The basic maths of weight loss

Nutrition is a complex science based on chemistry and physics. And what with pounds, stones, calories and percentages, there is a fair bit of advanced mathematics thrown in as well.

Fortunately, you only have to understand a few key numbers to improve your odds of shedding a large number of pounds.

Brush up on your basic weight loss maths and get ahead of the game with our handy guide.

1. The energy equation

Understanding this simple equation is fundamental to losing weight. It is the basis of our weight loss and maintenance programs. What you have to understand is energy in versus energy out.

Our bodies need a constant supply of energy to function. We take in the energy stored in food and drink and then our bodies convert it into our own energy through the amazing biochemistry of digestion, nutrient transportation and energy metabolism.

• If we ingest the same amount of energy as we use each day, then we are in ‘energy balance’. Our weight remains stable.
• If we ingest more energy than our bodies can use, then we have a ‘positive energy balance’. We store the excess as fat. We gain weight.
• If we burn up more energy through normal functioning and physical activity than we ingest, then we create an ‘energy deficit’. Our bodies draw upon our fat stores to provide the extra energy. We lose weight.

2. Counting calories

Calories (also known as kilojoules) are a measure of how much heat is released in our bodies when we convert food energy into our own energy.

2lb of body weight on the scales contains approximately 1.4lb of fat. Each gram of fat is worth 9 calories.

If you want to lose 1lb to 2lb of excess body fat each week, you have to reduce your daily calories by 450 to 900. That is 3150 to 6300 calories over the course of one week.

Dieters frequently underestimate how much they eat and overestimate how active they are. The only way to be sure is to keep a record.

Use your online diary at least 4 or 5 times a week to log your daily calories. Our graphs and charts allow you to see immediately if you have created an energy deficit today.

Biggest Loser Club tip: Don’t forget you can log into your diary with your smart phone at biggestloserclub.co.uk/m/ when you are on the go.

3. Food labels

The energy-in part of the energy equation begins in your shopping basket. But once you are at the supermarket it is worth remembering that the health claims on the packaging are often misleading and cannot be trusted. For the full story you have to read the labels.

You don’t have to worry about all the numbers and values on the labels. Here are the main points to remember.

• Quantity per 100g

The manufacturers list the ingredients in order of the most to the least by weight, so a quick glance gives you the main ingredient. If sugar is first, then you may want to leave the product on the shelf.

• Energy

The energy content is usually given in kilojoules. The higher the number: the more energy dense the product. Select products with a low energy density for weight loss.

• 1 calorie = 4.2 kilojoules

If you are a maths whizz (or if you have a calculator on your smartphone), you divide the kilojoules by 4.2 (kilojoules ÷ 4.2 = calories). If you want a rough rule of thumb for calculating the sum in your head, halve the number of kilojoules and then halve again.

• Salt

The NHS recommends eating less than 6g of sodium (a component of salt) each day. Most of us eat each much more than that. To keep your sodium levels in the healthy range, select products with 120mg of sodium or less per 100g.

Read more here about the risks of eating too much salt.

• Sugar

Sugar is most people’s favourite treat. As long as you sustain a calorie deficit, you do not have to eliminate it from your diet entirely. The Biggest Loser Club recommends a maximum of 90g per day. Select products with less than 15g of sugar per 100g.

Read more here about how to change your palate and crave less sugar.

• Fibre

The recommended daily requirement for fibre is around 30g, but most of us each much less than this. Dietary fibre fills you up, as well as promoting a healthy gut, and is a valuable component of a sound weight loss plan. Select products with more than 7g of fibre per 100g.

• Saturated fat

This is listed on the label under Total Fats. The Biggest Loser Club recommends a maximum daily intake of 24g per day. Select products with less than 2g per 100g.

4. Burning off extra calories

The energy-out part of the energy equation can be increased by activity and exercise. If you wish to eat more calories, be prepared to do more exercise to sustain your daily calorie deficit.

Here is how much running it would take to burn off these favourite treats.*

Food	Calories	Duration (mins)
Pret a Manger sausage roll (1 serve, 150g)	482	60
Takeaway chicken tikka masala (1 serve, 200g)	314	39
McDonalds quarterpounder, large fries and medium soft drink	1150	144
Mars Galaxy Ripple (1 serve, 33g)	174	22

*Based on a 30 year-old woman, 5 foot 4 inches, 12 stone, running at 1 mile per 10 mins