- Fructose, found in table sugar, syrups and sweet drinks, is handled mainly by the liver, which can turn extra fructose into fat.
- In the Framingham study, people drinking a sugary drink every day had 61% higher odds of fatty liver than non-drinkers.
- Whole fruit is different: its fiber and water slow absorption and it is linked with good health.
- WHO advises keeping free sugars below 10% of daily calories, and ideally below 5% (about 6 teaspoons).
Most people know sugar is bad for teeth and blood sugar. Fewer know that it matters for the liver too. Metabolic dysfunction-associated steatotic liver disease (MASLD) is driven by several things, including extra calories, insulin resistance and genes. Added sugar, and fructose in particular, is one of the dietary factors most closely linked with it. The good news is that cutting back on added sugar is one of the simplest, fastest changes you can make. For the bigger picture, see Fatty Liver (MASLD) Explained.
How the liver handles fructose
Table sugar (sucrose) is half glucose and half fructose. High-fructose corn syrup, honey, jaggery and fruit juice concentrates also contain plenty of fructose. Glucose can be used by almost every cell in the body. Fructose is different: most of it is taken up by the liver on its first pass from the gut.
What happens when the liver gets more fructose than it needs
Based on Jensen et al., J Hepatol 2018.
This process of making new fat from sugar is called de novo lipogenesis. In people with fatty liver it runs faster than usual. Fructose may also make the liver more resistant to insulin and encourage inflammation. In a 10-week study, adults with overweight who got a quarter of their calories from fructose-sweetened drinks showed more new fat-making in the liver and gained more deep belly fat than those given glucose-sweetened drinks with the same calories. Read more about deep belly fat in Visceral Fat and Metabolic Health.
What the studies show
Much of the human evidence comes from observational studies, which show links rather than proof of cause. But the findings point in the same direction, and short feeding trials help explain why.
Ma et al., J Hepatol 2015 (2,634 Framingham adults; adjusted for weight and diet); Schwarz et al., Gastroenterology 2017 (calories kept the same).
In the Framingham Heart Study, people who drank sugar-sweetened drinks daily were more likely to have fatty liver on CT scans than people who drank none, even after allowing for body weight, alcohol and the rest of their diet. Diet soda did not show the same link. In the children’s study, sugar intake was cut from about 28% to 10% of calories while total calories stayed the same. Liver fat and the rate of new fat-making both fell within just nine days.
Fruit is different
Whole fruit contains fructose, but in a very different package. An apple or a bowl of papaya brings fiber, water, vitamins and plant compounds. It takes time to chew, fills you up and releases its sugar slowly, so the liver is not flooded. Studies generally link whole fruit with lower, not higher, risk of type 2 diabetes and heart disease.
- Whole fruit: guava, apple, orange, papaya, berries
- 1–2 portions a day as part of meals or snacks
- Fruit with curd or a few nuts
- Packaged and even fresh fruit juice
- Smoothies with added sugar or honey
- Fruit-flavored drinks and dried fruit sweetened with sugar
Our guide to the best fruits for prediabetes has portion ideas that work for the liver too.
How much sugar is too much?
The World Health Organization recommends that adults and children keep free sugars below 10% of daily calories, and suggests that below 5% brings further benefit. Free sugars are sugars added to food and drinks by manufacturers, cooks or you, plus sugars naturally present in honey, syrups and fruit juices.
Free sugar limits on a 2,000-calorie day (1 teaspoon is about 4 g)
WHO Guideline: sugars intake for adults and children, 2015. Cola sugar content varies by brand and country; check the label.
Finding hidden sugars
Much of the sugar we eat is not spooned in. It hides in packaged foods, including ones that do not taste very sweet. Checking the label takes seconds once you know where to look. See How to Read Nutrition Labels for a full walkthrough.
- Look for “added sugars” on the nutrition panel where it is listed, and compare products per 100 g.
- Check the ingredients list: the higher sugar appears, the more there is.
- Spot other names: sucrose, glucose-fructose syrup, corn syrup, invert sugar, maltose, dextrose, jaggery, honey, fruit juice concentrate.
- Watch “healthy” foods: flavored yogurt, breakfast cereals, granola bars, malt “health drink” powders, ketchup and sauces.
- Remember home sources too: sugar in chai, sweets like jalebi and laddoo, and sweetened lassi.
Simple swaps
Replacing sugary drinks often cuts a lot of calories too. Try our Calorie Calculator to see how it fits your daily target.
MythHoney and jaggery are healthy sugars, so they do not count.
FactHoney, jaggery and coconut sugar are still free sugars rich in fructose. They count toward the same daily limit as white sugar.
Common questions
Is fructose worse than glucose for the liver?
In controlled studies, large amounts of fructose raise liver fat-making more than the same calories from glucose. In everyday life both come together in sugar, so the practical advice is simply to eat less added sugar.
Are diet drinks a good substitute?
Diet soda was not linked with fatty liver in the Framingham study. It can be a stepping stone away from sugary drinks, but water, plain tea and coffee are the best long-term choices.
Does sugar alone cause fatty liver?
No. Extra calories from any source, low activity, insulin resistance, genes and alcohol all play a part. Sugar is one factor you can change easily. See What Causes Fatty Liver?
- The liver turns excess fructose into fat through de novo lipogenesis.
- Daily sugary drinks are linked with higher odds of fatty liver; cutting sugar can lower liver fat within days.
- Whole fruit is fine; juices, syrups, honey and jaggery count as free sugars.
- Aim for under 10% of calories from free sugars, and ideally under 5% (about 6 teaspoons).
- Next: Exercise for Fatty Liver: How Much Helps.
Sources
- Jensen T, Abdelmalek MF, Sullivan S, et al. Fructose and sugar: a major mediator of non-alcoholic fatty liver disease. J Hepatol. 2018;68(5):1063–1075.
- Ma J, Fox CS, Jacques PF, et al. Sugar-sweetened beverage, diet soda, and fatty liver disease in the Framingham Heart Study cohorts. J Hepatol. 2015;63(2):462–469.
- Stanhope KL, Schwarz JM, Keim NL, et al. Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans. J Clin Invest. 2009;119(5):1322–1334.
- Schwarz JM, Noworolski SM, Erkin-Cakmak A, et al. Effects of dietary fructose restriction on liver fat, de novo lipogenesis, and insulin kinetics in children with obesity. Gastroenterology. 2017;153(3):743–752.
- World Health Organization. Guideline: sugars intake for adults and children. Geneva: WHO; 2015.
- European Association for the Study of the Liver, European Association for the Study of Diabetes, European Association for the Study of Obesity. EASL–EASD–EASO Clinical Practice Guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD). J Hepatol. 2024;81(3):492–542.
This article is for general education and is not a substitute for advice from your own doctor or healthcare team.