# Counting calories

Are you happy with your body? Would you live on baby food to change it? The UK diet industry is worth £1 billion a year, and new diets appear all the time. While some people are feeding themselves tiny servings of food every 13 minutes to try and speed up their metabolism, others guzzle endless protein shakes to try and bulk up a figure they think is too skinny. But the truth behind losing or gaining weight is just one simple equation:

Energy difference at the end of the day = Energy in (as food) – energy used (in exercise or just in living)

If the energy difference is positive, your body has some extra at the end of the day and stores it, for future use, as fat. If the energy difference is negative, your body needs to find some extra energy from somewhere and takes it from your fat reserves.

So, if you want to lose weight, you should aim to use up more energy than you take in. If you want to gain weight, it’s the other way round. People who have a big energy demand – eg athletes and dancers – need to keep the balance even by making sure they eat enough food to fuel their activities. If it’s so simple, why are there so many diets? Let’s look at the numbers.

### Counting calories

When talking about food, people usually use the calorie as a unit of energy. If you look on the back of a packet of food, you’ll see that this is actually the kilocalorie, or kcal. On the other hand, in science we talk about energy being measured in joules. There are 4.186 joules to a calorie – you might have to convert between them. One kilogram of fat contains 7500 kcal. To burn that off, you’d have to run 75 miles! On the other hand, you could put on a kilogram of fat by eating seven large Big Mac meals.

People in different cultures want different things from their bodies. In Japan, sumo wrestling is a highly respected profession. Great weight is an advantage in a sumo competition.

Many sumo wrestlers weigh more than 150 kg, and consume 20,000 calories a day to maintain this! However, their diet, like most Japanese food, is very healthy – vegetables, rice, broth, meat and fish. It’s the vast quantities that they eat that piles on the pounds. The high protein content builds high-density muscle, while the beer they wash it down with creates a ‘beer-belly’ of fat.

At the other extreme, many Western women aspire to having a figure like fashion models. Models typically weigh only 50 kg and consume about 1300 calories a day, which is mostly made up of protein and vegetables.

Nearly all healthy eating is about eating the right amount of calories for the amount of exercise you do and the weight change you want. No matter what diet you’re on – low-fat, low-carb, or low-chewing – they all come down to that one compact equation. And that’s the skinny.