Are all calories the same? In a new study, obese children who reduced their sugar intake—while holding their overall calorie intake constant—showed significant improvement on a range of metabolic measures associated with diabetes risk.
The study speaks to a core question in nutritional research: Does sugar play a special role in causing diabetes and metabolic disorders, or is consuming too many calories alone the cause of health problems?
To find out, researchers from the University of California-San Francisco (UCSF), and Touro University California recruited 43 Hispanic and African American children between the ages 9 and 18 who were being treated at a UCSF obesity clinic. All had at least one symptom of metabolic syndrome, a cluster of conditions including elevated cholesterol, hypertension, and high blood sugar that increase one's risk of diabetes and other conditions.
On average, the participants received about 28% of their daily calories from sugar at the beginning of the study. Working with nutritionists, they modified their diets to reduce daily sugar intake to about 10%—while holding calories constant. For instance, baked potato chips and other high-carb foods replaced items like sugar-sweetened yogurt or soft drinks.
The study was funded by the National Institutes of Health and published in Obesity.
Participants followed the new regimen for nine days and then underwent a series of tests. On average:
- LDL cholesterol, which is associated with heart disease, dropped 10 points;
- Diastolic blood pressure declined by five points;
- Triglycerides, a type of fat that contributes to heart disease, dropped 33 points; and
- Fasting blood sugar and insulin levers fell significantly.
"This paper says we can turn a child's metabolic health around in 10 days without changing calories and without changing weight–just by taking the added sugars out of their diet," said study lead author Robert Lustig, a pediatric endocrinologist at the Benioff Children's Hospital of UCSF. Lustig has been a vocal advocate for exploring the special role sugar may play in harming health.
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For Lustig, the study provides vindication. "This is causation," he said. "We reversed virtually every aspect of their metabolic syndrome."
Some other experts agreed the study was well-designed and provided more evidence that sugar intake is linked to metabolic syndrome. "[The study] provides a proof of concept that in a high risk population, reducing consumption of added sugar can have multiple metabolic benefits," Frank Hu of the Harvard T.H. Chan School of Public Health told the New York Times' "Well" blog.
Mark Corkins, professor of pediatrics at University of Tennessee Health Science Center, also praised the study, but said he hoped its findings do not distract from broader issues related to obesity and diabetes prevention. "Too much calorie intake is still the biggest problem," he told TIME.
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Groups affiliated with food and beverage manufacturers were most critical of the study. "The broad conclusions and policy recommendations in this study only serve to further the author's policy agenda without a sufficient scientific foundation," said Leon Bruner, chief science officer at the Grocery Manufacturers Association.
William Dermody, VP of policy at the American Beverage Association, said the study was flawed and argued there was nothing "unique" about calories from sugar.
Amid the controversy, U.S. officials are already taking steps to potentially curb sugar consumption. In July, FDA recommended food labels include how much added sugar a product contains and recommended that sugar intake not exceed 200 calories daily (McKay/Esterl, Wall Street Journal, 10/27; O'Connor, "Well," New York Times, 10/27; Park, TIME, 10/27).
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