Understanding the role of sugar sources in development of childhood obesity

New research being presented at the European Congress on Obesity (ECO) in Venice, Italy (12-15 May) suggests that the source of sugar is more important than the amount of sugar when it comes to the development of obesity in children.

The study found that the total amount of sugar consumed when very young was not associated with weight at age 10 or 11. 

However, children who got a higher proportion of their sugar from unsweetened liquid dairy products (milk and buttermilk) were less likely to go on to live with overweight or obesity.

Similarly, getting more sugar from fruit was associated with less weight gain. However, getting a lot of sugar from sweet snacks such as cakes, confectionery and sweetened milk and yogurt drinks, such as chocolate milk, was linked to being of higher weight.

The high consumption of sugary foods is considered a risk factor for childhood overweight and obesity and so children are advised to consume less sugar-rich foods, such as confectionery, cakes and sugar-sweetened drinks, and eat more fruit and unsweetened dairy products, such as milk and yogurt."

Junyang Zou, lead researcher of the Department of Epidemiology, University of Groningen and University Medical Center Groningen, Groningen, The Netherlands

"But while fruit and unsweetened dairy products are considered healthy, they contain high amounts of intrinsic sugars – sugar that occurs naturally in the food, rather than being added. We wanted to know if the source of sugar, added versus intrinsic, as well as the amount, affects the likelihood of developing overweight or obesity.

"While this has been studied before, the results are inconsistent and there is a lack of high quality research on the topic."

To address this, Ms Zou and colleagues used data from the GEKCO Drenthe study¹, an ongoing longitudinal study of a cohort of children born in Drenthe, in the northern Netherlands, between April 2006 and April 2007, to explore the association between total sugar intake in early childhood and the intake of sugar from different sources on weight, weight gain and the development of overweight and obesity.

The answers to a food intake questionnaire filled in by the parents of 891 children (448 males) when the children were 3 years were used to calculate daily total sugar intake and the daily sugar intake from 13 food groups [vegetables; fruits (whole fruit only); cereals; starchy vegetables; nuts; legumes; meat, eggs, vegetarian meat substitutes, and oil, butter, and margarine; milk and milk products; coffee and tea, and coffee and tea-based drinks; sugar-sweetened beverages (including fruit juice, lemonade and sweetened milk and yogurt drinks); savory products including homemade and ready meals and soup; sugary snacks such as cakes, confectionery and chocolate; toppings/sauces/sugars].

Height and weight, as measured by trained nurses, were used to calculate BMI Z-scores, the change in this score between 3 and 10/11 years and weight status at 10/11 years (normal weight/overweight/obese, as defined by International Obesity Task Force 2012 criteria).² 

BMI Z-scores are a widely used measure of weight in childhood and adolescence. They show how a young person's BMI compares to the average BMI for their age and sex, with higher values representing a higher weight.

All 891 children were included in the BMI-Z score at 10/11y and change in BMI-Z score analyses. 817 of the children (414 males) were included in the weight status analysis (74/891 were living with overweight or obesity at age 3 and were excluded from this analysis).

Average total daily sugar intake was 112g. This made up around a third (32%) of the total daily energy intake of 1,388 calories. 

The main sources of sugar were fruit (average daily intake = 13g), dairy products (18.6g), sugar-sweetened beverages (41.7g) and sugary snacks (13.1g).

At 10/11 years of age, 102 children with normal weight at the age of 3 had developed overweight or obesity. 

Total sugar intake at 3 years was not related to BMI Z-score, weight gain or weight status 10/11 years.

However, a higher intake of sugar from sugary snacks was related to a higher BMI Z-score at 10/11.

In contrast, a higher daily sugar intake from fruit (whole fruit only) was related to a lower BMI Z-score at 10/11 years and less weight gain. (No significant association was found between fruit juice and weight.)

And a higher sugar intake from unsweetened liquid dairy products (milk and buttermilk) was related to a lower odds of developing overweight/obesity at age 10/11. Children with the highest intake of these products aged 3 had a 67% lower risk of going on to have overweight/obesity, compared to those with the lowest intake.

The study didn't look at why these foods affected weight differently. However, possible explanations include slower release of sugar from pieces of fruit than from sugary snacks and differences in how the sugars in the different foods (sucrose in cakes and confectionery, fructose in fruit and lactose in dairy) act on the body.

The researchers conclude that when it comes to developing obesity in childhood, the source of sugar seems to be more important than the amount. 

Ms Zou adds: "Children should be encouraged to have fruit and milk instead of sweetened milk and yogurt drinks, sweets, cakes and other foods rich in added sugar."