'Healthy' diet = weight gain

Part 3: It's not all about calories

The orthodox Golden Rule for treating overweight is: calories in minus calories out equals weight change. As you will see later, although this hypothesis is plausible and has what looks like umpteen good, solid, rigorous, clinical studies appearing to support it, it is actually quite wrong. However, if we assume it is correct, that brings up the first big problem: How do we answer the apparently simple question: How many calories are there in an item of food?

Despite supermarkets' desire for uniformity, natural food products can vary widely from item to item. An early season fruit, may be much lower in sugar than one from the peak of the season; a green banana is mostly starch, while an overripe one is mostly sugar.

And that is only the first problem. The second is even harder to answer: How much energy do you use when you do something? If you walk a mile you will use less energy than someone else who walks the same distance, but weighs more. If you do it more quickly your energy usage will differ from someone doing it slowly.

With this approach you cannot know how much energy to take in. Neither can you know how much you are using.

When is a calorie not a calorie?

The second Golden Rule of orthodoxy is: 'A calorie is a calorie', whatever its source. This means that if you eat X number of calories more than you use, you will put on Y amount of weight, wherever those calories come from. This again is far from true. In trials, dieters on fat-based diets consistently lose much more weight than dieters on carb-based diets, even when both diets have exactly the same number of calories. Therefore, 'a calorie is a calorie' is not so meaningful after all: a carbohydrate calorie is obviously much more fattening than a fat calorie. This can only mean that some calories don't count as much as others.

There is an emerging scientific consensus that weight control is a highly complex topic and the old ideas that overweight people are lazy gluttons are now realised to be as absurd and insulting as the overweight have always thought they were.