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LETTERS: Des Spence Childhood obesity and consumption of fizzy drinks: Diet is not that important in obesity BMJ 2004; 329: 54 [Full text]

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re: Diet is not that important in childhood obesity.

Blake B Graham   (2 July 2004)

Non-exercising pigs

Robert A. Da Prato   (2 July 2004)

From anecdotes to evidence

Carrie Helen Ruxton   (8 July 2004)

re: Diet is not that important in childhood obesity. 2 July 2004
Blake B Graham, Student, Curtin University Perth, Western Australia, 6005 Send response to journal: Re: re: Diet is not that important in childhood obesity.	This article unbelievably states “Childhood obesity is not caused by diet but by a lack of exercise pure and simple.” No doubt exercise is extremely important and can attenuate, to some degree, the effect of junk food on weight gain, but it is ridiculous to say that childhood obesity is not caused by diet. This report un-scientifically uses anecdotal evidence to suggest this connection. Are there any studies comparing energy consumption of children from present day to that of the 1970’s?? While obesity has numerous influences, generally obesity is a disorder of excess intake of energy relative to energy expenditure. Children do not become obese through lack of exercise alone, they come obese due to excess intakes of total energy, fats, and high glycemic load meals, genetic influences on metabolism (e.g. fat oxidation, leptin levels, relative BMR) and lack of exercise. The influence of exercise on energy balance is less than that of diet. If children where not eating such bad diets, the majority would not become obese despite a lack of exercise. Regards, Blake Graham, BSc (nutrition) student Competing interests: None declared
Non-exercising pigs 2 July 2004
Robert A. Da Prato, Medical Officer Military Entrance Processing Station, 7545 NE Ambassador Place, Portland OR 97229 Send response to journal: Re: Non-exercising pigs	As a perennial and avid non-exerciser for, oh, 30 years and during this time retaining a medium, non-obese build, I would provide a dueling anecdote to the good doctor. I recall reading a US Yearbook of Agriculture article published sometime in the 1940's and having to do with how to fatten penned pigs -- important to the farmer because of being paid per pound. The article related that high protein and high saturated fat kept these pigs lean, even without exercise. What porked them out was carbohydrate (e.g. corn) and polyunsaturated fats, just the things I believe that increase the propensity of humans to become overweight. Polyunsaturated fats, as products of the seed oil industry and therefore novel, in an evolutionary sense, to our diet, are not only carcinogenic and immunosuppressive (they can be used to prevent transplant rejection) they also(from a physiologist friend of mine)reduce metabolic rate by apparently inhibiting the proteases responsible for converting T4 to T3, the active form of thyroid hormone. Maybe they do or maybe not, but they do make pigs fat by some mechanism. And the amount of such fats has been increasing in our diets for decades, from virtually zero 100 years ago to a substantial portion of our caloric intake today. As for exercise, I suspect Dr. Spence is somewhat of an ideologue because of what he fails to say, namely the morbidity, if you will, of exercise. He's not alone, of course. Several years ago in the US it was reported that 8 high schooler died in that year alone, and that was only from injuries sustained just from high school football. The report didn't mention, spinal cord injuries, joint sprains, broken bones, eye damage, repetitive concussions...there's a long list. Psychologists debate endlessly over the downsides of organized (by adults) compulsory competitive sporting events for children for the lessons they teach. And why subject any child to their loony, hysterical parents on the sidelines. Other than obeying the Common Law, I am opposed to compulsory or forbidden anything since I don't like to ram my ideas down other people's throats nor do I want others to do that to me (so go ahead and eat polyunsaturated fats if you want to; I avoid them,along with exercise, but I might be wrong). There's a lot of wisdom in the bumper sticker: "Eat right, exercise regularly, and still die." Competing interests: None declared
From anecdotes to evidence 8 July 2004
Carrie Helen Ruxton, Obesity Strategist Tayside Health Board Send response to journal: Re: From anecdotes to evidence	While anecdotes provide light relief, the evidence on causes of obesity is clear (less so, the evidence on treatment and prevention). National dietary surveys in the UK show a decrease in total energy, percentage energy from total fat and per capita sugar consumption since the 1970s to the present day. Some argue that under-reporting of food intake has skewed these results but they are the best we have at the moment. National surveys of activity show that we are expending less energy through work, travel and leisure time. That fits with the mechanised, car- oriented, sedentary leisure-loving society that we all recognise. Epidemiology has linked high energy dense diets and high fat diets to obesity. In reality, high fat diets tend to be more energy dense than low fat diets. Interestingly, high sugar diets are correlated with a lower BMI than low sugar diets. Evidence from studies of overweight people shows that, while they have a higher total energy expenditure (because of their larger body mass), they engage less in physical activity. This doesn't tell us much about what they did before gaining weight. However, work on 'at risk' children, i.e. those with one or more overweight parent, suggests that they are less active outwith school, watch more TV and sleep longer. The bottom line is that lack of physical activity is probably the main causative factor in the obesity epidemic. However, I do think high energy density diets contribute and can hamper treatment and prevention unless physical activity is routinely vigorous. Competing interests: Dr Ruxton is also a freelance nutritionist working with a range of food and weight management companies.