Body Fat, Weight Loss and All That

I've been reading The Diet Delusion by Gary Taubes, which I commend to you if you want to know anything about diet and nutrition. It prompted me to think over the whole issue of weight loss, diet and exercise properly.

Let's start with the basics. You eat a 300 gram apple. As a result, you now weigh 300 grams more than you did. The only way you will weigh the same as you did before you ate the apple is to lose 300 grams. How do you do that? Well, what goes in has to go out or be stored. The stores are triglyceride molecules in fat cells or additional bone or muscle mass. What goes out is urine, sweat, faeces and moisture in your breath.

How about losing weight by exercising? Say, walking a mile at about four miles an hour. This will burn roughly 100 Calories. The body stores 7,700 Calories in a kilo of (white) body fat. So you have burned up 64 grams of body fat. The catch is, aside from the sweat you dripped onto the pavement or absorbed in your clothes, you haven't lost any weight yet. The body fat has disappeared in a reaction using oxygen and other chemicals to make various waste products: the mass of the waste products equals the mass of the body fat, oxygen and other chemicals. (To many, many decimal places, chemical reactions conserve mass.) Those waste products are still in your body, so you still weigh the same – this is why you never seem to weigh less after a work-out at the gym. You won't lose the weight until you pass water or faeces. What the exercise does is increase the amount of waste material you pass.

By 64 grams for a mile-long walk. Unless you are an athlete or an infantryman, you will use very little energy by “exercising”: most of your energy use is in your basal metabolic rate – keeping your core body warm, processing food, re-oxygenating blood, making all those cells to renew your body and other such work. For a man, that's about 2,000 Calories a day. Cut down your food intake to 1500 Calories in the right way, so that you burn body fat and you are losing 300 grams a day, or 2 kilos a week. That's how you lose weight without having a Hollywood trainer and all day to exercise.

So how do you make sure you burn the body fat? The answer, Taubes is suggesting, is “carbohydrates drive insulin, insulin drives fat”. Cut down on sugars and starches, your insulin levels go down and your body releases more fat from its cells, which burn up and create more waste products. It also reduces the need for all the water needed to handle carbohydrate-based food processing. A good chunk of weight loss in the early stages of any diet is water being disposed of because it's suddenly become surplus to requirement.

This, at any rate, is how I make sense of what Taubes is saying. I'm trying it right now. The challenge is eating a low (refined-) carbohydrate, low sugar diet while working in an office in central London.