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Work out your ideal weight

Did you know?

If you eat more food than your body needs, the extra energy will be stored as fat and you will put on weight. (Some people either don't know this, or won't acknowledge it)

News in a hurry

  • Body weight is determined by kilojoules in vs kilojoules out.
  • To lose weight – eat less, move more.
  • Abdominal fat is more dangerous than fat on hips and thighs.
  • To gain weight – eat more from a nutritious balanced diet.
  • Aim for 30 minutes exercise every day.
  • Generally speaking, 20-25 is a healthy BMI.
  • Women should aim to have waists <88cm, and men <102cm.
  • Being overweight or underweight can cut your life expectancy.

Weight control

If the kilojoules you take in each day are equal to the kilojoules you use up - your weight will stay the same. Most people maintain a constant body weight in this way, without even thinking about it. If the kilojoules you take in each day are more than the kilojoules you use up – your weight will rise.

New Zealand wins bronze medal in obesity!

A Health Care Data 2009 report, by the Organisation for Economic Co-operation and Development, found that New Zealand is the third fattest nation in the developed world. The obesity rate among adults in New Zealand in 2007 was 26.5%, compared with figures reported the previous year by the United States at 34.3% and Mexico at 30%.

But the good news is we are starting to recognize the dangers of this and want to do something about it.

If the kilojoules you take in each day are less than the kilojoules you use up – you will lose weight. Traditional weight loss programmes, like Weight Watchers and Jenny Craig, are based on this. We take in kilojoules by eating and drinking, we use up kilojoules by moving our bodies.

It is much harder to lose weight by exercising than by reducing the amount of high energy foods you eat each day, eg, it takes 1 hour of brisk walking to use up the amount of kilojoules in just one croissant! The combination of healthy eating and exercise offers the most benefits. There is nothing mystical about this, it really is simple science.

What is, for some people, terribly more complex, is the relationship between what and how much we eat and how much exercise we take, how we think about what we eat and do, and what affects those relationships, thoughts and actions.

How to work out your ideal weight

Body Mass Index (BMI)

The most widely accepted method to assess weight is body mass index. It determines whether your weight is putting you at risk, and is based on your height and weight.  

Your ideal weight - that at which you are at least risk - depends on your build, age, how muscular and fit and how tall you are. One of the quickest ways of calculating a healthy weight is to work out your body mass index (BMI) by dividing your weight in kilograms by your height in metres squared (kg/m²). BMI = kg/m²

The normal weight BMI range is 18.5 to 24.9.

Work out your BMI

  • Measure your height in cm and divide by 100 to get m.
  • Measure your weight in kg.
  • Divide your weight by your height in m².

BMI Calculation Example

  • Height: 1.63m
  • Weight: 65kg
  • BMI =  weight divided by height x height  =  65 divided by 2.67 = 24

The BMI measure is designed for men and women between the ages of 18 and 65 years.

  • A score below 18.5 indicates that you may be underweight.
  • A healthy BMI score is between 18.5 and 25.
  • A value above 25 for a NZ European or 26 for a Maori or Pacific Islander indicates that you may be overweight.
  • Your risk of health problems rises significantly from a BMI of 27 to anything over 30 (32 for Pacific people), which is a serious health concern.

If you have concerns about your weight you should mention it the next time you visit your doctor.

Try our quick BMI calculator

Take care using BMI – it is only a guide! Be aware that BMI guides can be misleading; BMI tends to relate to fat mass on the body but, for active or more muscular people, BMI may overestimate this. Plus, people of Asian origin tend to carry a higher fat mass for a given BMI, and those of Polynesian origin have a proportionately lower fat mass for a given BMI.

Waist circumference

Another check for healthy weight is to measure your waist. Women with a waist of over 88cm and men with one of more than 102cm are at much greater risk of disease than those with smaller measurements.

Waist-to-hip ratio or WHR

Some researchers believe WHR is a better predictor of heart attack risk than BMI. In New Zealand the WHR is used as a screening tool to find people at risk.

To calculate WHR, measure your waist at its smallest point and your hips at their widest. Divide the first number by the second: for men, a healthy WHR is under 1; for women, it's under 0.8, according to the National Institute of Diabetes and Digestive and Kidney Diseases in the US. The higher the ratio, the higher the health risk.

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