The arithmetic of weight control has long been understood: we gain weight when we consume more energy (calories) than we burn off (through living, breathing, moving, etc.). We maintain weight when the input and output are equal. We lose weight when we burn off more than we consume. This is simple enough and in today’s world of smart-phones, smart-devices, smart-people, smart-cars, smart…well, you get the idea…it is a bit “old school” and it is not very fashionable. But it is the cornerstone of weight control because this simple arithmetic cannot be avoided and must be embraced if we are to control our weight. It is also true that many weight loss programmes, products and services prefer to avoid this truth because it is so simple (you cannot sell simple for big profit) and unfashionable (it is not “smart”) and hard (these companies know they have to offer something “easy” if they are going to make a sale) but that is really another whole story…..the point is this: if YOU want to control your weight you’re going to have to understand and accept this reality.

What is a calorie?

A calorie (Cal) is a unit of energy (specifically the ammount of energy required to heat 1000g of water by 1 degree celcius, but that is not important here) used when discussing food. The metric unit is a Kilojoule (kJ) and there are 4.2 KJ in 1 Cal. Calories and kilojoules are describing the same thing.

How many calories do I need to eat to lose weight?

This is the big question. the science is a bit complex here and the answer varies a bit depending on your gender, age, activity level, and some other things. But absolute precision is not really needed here because a practical guideline will work for most of us.

  • The average woman needs to consume 2000 calories (or 8800 kilojoules) to maintain her weight. Eating less will usually result in weight loss. A 10-20% reduction is usually recommended so the average woman, looking to lose weight, should consume around 1700 calories (or 7140 kilojoules).
  • The average man needs to consume 2500 calories (or 10 500 kilojoules) to maintain his weight. Eating less will usually result in weight loss. A 10-20% reduction is usually recommended so the average man, looking to lose weight, should consume around around 2100 calories (or 8820 kilojoules).

Younger and more active people living in cold climates may need to eat more. Older and sedentary people in warm climates may need to eat less. The heavier you are the more you do need to eat to maintain your weight. The lighter you are the less you can afford to eat to maintain weight. But as a rough guide, the above will work. There are many online calorie-calculators where you can plug in your particulars and be shown how many calories you need to eat to maintain, gain, or lose weight. Just google…

How do I do this?

This is the tricky part. all of the above is just basic science and some arithmetic, but using this knowledge is really the hard part.

  1. Set your target. Decide how many calories you want to eat per day.
  2. Read food labels. You need to understand how many calories are in the various foods you eat and that information is all on the label. It may be in calories or in kilojoules but either way it is there.
  3. Track your calorie intake. You can use a simple piece of paper or a sophisticated smart-phone app. It doesn’t matter. You will have to weigh your food or estimate its weight because the food labels will just give you “xxx calories per 100g” so you need to know if your portion is 100g or 300g or whatever, and then do the arithmetic (e.g. 200g of a “60 calories per 100g” food is 60 x 200/100 or 60 x 2 = 120 calories).
  4. Be honest.

Too complicated?

The calorie-counting method described above, and there are many variants on the theme of course, is too complicated and time-consuming for many of us. Mercifully there is another approach…

Understanding that you have been gaining weight and noting that you want to lose weight, what you need to do is eat less than you have been. By less we mean fewer calories. To do this you really just have to be honest about what you have been eating, and then reduce (by about 10-20%). A simple food-diary might help here or you could use a smart-phone app. But even without this, most of us know how to eat “less” don’t we?

Is that all there is to it?

Yes. And no. If you can follow one of the methods described above, honestly and consistently, you will lose weight. You must lose weight really (the basic science is that simple and that true). But of course there are many ways to make it easier and many ways to be healthy while doing so. You should, for example:

  • Only set realistic targets (losing 1/4 to 1/2 kg a week or so).
  • Eat fewer carbohydrates and or choose better (high fibre, low GI) carbs.
  • Eat quality proteins like lean meats, eggs, fish, soy and legumes.
  • Avoid sugar and sugary drinks.
  • Drink 1500-2000ml of water each day, especially before meals.
  • Be active.
  • Avoid crash diets and fad diets. You want gradual sustainable weight loss and a balanced diet.
  • Consider your food-habits and look out for triggers like boredom, stress, television, etc.

We are not going to go into detail on all of this here, but we do recommend you do some homework on each of these points.

Weight control really does come down to some simple but powerful arithmetic and eating fewer calories is really the key to losing weight.