So Mayor Bloomberg was on the right track

Sugar and Obesity

From: Andy Soos in ENN.com

Excessive sugar in the diet has been linked to obesity, and a higher risk of chronic diseases. The most consistent association has been between a high intake of sugar sweetened beverages and the development of obesity, but not all studies have reported a statistically significant link.

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 Center 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.

Studies on the link between sugars and diabetes are have been excessive amounts of sugar does not increase the risk of diabetes, although the extra calories from consuming large amounts of sugar can lead to obesity, which may itself increase the risk of developing this metabolic disease.

Sugar remained relatively unimportant until the Indians discovered methods of turning sugarcane juice into granulated crystals that were easier to store and to transport. Crystallized sugar was discovered by the time of the Imperial Guptas, around 5th century AD. Indian sailors, who carried clarified butter and sugar as supplies, introduced knowledge of sugar on the various trade routes they traveled.

The World Health Organization has suggested that intake of free sugars should be less than 10% of total energy intake, but no upper safe limit has been agreed. So a team of researchers at the University of Otago and the Riddet Institute in New Zealand analysed the results of 71 studies (30 randomised controlled trials and 41 cohort studies) of sugar intake and body fatness to summarise evidence on the association between intake of dietary sugars and body weight in both adults and children. Free sugars were defined as sugars that are added to foods by the manufacturer, cook, or consumer; plus those naturally present in honey, syrups, and fruit juices.

Differences in study design and quality were taken into account to minimise bias. They found that advice to reduce free sugars was associated with an average 0.8 kg reduction in weight (in studies that ran for up to 8 months), while advice to increase intake was associated with a corresponding 0.75 kg increase.

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.

The evidence was also less consistent in children, mainly due to poor compliance to dietary advice. However, for sugar sweetened beverages, the risk of being overweight or obese increased among children with the highest intake compared with those with the lowest intake.

The authors say that, given the many causes of obesity, it is unsurprising that the effect of reducing intake is relatively small, and they point out that some other unmeasured (confounding) factors may explain some or all of this effect. But they add the overall consistency of the findings, regardless of study type, is reassuring. 

They also 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. 

In an accompanying editorial, US experts say the association between sugar and poor health has remained contentious over the past few decades, but that accumulating evidence "points towards a role for sugar and other refined carbohydrates in the development of overweight." They say reducing the intake of sugar sweetened drinks "is a high priority" and point to policies such as taxes on sugar laden drinks, restrictions on advertising to children, and limits on serving sizes.

So sugar does have high calories and as might be expected helps to lead to obesity.

For further information see Sugar Intake.