Australasian Science Magazine

By Stephen Luntz

A connection between sugar consumption and obesity may not seem like news, but a review of 68 studies on the topic has produced results that are likely to influence public health policies.

Claims that sugars, particularly fructose, are toxic have achieved widespread attention in recent years, but Dr Lisa Te Morenga of Otago University’s Department of Nutrition says the evidence to support these claims has been sparse. On the other hand, studies funded by the sugar industry have found no relationship between sugar intake and obesity. “These used constant energy intake, so the low sugar diets had other sorts of calories instead,” Te Morenga says.

The World Health Organization (WHO) commissioned Te Morenga to lead an international study to get to the bottom of the issue. She concludes that sugar reduction has a “small but significant” effect on body weight. On average, participants in the studies Te Morenga reviewed lost 0.8 kg when they reduced their sugar intake, while those that increased sugar consumption gained 0.75 kg. Study length varied from 2 weeks to 8 months, with an average of around 3 months. Te Morenga says that longer programs showed greater effects.

The review, published in the British Medical Journal, investigated free sugars added by manufacturers or present in honey, syrups and fruit juices. Consequently the sugars naturally present in fruit or milk were not included.

Te Morenga says while there may be no calorific difference between the different types of sugars, those in fresh fruit come with plenty of other nutrients, and are rarely consumed to excess. “Sugar in drinks doesn’t appear to have a satiating effect, so if you have a sugary drink with a meal you will eat just as much,” she says.

Te Morenga is now studying the specific effects of fructose, but says at the moment her advice is to cut down on sweetened foods in general rather than worrying about different sorts of sugar.

The work will influence WHO recommendations on sugar consumption, and have given new life to calls for taxes on sugary foods and limits on marketing. Te Morenga supports such calls, arguing: “Foods that are sweetened and have little nutritional benefit shouldn’t be cheaper than those that have nutritional value.”