Cutting Sugar Made Obese Kids Healthier in 10 Days

A little girl holds a handful of candy
(Image credit: Liudmila P. Sundikova/

There can be no more dancing around the fact that, for children, consuming added sugar contributes to a litany of chronic diseases, particularly obesity, Type 2 diabetes and heart disease, scientists concluded in new research published today (Oct. 27).

In the study, researchers closely monitored 43 obese children and found that reducing the consumption of added sugar — even while maintaining the same number of calories, and the same amount of non-sugary junk food such as potato chips — led to a dramatic improvement in a cluster of health measures in just 10 days.

The kids lowered their cholesterol, blood pressure and blood sugar and lost a little weight, too, despite no change in their calorie intake or physical activity.

"The positive message is that you can very quickly reverse a bad picture [of health] in a very simple way," by removing added sugars, said Jean-Marc Schwarz, a professor at Touro University California near San Francisco and senior author of the paper. "I have never seen results as striking or significant."

The study bolsters the evidence that added sugar is a harmful ingredient that needs to be regulated more strictly, said lead author Dr. Robert Lustig, a pediatric endocrinologist at the Benioff Children's Hospital of the University of California, San Francisco.

Added sugar refers to natural sweeteners that are added to food to improve taste, extend shelf life or lower costs. The sweeteners are usually derived from sugar cane or beets, corn, sorghum, honey, maple syrup or agave. They are added to foods as varied as soups and salad dressing. [Added Sugar in Some Popular Foods and Drinks (Infographic)]

Added sugar does not include sugars found naturally in food, such as the fructose or fruit sugar found naturally in blueberries.

A study published in 2012 found that of the approximately 600,000 items in the U.S. food supply, 74 percent have added sugar. Americans consume 385 calories or 23 teaspoons of added sugar daily, on average, according to the American Heart Association. That's nearly 40 pounds of added sugar per person annually.

Half of this sugar is in beverages such as sodas, energy drinks, fruit drinks and teas, according to data from the Centers for Disease Control and Prevention. Nearly 20 percent comes from non-dessert foods eaten for breakfast, lunch or dinner. The rest of the added sugar is in snacks and desserts.

In the new study, Schwarz and Lustig enrolled 43 African-American and Latino children who were obese and had at least one other chronic metabolic disorder, such as high blood pressure or cholesterol. The researchers' goal was to isolate the effect of added sugars on the children's metabolism, keeping all other dietary inputs equal.

So, the researchers constructed a diet in which added sugar was replaced by another kind of carbohydrate. They removed or reduced foods such as pastries and breakfast cereals and replaced them with bagels, for example. The overall levels of fat, protein, carbohydrates and calories in their typical daily diet did not change; the kids still could eat chips and fatty foods. But the researchers reduced the kids' consumption of added sugar from 28 percent to 10 percent of their total daily calories, in accordance with the World Health Organization's recommendation.

Virtually every health measure improved significantly for these children within 10 days of switching to this diet, even though the kids continued to eat some junk food, Lustig said. Improvements included lower blood pressure, lower levels of fats and sugars in the blood stream, and improved liver and pancreas function.

Most of the children reported being too full on the new diet, despite the equal calories; 42 of the 43 found the diet very palatable.

The study comes amid proposed changes in food labeling in which the Food and Drug Administration would require food manufacturers to state the amount of added sugars in their products and also a "daily percent value" for added sugars, in concordance with the WHO recommendation of 10 percent total.

The food industry has opposed such changes, citing a lack of scientific evidence for the ill effects of added sugar. Yet these latest results, when combined with other recent studies, demonstrate not merely an association but a cause-and-effect relationship — it shows that added sugar leads to metabolic syndrome, Lustig argued. [Why Is Too Much Sugar Bad for You?]

"This study demonstrates that 'a calorie is not a calorie,'" Lustig said. "Where those calories come from determines where in the body they go. Sugar calories are the worst, because they turn to fat in the liver, driving insulin resistance, and driving risk for diabetes, heart, and liver disease. This has enormous implications for the food industry, chronic disease, and health care costs."

The dramatic results have left some impressed but nevertheless skeptical.

"While this work is suggestive of a dramatic beneficial health effect, there are too many careful, well-controlled studies on this topic that do not find such unique, dramatic results," said Barry Popkin, a professor of nutrition University of North Carolina at Chapel Hill School of Public Health, who has advocated for a tax on added sugar in drinks.

"That the results [of this new study] are so different [from previous studies] means that scientists across the globe must see if they can replicate these findings. To date, no one has found such dramatic results nor results that come close to replicating these, so I urge great caution in interpretation of these results."

The researchers said they hope to expand the study to determine whether the positive associations seen by eliminating sugars has a lasting effect on health.

Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on Live Science.

Christopher Wanjek
Live Science Contributor

Christopher Wanjek is a Live Science contributor and a health and science writer. He is the author of three science books: Spacefarers (2020), Food at Work (2005) and Bad Medicine (2003). His "Food at Work" book and project, concerning workers' health, safety and productivity, was commissioned by the U.N.'s International Labor Organization. For Live Science, Christopher covers public health, nutrition and biology, and he has written extensively for The Washington Post and Sky & Telescope among others, as well as for the NASA Goddard Space Flight Center, where he was a senior writer. Christopher holds a Master of Health degree from Harvard School of Public Health and a degree in journalism from Temple University.