Earlier this month I blogged about some research which suggests that being overweight is not the dire threat to our health and longevity it is so often assumed to be. One reason why the risk of being overweight may be somewhat overstated has to do with the fact there’s a lot of money in persuading people that they should be lighter than they are. In particular, the food and pharmaceutical industries stand to do well out through the sale of weight loss drugs and ‘diet’, ‘lite’ and ‘low-fat’ foods that make an implicit weight loss promise.
I take a generally dim view of foods that have been manipulated in a way that supposedly gives them advantages to would-be slimmers. Such foods are generally sold on the basis that fat is inherently fattening (which studies suggest it is not) or that artificial sweeteners induce weight loss compared to sugar (also unproven).
The drugs used to treat excess weight come in a variety of forms. The main players are:
Orlistat (trade names Xenical and Alli) which blocks the digestion of fat
Sibrutamine (Reductil, Meridia) which is an appetite suppressant
Rimonabant (Acomplia) which limits the absorption of fat from the digestive tract
The effectiveness of these drugs with regard to weight loss was assessed this week in a study published on-line in the British Medical Journal (BMJ) . The review looked at the available evidence from studies in which these drugs had been compared with placebo.
The results revealed that the average weight loss attributed to the orlistat, sibutramine and rimonabant were 2.9 kg (4.6 lb), 4.2 kg (9 lb) and 4.7 kg (10.5 lb) respectively.
The study also found that 30-40 per cent of individuals defaulted from their treatment. One reason for this, of course, is that individuals may have got the impression that what they were taking was not having the desired effect. Another reason relates to the fact that these medications are not without side-effects. For instance, rimonabant is associated with an increased risk of anxiety and depression. While orlistat is associated with, amongst other things, ‘oily leakage’ from the anus.
What is more, the weight loss effects of these drugs was generally regarded by the authors of this review as modest. The loss of 5 kg equates to less than 5 per cent of the total body weight. The authors note that the National Institute for Health and Clinical Excellence (NICE) here in the UK recommend that if a drug does not lead to a loss of at least 5 per cent of body weight within 3 months then it should be stopped.
Another issue concerns the fact that while these drugs may bring weight loss and even other apparent benefits (e.g. orlistat is associated with a reduced risk of diabetes), we don’t actually know what the effects these drugs have on broader measures of health and risk of mortality.
Taken as a whole, the evidence we have available suggests that weight loss drugs have limited benefits for individuals. Add to that the increasing evidence which suggests that carrying ‘excess’ weight is not nearly as hazardous as we have been led to believe, and we might question what place such weight loss drugs have in medical practice.
1. Rucker D, et al. Long term pharmacotherapy for obesity and overweight: updated meta-analysis. BMJ. 2007 Nov 15 [Epub ahead of print]