Low carb diets – science or fiction? (English verson)

Due to popular demand (from at least one person), here is an English version of my post about low carbohydrate diets.

The above video points out a mismatch between the promises presented in various low carb diet books and the authors’ own weight and appearance. But there is no need to resort to personal slurs or American presidential election style tactics in order to criticise these diets, an in depth look at the books themselves, and the theories and scientific foundation presented, provides plenty of ammunition.

When I did my Masters degree in sports science some ten years ago the current low carb craze had just begun. When choosing a topic for my first dissertation I therefore decided to take in depths look at some of these diets, amongst them Dr. Atkins’ Diet Revolution by Dr Robert Atkins, and The Zone by Barry Sears. After reading these books I attempted to evaluate the scientific foundation by retrieving as many studies as possible from the references, and by searching various scientific databases for research published by the authors, or research carried out on these, or similar, diets. More generic search terms like ”causes of obesity”, ”carbohydrates and obesity” , “ketogenic diets” etc were also used. Here are some of my findings:

  • When searching for studies published by Dr Atkins and Sears on their diets I could not find a single research paper published by them. They present theories as if they are absolute truths, but seemingly without going through the process of scientific studies, peer reviews, or publication. Sears even makes several references to his own research in his books, complete with p-values, but without listing these studies in the reference section. Why is this research not publicly available? Has he chosen not to publish his research because he knows it is too poor to withstand scrutiny by other scientists? Or has he tried to publish, but been refused due to poor quality? Has he even done the studies he refers to?
  • Several of the researchers Sears references have publicly distanced themselves from The Zone diet, saying that Sears is misusing their work. Some of them have even contributed to a leaflet warning the public against this diet (Riley, 1999). The studies Sears bases his allegations on have been carried out mainly on animals and cell cultures, and the results of these studies may therefore not be generalisable to humans.
  • When I tried to retrieve the studies Dr Atkins referred to I discovered that several of the studies simply did not exist. More than once I retrieved the correct journal, volume, and pages, only to find a completely different study there. In other cases the studies had been published in journals so obscure it was not possible to find them, despite having access to Europe’s largest collection of medical journals at the Royal Society of Medicine in London. Was this due to sloppiness and typos by Dr Atkins when writing up the references, or intentional fabrication, done in the belief that no one would bother to check?
  • Those studies I did manage to find were often old, mostly from the 1950s, with very few subjects (typically 2-10), and without a control group. As with the research used by Sears, the results from these studies are not generalisable to the population as a whole.
  • According to Dr Atkins, you can eat unlimited amounts of calories on his diet and still lose weight. However, the few studies that have been done on Atkins-type diets indicate that this is a good old fashioned low calorie diet, with some subjects reducing their energy intake by as much as 55 %. (Probably due to the limitation of foods one is allowed, and the fact that high calorie foods such as chocolate, candy, biscuits, chips, ice cream etc are banned.)
  • One of the goals of the Atkins diet is to induce a state called ketosis, in which fatty acids, ketones, from the body’s adipose tissues are mobilised to provide energy. This is an evolutionary defence mechanism enabling us to survive famines. When the amount of fatty acids in the blood stream increases the blood pH drops, and if too low can lead to serious health effects such as loss of consciousness and coma.  The body can stabilise the blood pH by excreting ketones in the urine, which according to Atkins represents a significant energy loss, thus leading to weight loss. Other sources dispute this, saying that the urinary energy loss from ketosis is at most 100 Kcal pr day (McArdle et al, 2001, Riley). To put this in perspective, it takes a negative energy balance of 7000 Kcal in order to lose 1 kilo of body fat.
  • Dr Atkins advises his followers to ignore negative health effects such as dehydration, nausea and fatigue, saying that these are merely carbohydrate withdrawal symptoms. This advice is downright dangerous –fatalities from the Atkins diet have been documented.
  • Both Dr Atkins and Sears recommend a high number of nutritional supplements in order to maximise the benefits of their diets (many of which they just “happen” to sell). By my calculations, if you are to take absolutely all the supplements mentioned by Dr Atkins you will be popping around 100 pills a day. Is this healthy? Natural? Necessary?  The answer to the last questions is yes, as these diets puts their followers at risk of malnutrition due to most or all grains, fruit, and vegetables being banned. Vitamin C, E and K, calcium, magnesium, folate, as well as fibre supplements will at least be necessary to remain healthy.  If the diets recommended by Atkins and Sears are as optimal as the authors claim, why is it then not possible to obtain all the necessary nutrients through the diet alone?
  • There are also several examples of factual mistakes in The Zone. E.g. one can eat at most 1700 Kcal pr day – this is the upper limit for athletes and very active individuals, persons who probably have an actual energy need of 2500-5000 (or more) Kcal pr day. Sears claims that the body’s fat stores will provide the rest of the energy needed, that these stores are virtually limitless. This is not correct; one’s body fat percentage can become too low for the body to function normally. Fat is also not the optimal energy source during high intensity activities, as the process of breaking down fat is very slow compared to when carbohydrates are metabolised.
  • According to Sears we should limit our omega 3 fatty acid intake, and instead aim for a high intake of omega 6 fatty acids. This is supposed to reduce inflammation in the body. All other literature says the opposite; if the intake of omega 6 in relation to omega 3 becomes too high this will increase the production of arachidonic acid (AA). AA is linked to increased inflammation, high blood pressure, auto immune diseases, heart problems, type 2 diabetes, and certain cancers (Vesanto and Melina, 2011). However, Sears also recommends supplementing one’s diet with fish oils, i.e. omega 3, thus contradicting himself.
  • Epidemiological studies tend to show a negative relationship between carbohydrate intake and body weight, and vice versa for fat. People with high intakes of carbohydrates, especially whole grains, fruit, and vegetables, also tend to have higher fitness levels.

In conclusion: a statement is not necessarily true just because it is printed in a book. If something sounds too good to be true, then it probably is. Dr Atkins’ Diet Revolution and The Zone Diets at first give the impression of being logical and scientifically sound, but if you take an in depth look at them you discover these books to be full of errors.

Referances:

Atkins, RC: Dr Atkins new diet revolution. London:Vermillion, 1999

Davis, B, Melina, V: Becoming Raw. The Essential Guide to Raw Vegan Diets. Summertown, TN: Book Publishing Co, 2010

Mauland, MN: The effects of high-protein low carbohydrate diets on health and exercise performance. Submitted in part fulfilment of the requuirements for the degree of MSc Sports Science (Fitness and Health), Department of Biological Sciences, University of Essex, 2001

McArdle, WD, Katch, FI, Katch, VL. Exercise Physiology: Energy, Nutrition and Human Performance, 5th Edition. London: Lippcott, Williams  & Wilkins, 2001

Riley, RE: Popular Weight loss diets: health and exercise implications. Clinics in Sports Medicine. 18(3): 691-701

Sears, B: The Zone. New York: ReganBooks, 1995

Sears, B: The Zone Diet. London: Thorsons, 1999

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