This piece breaks down a new review from the University of Colorado that points to fructose as a specific driver of metabolic disease, explains how fructose differs from glucose in the body, and shares expert commentary on why certain sweeteners and whole foods matter for metabolic health.
“Drinking your calories” has long been a warning for anyone trying to manage weight, and the new review makes that warning sharper by singling out fructose. Sugary sodas, flavored coffees and many processed drinks often pack fructose-containing sweeteners that behave differently inside our bodies. The practical upshot is that not all calories act the same metabolically.
The authors analyzed evidence around common sweeteners like table sugar and high-fructose corn syrup, both of which are blends of glucose and fructose. That mix means you get two sugars with distinct effects on tissues and hormones. The review, published in Nature Metabolism, digs into how those differences play out at a biochemical level.
Glucose pushes insulin, which helps cells take up and store energy and can promote weight gain when calories are excess. Fructose, by contrast, has “unique metabolic effects that promote triglyceride synthesis and fat accumulation,” the researchers note. Those triglycerides are the main form of stored fat that accumulate when the body diverts incoming fuel into fat-building pathways.
“Under modern conditions of overnutrition, chronic excess fructose drives features of metabolic syndrome,” the authors wrote. (In this context, “overnutrition” means the body is consistently getting more calories and nutrients than it needs.) That chain — more triglyceride production, more stored fat — maps directly onto higher risk for insulin resistance and heart disease risk factors.
Lead author Richard Johnson, MD, put it bluntly in a university release: “fructose is not just another calorie.” He and his colleagues argue fructose operates as a metabolic signal that steers the liver and other tissues toward fat production and storage in ways that differ sharply from glucose. That signaling is why the review frames fructose as more than a simple energy source.
The report points out that fructose can bypass some of the regulatory stops glucose hits during metabolism, which can lower cellular energy and lead to buildup of compounds linked to dysfunction. Over time those shifts may contribute to a cluster of problems often labeled metabolic syndrome: obesity, insulin resistance and elevated cardiovascular risk. As the authors acknowledge, a review interprets existing work rather than proving a new experimental result, so it outlines risk and mechanism more than it delivers definitive causation.
Certified holistic nutritionist Robin DeCicco explained how fructose taxes the liver in a way glucose does not. “Unlike glucose, fructose metabolism … [can] make the liver turn the sugar into fat more easily, which is why the study said that it can lead to triglyceride regeneration,” said the New York City-based expert, noting that triglycerides are fat deposits in the arteries. She also warned about the insulin system: “Your pancreas doesn’t know how to keep up with the signaling of insulin, so it has to produce more and more insulin, and that’s what turns into diabetes,” she said.
Not all sources of fructose are equal in context. Whole fruits and vegetables contain fiber, water and micronutrients that blunt blood sugar spikes and promote fullness, so the metabolic impact differs from that of free fructose in processed foods and sweetened drinks. Some natural sweeteners such as stevia and monk fruit contain no fructose and may be better choices for people watching blood sugar or liver health, while options like maple syrup, honey, rice malt and glucose syrup vary in fructose content. “I’m not saying someone should go out of their way to use those, but if they already have a bad liver, if they’re overweight, if they’re diabetic … and if they need to bake or have something sweet, I would use one of those alternatives,” she said.
