A calorie is simply a measurement of energy. But it's also the source of confusion and worry for many people trying to lose weight. At the same time, calories -- too few or too many -- are causing health problems resulting from malnutrition and obesity that affect billions of people around the world.
A new 304-page book, "Why Calories Count: From Science to Politics" (University of California Press), aims to clear up the confusion. It explains in accessible language what calories are and how they work, biologically and politically. Its authors are Marion Nestle, a visiting professor at Cornell and professor of nutrition, food studies and public health at New York University, and Malden Nesheim, professor emeritus of nutritional sciences at Cornell.
Nesheim and Nestle take readers through issues that are fundamental to understanding diet and food, including weight gain, loss and obesity and misinformation put forth by food manufacturers and diet program promoters.
Calories, the authors write, also affect societies in political and personal ways.
The authors not only explain how scientists count calories in food and measure how bodies use them but also why we need calories for survival, warmth and work, covering metabolism and how the body uses calories. They also discuss calorie needs, the difficulties of estimating calorie intake and the body's complex weight management system.
In exploring issues related to too few calories, they discuss starvation, global hunger and whether restricting calories could prolong human life. Their section on too many calories covers obesity, the complex relationship between calories and weight gain, whether all calories are created equal and whether some kinds of diets work better than others.
Having armed readers with the necessary information to interpret food labels, evaluate diet claims and understand evidence as presented in popular media, Nesheim and Nestle elucidate the political stakes and show how federal and corporate policies have come together to create an "eat more" environment. Finally, the authors offer some candid advice: Get organized. Eat less. Eat better. Move more. Get political.
"Ultimately, the calorie is political: marketing affects instinct, and Nestle and Nesheim really shine in their analysis in this realm," wrote Mark Bittman in a New York Times' "Opinionator" blog March 20.
Nesheim is co-author of (with Nestle) "Feed Your Pet Right: The Authoritative Guide to Feeding Your Dog and Cat" and of (with Ann L. Yaktine) the Institute of Medicine's report "Seafood Choices: Balancing Benefits and Risks."
Explore further: Is fructose being blamed unfairly for obesity epidemic?