A Calorie is a Calorie: The Inescapable Science that Controls Our Body Weight

By Keith Frayn

A leading expert on fat metabolism explains why ‘calories in versus calories out’ really is the key to living healthily and beating the obesity crisis

We all know someone who seems to eat very little yet cannot avoid weight gain or, conversely, someone who eats cakes and ice cream while remaining slim. Then there are those who argue that it’s not calories that count, but what kinds of foods we eat and how our hormones and other body signals control our energy intake. Some even claim that environmental chemicals are fuelling the obesity crisis. Many people, including specialists, are questioning whether we have the correct understanding of the forces that shape our body weight.

Enter Keith Frayn, one of the world’s leading experts on metabolism. Taking readers on a deep dive into the science of energy balance, he reveals why it is unlikely that some nutrients are intrinsically more fattening than others, how supposed differences between people in the speed of their metabolism vanish in the laboratory, how energy balance is altered in people suffering from obesity as well as those who have managed to lose significant weight, and why these responses – honed over millennia of evolution – make dieting so hard. With robust science and a clear-eyed perspective on the latest diet and nutrition fads, he argues that the only way of addressing the obesity problem is by rebalancing the ‘calorie equation’.