfunction that many nutrition influencers claim. The fear-mongering around diet soda isn't supported by controlled research.
If you enjoy diet soda and it helps you avoid sugar-sweetened beverages, the metabolic evidence supports that choice. If you prefer water or tea, that works too. Your decision should be based on preference and sustainability, not unfounded concerns about weight gain or disease risk.
The Important Limitation You Should Know
This meta-analysis combined different artificial sweetener formulas—aspartame, sucralose, stevia, and others—into one category of "artificially sweetened beverages." That means it can't tell us whether specific sweeteners have different effects.
Individual compounds may behave differently in the body. Research on specific sweeteners at specific doses is ongoing, and some preliminary evidence suggests personalized responses based on gut microbiome composition. But lumping all artificial sweeteners together and claiming they're all dangerous isn't supported by the controlled trial data we have.
The researchers acknowledged this limitation explicitly: "Given this study applied a heterogeneous ASB formula, it could not adequately consider the role of specific artificial sweeteners."
Context: This Isn't About Sugar-Sweetened Beverages
An important clarification: This study compared artificially sweetened beverages to unsweetened beverages, not to sugar-sweetened drinks.
We already have extensive evidence that sugar-sweetened beverages contribute to weight gain, type 2 diabetes, and cardiovascular disease. Regular soda, sweetened tea, energy drinks, and fruit juices with added sugar are major sources of excess dietary sugar and calories.
The question this research addressed was whether replacing sugar-sweetened beverages with artificially sweetened options poses additional metabolic risks. The answer is no.
If you're choosing between regular Coke and Diet Coke, the metabolic evidence clearly favors Diet Coke. If you're choosing between Diet Coke and water, the metabolic outcomes are equivalent.
Why the Fearmongering Persists
Despite consistent evidence from randomized controlled trials, artificial sweeteners remain one of the most controversial topics in nutrition. Why?
Part of it is observational study confusion. Some large cohort studies have found associations between diet soda consumption and weight gain or metabolic disease. But these studies can't establish causation—people who drink diet soda may already have weight concerns or metabolic conditions, which is why they're choosing diet versions.
Randomized controlled trials, where researchers assign people to drink either artificially sweetened or unsweetened beverages, control for these confounding variables. And those trials consistently show no metabolic harm.
Another factor is the appeal of "natural" eating. Artificial sweeteners sound... artificial. And in a wellness culture that glorifies "clean" eating and demonizes processed foods, artificial sweeteners are an easy target.
But "natural" doesn't always mean better. Arsenic is natural. So is botulinum toxin. The dose and context matter more than the origin.
The Bottom Line
A comprehensive meta-analysis of nine randomized controlled trials found no metabolic differences between artificially sweetened beverages and unsweetened beverages across any marker measured—weight, waist circumference, glucose metabolism, lipid profiles, blood pressure, or energy intake.
This doesn't mean you should drink diet soda. It means you don't need to fear it if it helps you avoid sugar-sweetened alternatives or if you simply enjoy it.
Your beverage choices should be based on preference, sustainability, and overall dietary context—not on unfounded claims about metabolic damage.
If you want the Diet Coke, have the Diet Coke.
Source: Qin, L., Yu, Y., & Yu, R. (2025). Artificially sweetened beverages do not influence metabolic risk factors: a systematic review and meta-analysis. Frontiers in Nutrition, 12, 1482719. https://doi.org/10.3389/fnut.2025.1482719
