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Tuesday, October 30, 2012

Dolly Parton and the art of dieting

Sometime back in the early 1990s or thereabouts, Dolly Parton was being interviewed by the famous BBC chat show host, Michael Parkinson. When asked about what diet she used to keep her figure, she replied: “Honey, if you want to lose weight, get your head out of the slop bucket”.  In other word, just eat less. No truer words were ever uttered in the vast realm of advice on dieting. This year we have seen a number of scientific papers published on sugar sweetened beverages, some designed to boost weight gain and some designed to induce weight loss, all adding to the belief that sugar sweetened beverages are both the cause and the cure for modern obesity. A recent paper from the Department of Nutrition at Harvard will help put things in perspective, but only for those wishing to have an accurate perspective.

The first [1] of the sugar papers looked at four groups each given 1-liter of a beverage per day for 6 months. Group 1 receiver a liter of regular sugar sweetened Coke. Group 2 were given a liter of semi-skimmed milk with an approximate equal calorie level to the Coke. Groups 3 and 4 respectively received 1 liter of diet Coke or water. According to the authors, the consumption of the energy-containing beverages led to a compensation effect with a reduction in the intake of other foods and no overall change in energy intake. No dietary data are provided in the paper but 1 liter of regular Coke would have diluted out its equivalent caloric value from all other foods, leading to a reduction in the intake of the latter by 430 calories per day. This Coke group showed a significant accumulation of fat in the liver compared to others but we will never know if it was due to the absurdly high total intake of sugars (about double the normal according to my calculations) or to a reduction in the intakes of micro-nutrients associated with 430 less food than normal every day. Coke for example, does not contain, the B-vitamin riboflavin, but low riboflavin status will lead to increased blood pressure, and the authors did see a rise in blood pressure with regular Coke. 

So, 1 liter of Coke per day did not lead to weight gain ( for example a 1.3% gain with Coke and a 0.8% gain with water). However, two studies reported in the New England Journal of Medicine show that if sugar sweetened beverages in children are replaced with a calorie free version, then weight loss does occur [2]. These studies will be widely cited as evidence that sugary drinks cause obesity. In fact, these studies simply show that if you do as Dolly Parton says, and simply eat less, you will lose weight so the weight loss could have been with any caloric source, not just sugar-sweetened beverages.

Which brings me to the Harvard paper [3]. This study (a subset of a larger dietary intervention) looked at how variation in the distribution of calories in a weight loss regimen influenced weight change and also changes in body composition. Four dietary treatments were used and an energy deficit of 750 kcal per day was the target for each participant. The diets varied the level of fat, protein and carbohydrate. At 6 months, the average amount of fat lost was 4.2 kg and the loss of lean tissue was 2.1 kg.  About half of this fat loss was due to loss of fat from the abdominal fat with about a third lost from subcutaneous fat. Only 0.1 kg of fat was lost from the liver but this represented a loss of 16% of liver fat. There were no differences in any of these measures according to the composition of the weight reduction diets, again, upholding the Dolly Parton rule.

In summary, the first study tells us that if you oblige subjects to eat a 1-liter bottle of regular Coke every day, you won’t gain weight because you reduce your intake of other foods keeping energy intake constant. The second tells us that extracting calories from children’s diets will lead to a weight loss, in this case using sugar sweetened beverages as the target food. The third tells us that Dolly Parton was correct. It really doesn’t matter what the composition of your weight reducing diet is so long as the caloric restriction operates.

So for what its worth, here are my basic rules about successful dieting:

1.      Never start a diet until you have though about it long and hard given that the relapse rate of weight loss is so high.
2.      Never start a diet until you have built physical activity into your daily routine. Physical activity will reverse the negative effects of obesity such as poor glucose management, higher blood pressure and elevated blood lipids.
3.      Don’t diet on your own. Join a weight loss group and get the benefit of the social network of dieting and maintaining weight loss. 
4.      Heed Dolly Parton and just eat less and eat according to your preferences

[1] Maersk M et al (2012) Amer J Clin Nutr 95 (2) 283
[2] de Ruyter et al (2012) New Engl J Ned 367 (15) 1397
[3] de Souza RJ et al (2012) Amer J Clin Nutr 95 614

Monday, October 22, 2012

A bad day at the lab for GM reserach

During this summer, I recall reading in the Sunday Times that the environmental NGOs are beginning to re-think their strategy on GM foods. I see some evidence that this is the case since I cannot find any mention of the following paper on any of their websites: Séralini et al (2012) “Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize”[1]. The publication of this paper has led to the greatest backlash by the scientific community that I have seen in 4 decades in this business. Essentially, Séralini published a paper showing that rats exposed to a GM food (maize) and a herbicide (which is used with the resistant GM crop) developed breast tumors significantly faster and to a greater extent than controls rats over 104 weeks (2 years). The most significant critic is the European Food Safety Authority (EFSA), which is the independent body charged with protecting consumer health in the EU and which is the judge, on the consumers’ behalf, of all scientific publications on food safety including those on GM technology.

The authors used Sprague-Dawley rats that will naturally develop tumors over their lifetime irrespective of any dietary or other treatment and the authors did not discuss the implications of this natural tendency to tumor development for their study. They also used 10 rats per treatment, which according to OECD protocols is adequate for standard 90-day toxicity studies. Monsanto’s submission to EFSA on the GM maize (NK603) used only 10 rats per treatment, but it was for a 90-day toxicity study. However, Séralini’s study was over a “lifetime” and the OECD guidelines recommend the numbers now be increased to 20 per treatment for chemical toxicity tests but that for carcinogenicity studies, this should be increased to 50 per treatment. In an article on this topic, Nature contacted Harlan Laboratories who supplied the rats and were told that for this strain of rat, only 33% of males and 50% of females live to 2 years. According to the OECD protocols, if a study is to last 104 weeks, then the survival rate should be 50% at least and that then 130 rats (half male half female) should be used per treatment.

The lead author apparently agrees that more rats per treatment would have boosted his statistical power but according to Nature[2], he argues that he did not design the study to find tumors.  If at this stage you are confused, then you’re normal!!!

Further criticism from EFSA includes the fact that no information is given on the composition of the rat diets and that no data is given on how much of the herbicide was consumed through its route, drinking water. No data are given on lesions that were found which were not tumors or dropout rates and reasons for dropouts. In addition, the EFSA working group state that the statistical techniques used were not “commonly-used statistical methods” and that the authors do not state whether the unusual statistical techniques they used were, in fact, the a priori choice and if so, why so? Finally EFSA requested the basic data from the authors to examine these shortcomings and they were refused access. Trust is hard won but easily lost. 

If all that wasn’t bad enough, Nature reports on a very sinister dimension to this saga, which has not received widespread attention. According to their correspondent, Declan Butler, the author orchestrated a very tight media offensive that included a film and his new book (Tous Cobayes: OGM, Pesticides, Produits Chimique: All Guinea Pigs, GMOs, pesticides and chemicals) on the work. A select group of journalists were invited (not from Nature) to preview the paper and were asked to sign a confidentiality agreement demanding total secrecy until formal publication. A breach of the terms of the confidentiality agreement would require, according to Nature, the following: “A refund of the cost of the study of several million euros would be considered damages if the premature disclosure questioned the release of the study”. I’m in the wrong business I believe!!!!

The Ethics Committee of one of France’s most august academic bodies Centre National de la Recherche Scientifique described the PR exercise as “inappropriate”.

Who’d like to be the first to write a review of his new book on Amazon[3]? Well although I would, it would be so slanderous that I could not ever afford the libel fee I’d have to pay.

[1] Séralini GE, Clair E, Mesnage R, Gress S, Defarge N, Malatesta M, Hennequin D, de Vendômois JS. Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize. Food Chem Toxicol. 2012 Nov;50(11):4221-31

Sunday, October 7, 2012

Fat Englanders ~ 200 years ago

(Apologies for non-publication of some recent blogs but China still poses Internet challenges)

William Wadd, born in London in 1776. He was from a medical family and he followed in that tradition, becoming a Member of the Royal College of Surgeons of England in 1801. After a distinguished career in medicine, he was appointed one of the Surgeons Extraordinary to King George IV in 1820. Wadd wrote notes on his favourite topic, obesity and although he always proposed to tidy them up for into a book, they were in fact published in unedited form in1816. His book (still available on Amazon) bore the lengthy title: ”Cursory Remarks on Corpulence, Or, Obesity Considered As A Disease: With a Critical Examination Of Ancient And Modern Opinions, Relative To Its Causes and Cure.”  What is singularly important about this book is its comments on obesity and its prevalence, its perceived causes and consequences and on its social context all at the turn of the 18th century. For those of us interested in obesity all of 2 plus centuries later it is worthwhile reflecting on some of the comments of Dr Wadd.

Epidemiology: Of the general epidemiology of obesity prevailing at the time he writes: ”If the increase of wealth and the refinement of modern times, have tended to banish plague and pestilence from our cities, they have probably introduced the whole train of nervous disorders, and increased frequency of corpulence”.  He goes on to argue that: ”It has been conjectures by some that for one fat person in France or Spain, there are an hundred in England.” These comments on the widespread prevalence of obesity 300 years ago is in direct conflict with a key assumption of Robert Kessler in his popular bestseller “An end of overeating” is that obesity is more or less a recent phenomenon…. A measure of opulence that surprises one at first but on reflection should not surprise us at all is the advent of chimneys. Wadd cheekily ponders the adornment of houses with chimneys but speculates that there is no associated record “…of the front of a house or the windows being taken away to let out, to an untimely grave, some unfortunate victim, too ponderous to be brought down the staircase”!

Genetics: “The predisposition to corpulency varies in different persons. In some it exists to such an extent, that a considerable secretion of fat will take place not withstanding strict attention to the habits of life and undeviating moderation in the gratification of appetite. Such a predisposition is often hereditary”. It is interesting to note that 300 years ago there was recognition that obesity had a genetic dimension, which modern research shows to be of the order of 75% in terms of heredity but which is still so hard to stomach for the high priests of health eating.

Social class and the obesogenic lifestyle: “Yet even such dispositions [hereditary] seem to require certain exciting causes to bring them to action. Of these, a free indulgence of the table is principal. For it must be admitted that the lower orders of society, the poor and the laborious are seldom thus encumbered and it is only among those who have the means of obtaining the comforts of life, without labour, that excessive corpulency is met with. You may see an army of forty thousand foot soldiers without a fat man. And I affirm, that by plenty, and rest, twenty of the forty shall grow fat.”

Comments on causes: ”The article of drink requires the utmost of attention. Corpulent persons generally indulge to excess; if this be allowed every endeavour to reduce them will be in vain”. Boo-hoo for the boozers! On sugar he wrote: ”Negroes in the West Indies get fat at the sugar season” and he also commented: “The following case, which occurred in my knowledge, seems to prove how readily the saccharine particles of vegetables contribute greatly to increase bulk”. He then goes to describe a case history of a brewer who got fat, not on the alcohol but on the “sweet wort” from which it was brewed.

Treatments: He describes very many treatments from vegetarianism (the most popular), the consumption of vinegar or soap, salivation, perspiration, exercise or bandaging. He concludes: ”These are the principal articles that have been resorted to in the treatment of this disease; and the person who depends solely on the benefit to be derived from the use of any of them, will find himself grievously disappointed”.

“How can a magic box of pills,
Syrup, or vegetable juice,
Eradicate at once those ills,
Which years of luxury produce”

200 hundred plus years and nothing much has changed!!