No such thing as just a spoonful of sugar: new research on eating too much of it and its links with weight gain

There’s been plenty of the white stuff in the news over the weekend. It’s everywhere, affecting every household. Most of us love it, a few of us hate it, and it poses risks to our health. Yes, I’m talking about sugar! It’s been discussed in the House of Commons, as the PM David Cameron fessed up to struggling to stop his children drinking lots of sugary drinks and Labour MP Keith Vaz reminded the House of the large quantities of sugar consumed in this way by the nation’s schollchildren, a third of whom are obese or overweight by the time they leave primary school.

Nothing new in concerns about sugar and its implications for our health, of course, but  a new piece of research on the link between sugar and body weight was published in the British Medical Journal last week, which brought together randomised controlled trials (RCTs) and prospective cohort studies on this topic in a systematic review and meta-analysis. The revewiers conducted extensive searches of appropriate databases, supplemented by handsearching, and found 30 RCTs and 38 cohort studies suitable for inclusion. Trials of weight-loss or where there were additional medical or lifestyle interventions were excluded. Here’s what they found:

  • In trials with adults with no strict control of food intake, reduced intake of dietary sugars was associated with a significant reduction in body weight and increased sugars was associated with a comparable increase in body weight
  • Trials with children found low compliance with dietary advice to reduce intake of sugar sweetened food and drink and showed no overall change in body weight, but…
  • …after a year of follow-up in prospective studies, those with the highest sugar intake were more likely to be overweight than those with the lowest sugar intake
  • Replacing dietary sugars with other macronutrients with the same energy value resulted in no weight change
  • These trends were consistent and the associations remained when studies at high risk of bias were excluded from the analysis
  • Results from cohort studies were generally comparable with trial findings
  • Limitations of the study include shortcomings in the data provided on dietary intake and variation in the nature and quality of the dietary intervention

The authors conclude that, amongst free living people with no strict control of food intake, “intake of free sugars [defined by the WHO as all monosaccharides and disaccharides added to foods by the manufacturer, cook, or consumer, plus sugars naturally present in honey, syrups, and fruit juices] or sugar sweetened beverages is a determinant of body weight”. They go on to say:

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. However, 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.

The BBC report picked up on the finding that replacing sugars with macronutrients with the same energy values was not associated with weight gain and the suggestion that one piece of the jigsaw of how sugar intake can lead us to pile on the pounds is that we take in more energy this way than we use up. Some researchers argue that sugar is addictive, including the University of California’s Professor Lustig, quoted in the BBC report, who’s in no doubt about how seductive the stuff is: “You can make dog poop taste good with enough sugar”. We might not go that far, but I think most of us agree it tastes good and I certainly find that the more I eat it the more I want it. It feels like time for a little something right now, but after reading this I’m going to make sure I choose something virtuous.

Links:

This open access article can be downloaded in full:

Te Morenga L, Mallard S, Mann J. Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ 2013;346:e7492

BBC News 20th January 2013. How addictive is sugar?

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Sarah Chapman

My name is Sarah Chapman. I have worked on systematic reviews and other types of research in many areas of health for the past 17 years, for the Cochrane Collaboration and for several UK higher education institutions including the University of Oxford and the Royal College of Nursing Institute. I also have a background in nursing and in the study of the History of Medicine.

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