Intended for healthcare professionals

Analysis Essay

The science of obesity: what do we really know about what makes us fat? An essay by Gary Taubes

BMJ 2013; 346 doi: https://doi.org/10.1136/bmj.f1050 (Published 16 April 2013) Cite this as: BMJ 2013;346:f1050

Re: The science of obesity: what do we really know about what makes us fat? An essay by Gary Taubes

To suggest as Richard Conrad Cottrell has that from the systematic review and meta-analysis by Morenga et al (1) that there is no link between sugar consumption and body weight seems a tenous oversimplification.

When putting their “Results in the context of existing knowledge” Morenga et al state: “ Widely discrepant conclusions have emerged, ranging from strong or convincing evidence for an association to evidence described as unconvincing or equivocal. This variance is hardly surprising, owing to the poor compliance in most intervention trials, the insensitive instruments used for assessing dietary intakes in cohort studies, and that in such studies, intakes might have changed between initial dietary assessment and measurement of outcome”.

“Nevertheless, we were able to show a consistent effect when comparing groups with the highest intakes of sugars with those with the lowest intakes.”

“However by limiting analyses to ad libitum trials, and considering studies in adults and children separately, our systematic review showed a clear positive association between higher intake of sugars and body fatness in adults, and provided an explanation as to why the findings in children were less conclusive.”

Paige et al (2) have recently provided some basic science support on the differential effect glucose and fructose have on regional cerebral blood flow in brain regions involved with appetite and reward pathways. Cerebral blood flow and activation of the hypothalamus, insula and striatum, the regions of the brain that regulate appetite, motivation, and reward processing was reduced, and was also associated with feelings of fullness, satisfaction and satiety in response to glucose but not fructose ingestion. So does the use of high-fructose corn syrup in processed foods encourage over consumption?

To single out sugar as the sole culprit for increasing obesity levels is probably over simplistic. However given the methodological issues noted by Morenga et al and the positive links found in their analysis in some sub groups between sugar consumption and weight gain, to claim there is no culpability for sugars role in overeating and weight gain is also not an evidentially supported defence.

1) Morenga LT, Mallard S, Mann J (2013 Jan) Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. British Medical Journal 345e7492

2) Page KA, Chan o, Arora J et al (2013 Jan) Effects of fructose vs glucose on regional cerebral blood flow in brain regions involved with appetite and reward pathways. Journal of the American Medical Association. 309(1): 63-70.

Competing interests: No competing interests

04 May 2013
Alan O Szmelskyj
State Registered Osteopath,
True Health Clinics Godmanchester and St Neots
34 Cambridge Road, Godmanchester, Huntingdon, Cambridgeshire PE29 2BT, UK