STATS ARTICLES 2010
New York Public School's Whole Milk Swindle
Trevor Butterworth, February 3, 2010
Department of Education says its success in reducing child obesity by removing whole milk from schools can be replicated accross America. What "success"?
How do you measure success? If it's the battle against childhood obesity, it would seem simple: you weigh the kids and keep weighing the kids as you try various interventions to reduce calorie intake or increase calorie expenditure, while controlling for various confounding factors. If the children deemed to be overweight end up losing weight then, not unreasonably, you may claim success.
But this is not the way New York City's Department of Public Education measures the war on childhood overweight and obesity, categories that consume almost 40 percent of the elementary school population.
Instead of monitoring children's weights after removing whole milk from school cafeterias and replacing it with low fat or no-fat milk, it just measured the difference in overall calories entering the cafeteria system and concluded that as the children couldn't eat them, they couldn't turn them into fat, and therefore they were better off.
As an account of this research published in the Centers for Disease Control's Morbidity & Mortality Weekly Report, notes, the researchers "analyzed system-wide school milk purchasing data" and found that children in public schools "were served an estimated 5,960 fewer calories and 619 fewer grams of fat in 2009 than they were in 2004." The Department of Education concluded that "[t]he switch to lower-fat milk likely has improved the overall nutritional environment of NYC public schoolchildren."
But how likely is likely? Did this switch have an actual impact on student weight? We simply don't know. As the researchers themselves admit, "no data were collected on total food consumption during the school day, so the effect of the milk switch on overall diet is unknown. Students might compensate for the averted calories/fat from milk by changing their consumption patterns."
In addition to neglecting substitution effects, the researchers assumed that:
a) whole milk, which accounted for 33 percent of all milk purchases by the Department of Education in 2004 was a key contributory factor to overweight and obesity in New York's public school population.
b) that children who drank whole milk before the ban were overweight or obese (remember, only a third of the milk in the pre-ban school system was whole; who was drinking it and were they more likely to lose weight from switching to low fat milk?)
c) that the continued, robust consumption of sweetened 1 percent or fat-free chocolate milk (accounting for 60 percent of all milk purchases) did not have unintended dietary consequences, given that both contain significantly more sugars than regular milk. In fact, for 1 percent chocolate milk, there is almost the same amount of sugar, gram for gram, as Coca Cola.
The differences between milk purchasing, nutritional environment, actual weight loss, and health outcomes were overlooked in the media coverage.
HealthDay's headline claimed "Students Benefit From Milk Switch: Study." Medpage Today reported that "[w]hen New York City public schools made the switch from whole milk to skim or low-fat milk, students cut their annual fat and total calorie consumption."
The Baltimore Sun claimed that "[t]he numbers get really impressive when you add them all up. For each of NYC's 1.1 million public school students, the switch resulted in 5,960 fewer calories and 619 fewer grams of fat in 2009 compared to 2004." Except it didn't, as these figures only apply to the 63 percent of children who drank milk during the day (and because weight isn't measured, it's still a hypothetical weight loss).
The problem with declaring success on the basis of measuring diminished exposure to calories in a school cafeteria can be illustrated with the following absurdity: In theory, the Department of Education could, by just offering water and vitamins and maybe a few pieces of fruit, solve the obesity crisis entirely.