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Pediatric endocrinologist Robert Lustig explains how our body reacts to fructose and why it’s so important not to get addicted to sugar (especially for children), based on the results of a study he co-authored.
Robert Lustig, specialist in neuroendocrinology and childhood obesity, professor at the University of California at San Francisco (USA), author of the book “Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity, and Disease, Hudson Street Press, 2013).
How did the idea for the study come about?
“It is known that excessive consumption of sugar is associated with the development of a number of diseases, united under the name “metabolic syndrome”, namely cardiovascular disease, type 2 diabetes, hypertension and problems with fat metabolism. We have separated the metabolic effect of sugar from its calorie and weight gain effects.”
Who participated?
“43 children aged 8 to 19, 27 of them were Hispanics and 16 African Americans. All were obese and had at least one comorbidity. They all consumed sugar in soft drinks, juices, baked goods, condiments.”
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How did we work?
“We aimed to reduce sugar intake in those who are already sick and see if their condition improves. But in the case of weight loss, it could be argued that the reason for the improvement is either a reduction in calories or weight loss. Therefore, the study was “low-calorie”: we compensated for the amount of calories from starch, and the subjects did not lose weight.
We asked study participants two questionnaires to understand how many calories their regular diet contains, how much fat, protein and carbohydrates they consume. For 9 days we were responsible for their food. The percentage of each of the main nutrients remained the same compared to homemade meals, but sugar was replaced with starch. For example, participants received bagels instead of cookies, baked potatoes instead of yogurt. We reduced the amount of sugar in their diet by 28%, down to one-tenth of the calories in their diet. We gave them extra snacks between meals, gave them a scale to take home, and they weighed themselves every day. If their weight was decreasing, we recommended eating more. On the last day, they returned to the hospital to check the results.”
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What are the results?
“We looked at three types of data. Diastolic blood pressure decreased by 5 points. Blood levels of substances associated with metabolic disease, liver function and metabolism have improved significantly. Glucose level decreased by 5 points. Glucose tolerance improved markedly. Fasting insulin levels dropped by half. In other words, the children’s metabolism improved in just 10 days, even when eating processed foods, by eliminating added sugar and replacing it with starch.
Children lost an average of 1 kg of weight, although the number of calories consumed did not decrease. Since the blood pressure dropped, we believe, though we cannot prove it, that the weight was reduced by the water. But in any case – whether it was water or muscle mass – the loss does not positively affect the metabolic status, but the study participants got better.
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What does this mean?
“First of all, the study provides conclusive evidence that not all calories are the same. Second, it became clear that obese children could improve in 10 days by eliminating added sugar from their diet. Third, we see that added sugar contributes to the development of metabolic syndrome in children. The study does not prove that sugar is the sole or even the main cause of metabolic syndrome, but it is clear that it is a highly modifiable cause. When it comes to chronic disease, the quality of our diet is probably even more important than the amount of food we eat. Our research shows that added sugar should be included on product labels so that consumers can make informed decisions about children’s health.”
For more information about the study, see Obesity magazine and Institute for Responsible Nutrition (IRN).