Health threat of sugar
The US study finds that a ‘calorie is not a calorie’ sparking a controversy.Ron Antonelli/Bloomberg via Getty Images

Sugar is a bigger threat to health than generally believed, a study by a Robert Lustig, paediatric endocrinologist in the US, has found. It says sugar causes metabolic diseases whether we put on weight or not.

The test saw 43 obese children aged between nine and 18 replace sugary food for starchy food. Next, their added sugar consumption was reduced from 28% to 10% and fructose from 12% to 4% of the total calories. Doing so, within 10 days, the test reportedly saw the health of the children improve while still consuming the same amount of calories as before the test.

After the test, the children's metabolic diseases such as blood pressure, "bad" LDL cholesterol, triglycerides and blood glucose dropped significantly. Also, the insulin levels were cut by a third and their liver function had improved.

"The results are not convincing to me – this is a very small study, and it has not been statistically well-controlled," professor of metabolic medicine at Glasgow University, Naveed Sattar, said. "Also, when people are losing weight, even if modest, their metabolic changes can seem larger than they actually are – one needs to see results once folk return to their habitual state after they've finished losing weight. Overall, this study is of modest interest but is far from convincing."

The study, which was published in the journal Obesity, says "a calorie is not a calorie", which many scientists have disagreed with as they have stressed that the calorific content in sugar alone can be damaging to one's health. The test was carried out at the UCSF Benioff children's hospital in San Francisco and Touro University, in the state of California.

Professor emeritus of nutrition and dietetics at King's College London, Tom Sanders, said the study had to be viewed "with some scepticism", as "it is just inconceivable that isocaloric substitution of sugar from starch would have such a large effect on metabolism. In fact it denies the basic laws of thermodynamics", Sanders was quoted as saying by the Guardian.

He further said the study did not compare children in the same age group who consumed a high-sugar diet. Instead, the comparison was made on the weight and health of the children who were on their normal diet before the study began.