The University of Otago-led study is published today in the British Medical Journal, to ringing endorsement from US nutrition experts in an editorial concurrently published in the influential UK journal.
The study’s lead authors, research fellow Dr Lisa Te Morenga from Otago’s Department of Human Nutrition and the Riddet Institute of New Zealand, and Professor Jim Mann from Otago’s Department of Human Nutrition and Medicine and Edgar National Centre for Diabetes and Obesity research, found that there is now enough evidence from the research to show that cutting down on sugar has a “small but significant” effect on body weight.
The WHO has previously recommended that intake of “free sugars” should be less than 10 percent of total energy intake. Free sugars are sugars that are added to foods by the manufacturer, cook, or consumer; plus those naturally present in honey, syrups, and fruit juices.
The WHO asked the Otago-led group to analyse the results of controlled trials and cohort studies of sugar intake and body fatness, and review the evidence on the association between consuming free sugars and body weight in adults and children.
After searching through nearly 8000 trials and 10,000 cohort studies published internationally up until December 2011, the researchers found 68 studies that directly looked at the effects of free sugars on body weight.
The results of this analysis show that reducing free sugars in the diet has a small but significant effect on body weight in adults – an average reduction of 0.8 kg. Increasing sugar intake was associated with a corresponding 0.75 kg increase in body weight.
This parallel effect, they suggest, seems be due to an altered energy intake, since replacing sugars with other carbohydrates did not result in any change in body weight.
The evidence was less consistent in children, mainly due to poor compliance with dietary advice. However, for sugar-sweetened beverages, the risk of being overweight or obese increased among children with the highest intake of sugary drinks compared with those with the lowest intake.
A separate BMJ editorial, from Professor Walter Willett from the Harvard School of Public Health in Boston, and Professor of Pediatrics at the Boston Children’s Hospital David Ludwig, endorses the Otago findings, saying that action should be taken at many levels, including educational programmes, improvement in food and drinks provided at schools and worksites, as well as policy approaches, such as increasing tax on sugar laden drinks.
“Reducing the amount of sugar consumed in drinks deserves special attention because of the strength of the evidence and the ease with which excessive sugar is consumed in this form,” they write.
Dr Te Morenga, Professor Mann and colleagues acknowledge that the extent to which population based advice to reduce sugars might reduce risk of obesity “cannot be extrapolated from the present findings, because few data from the studies lasted longer than ten weeks.”
But conclude that “when considering the rapid weight gain that occurs after an increased intake of sugars, it seems reasonable to conclude that advice relating to sugars intake is a relevant component of a strategy to reduce the high risk of overweight and obesity in most countries.”
“It seems easier to overeat if your diet includes lots of sugary foods and drinks. When you overeat you gain weight,” says Dr Te Morenga.
Also in the BMJ, a feature discusses the 40th anniversary of the publication of the popular book – Pure, White and Deadly – written by the British physiologist John Yudkin, which claimed that high sugar consumption was associated with heart disease.
It considers new evidence linking fructose (found in nearly all added sugars) with insulin resistance – a precursor of heart disease – and suggests that Yudkin’s warnings are finally being recognised, despite ongoing opposition from the sugar industry.
Dr Lisa Te Morenga
Tel 64 3 479 3978
Professor Jim Mann
Currently in Te Anau, Tel 64 3 249 9103
- Full paper: www.bmj.com/cgi/doi/10.1136/bmj.e7492
- Editorial: www.bmj.com/cgi/doi/10.1136/bmj.e8077
- Feature: www.bmj.com/cgi/doi/10.1136/bmj.e7800