There is no doubt that Americans have become heavier in recent decades. As a result, we are spending upwards of $40 billion a year on books, products, and programs designed to help us lose weight. But is this money well-spent? Rethinking Thin, by New York Times Health and Fitness reporter Gina Kolata, is an eye-opening examination of the obesity epidemic in the United States. Kolata follows a group of subjects in a University of Pennsylvania study comparing the Atkins diet with a traditional low-calorie, low-fat one. Along the way, she explores the conventional wisdom about dieting, obesity and health, and finds that much of it is contradicted by the evidence. For example:
Overweight individuals have slower metabolisms. False. There is little association between body weight and the rate of metabolism.
Low fat diets promote weight loss. False. It’s all about the number of calories you consume in a day, and the composition of those calories has little effect.
Being overweight is hazardous to your health. Not true. A study by Flegal et al. found that while obesity (BMI>30) and underweight (BMI<18.5) are both associated with higher mortality, the range classified as overweight (25 < BMI < 30) is actually associated with lower mortality than the so-called normal BMI range from 18.5 to 25.
The measures usually advocated to prevent children from becoming overweight are effective. False. Two large studies examined the effects of integrated programs that taught school children about nutrition, provided healthy breakfasts and lunches, promoted regular in-class exercise, and even involved the parents, to try to improve the type of food the children ate at home. The result? Children in schools that received the interventions did reduce their fat intake, but there was virtually no change in weight as compared with children in control schools that had not received the interventions.
I must admit that after reading this book I am more confused than ever about what is a healthy weight and how to maintain it. But I prefer the confusion to the pseudo-science that passes for diet advice these days.
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