In a letter to the editor, Dr Brendan O’Sullivan has espoused the benefits of the low carbohydrate diet at the expense of a low fat eating program promoted for weight loss, thus questioning programs such as the GutBuster program. As the developer of this program and a medical educator in obesity, I feel this requires a reasoned response for medical practitioners to avoid throwing out the baby with the bathwater.
Dr O’Sullivan is right to suggest the low carb diet is a resurrection of the Atkins diet, which was discredited more than 25 years ago. In hindsight it is obvious that this is with good reason. However, before this is spelt out, it is important to stress that fad diets come and go, usually not lasting more than 6-12 months. There is a very good reason for this and that is that any reduction in total energy - whether through carbohydrate, protein or fat - resulting in a negative energy balance will result in weight loss over the short term. However, it is now well accepted amongst obesity researchers that weight loss for less than 12 months is not regarded as effective. Anyone can lose weight. Keeping it off is a different matter. The low carbohydrate diet fails in this latter category.
Although all ‘diets’ should be condemned (because they can’t be maintained) the low carb diet has particular problems and can be argued against on several different levels. In the first instance, carbohydrate is the most accessible form of energy. While one dietitian may claim that a low carbohydrate diet provides ‘more energy’, there is ample evidence that over the long term, it will increase lethargy and result in a decrease in energy and hence ability to carry out that which has the most long term benefit for weight loss, ie. regular physical activity. It requires more energy to store carbohydrate as fat in the body (25%) than it does to save fat as fat (3%). Fat is also known to be less satiating and lead to passive over-consumption. A diet that is high in fat (and many high protein and/or low carbohydrate diets qualify here because fat is often more accessible in animal protein) can lead to dyslipidaemia in individuals prone to this.
One also has to look to expert opinion. Of the four sets of national clinical guidelines for obesity currently in existence throughout the world, none recommend a low carbohydrate diet, while all recommend a low fat pattern of eating. As an NH&MRC committee member currently developing guidelines for Australia, I can guarantee that we will follow suit on the basis of scientific evidence. It’s appropriate also to note that at no international conferences on obesity have any low carbohydrate diet exponents ever appeared to present their evidence for this – despite an open invitation to do so from the International Association for the Study of Obesity. Finally, in the US Weight Control Registry, a highly respected research outlet on long term weight loss losers, it is relevant to note (Am J Clin Nutr) that almost all those who have lost weight and maintained this over five years have done so through a low fat eating plan. Virtually none have used a low carbohydrate diet.
Dr O’Sullivan is wrong to suggest that low fat eating (not a diet per se) has proved “spectacularly unsuccessful”. At the individual level they are slower to work than the low carb approach where weight loss is an immediate outcome (because of the fluid loss from reducing carbohydrate), but of much greater success over the long term. If Dr O’Sullivan is using obesity at the population level and self reported fat intake as a measure of lack of success (as has been claimed by some in the US), he would do well to note that despite the claims in dietary questionnaires that fat has been decreasing in the American diet, this is only relative to total food intake. A recent paper by Dr Bob Jeffreys’s group at Minnesota has shown using food disappearance data, that carbohydrate consumption (and total energy) in the US has increased by 35% from 1970-94, while fat consumption has increased by only 5%. Nobody would ever suggest that total energy is not an issue in obesity whether it comes from carbohydrate or fat!
As misinformation in weight control is more counter-productive than in many other fields of health, it is incumbent upon the medical profession to avoid the traps of popularism. I hope the new Australian clinical guidelines on obesity due out later this year will help medical practitioners in this respect.
Garry Egger is the adjunct professor of health sciences, Deakin University, the founder and scientific director of GutBusters, and an NH&MRC committee member currently developing clinical guidelines on obesity for Australia.
Ed note: This article is in response to a letter to the editor called In defence of low carb diets.
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