Understanding Your BMI

 

BIO-IMPEDENCE FURTHER INFORMATION

Some Salter scales use BIA (Bio Impedance Analysis) technology which passes a small electrical impulse through the body to distinguish fat from lean tissue. The electrical impulse cannot be felt and is perfectly safe. Contact with the body is made via stainless steel pads or a conductive film on the scale platform. This method simultaneously calculates your personal weight, body fat, total body water, BMI, Basal Metabolic Rate, bone mass and muscle mass, giving you a more accurate reading of your overall health and fitness.

CAUTION : Do not use BIA function if you have a pacemaker or other medical device fitted. If in doubt, consult your doctor.

Salter scales are for domestic use only. Pregnant women should only use the weight function.

BODY FAT - WHAT DOES IT MEAN?

The human body is made up of, amongst other things, a percentage of fat. This is vital for a healthy, functioning body - it cushions joints and protects vital organs, helps regulate body temperature, stores vitamins and helps the body sustain itself when food is scarce. However, too much body fat or indeed too little body fat can be damaging to your health. It is difficult to gauge how much body fat we have in our bodies simply by looking at ourselves in the mirror. This is why it is important to measure and monitor your body fat percentage. Body fat percentage gives you a better measure of fitness than weight alone - the composition of your weight loss could mean you are losing muscle mass rather than fat -you could still have a high percentage of fat even when a scale indicates 'normal weight'.

 

 

*Source: Derived from: HD McCarthy, TJ Cole,T Fry, SA Jebb and AM Prentice: "Body fat reference curves for children". International Journal of Obesity (2006) 30, 598-602.

**Source: Derived from: Dympna Gallagher, Steven B Heymsfield, Moonseong Heo, Susan A Jebb, Peter R Murgatroyd, and Voichi Sakamoto: "Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index1-3". Am J Clin Nulr 2000;72:694-701.

The Body Fat % ranges published are for guidance only. Professional medical guidance should always be sought before embarking on diet and exercise programs.

BODY WATER -WHY MEASURE IT?

Body water is the single most important component of bodyweight. It represents over half of your total weight and almost two thirds of your lean body mass (predominantly muscle). Water performs a number of important roles in the body: All the cells in the body, whether in the skin, glands, muscles, brain or anywhere else, can only function properly if they have enough water. Water also plays a vital part in regulating the body's temperature balance, particularly through perspiration. The combination of your weight and fat measurement could appear to be 'normal' but your body hydration level could be insufficient for healthy living.

 

 

***Source: Derived from Wang & Deurenberg: "Hydration of fat-free body mass". American Journal Clin Nulr 1999, 69 833-841.

The Body Water % ranges published are for guidance only. Professional medical guidance should always be sought before embarking on diet and exercise programmes.

For those using Athlete Mode: note that athletes may have a lower body fat range and a higher body water range than shown above, depending on their type of sport or activity. Body water measurement results are influenced by the proportion of body fat and muscle. If the proportion of body fat is high, or the proportion of muscle is low then the body water results will tend to be low. It is important to remember that measurements such as body weight, body fat and body water are tools for you to use as part of your healthy lifestyle. As short-term fluctuations are normal, we suggest you chart your progress over time, rather than focus on a single days reading.

WHY SHOULD I KNOW MY MUSCLE MASS?

According to the American College of Sports Medicine (ASCM), lean muscle mass may decrease by nearly 50 percent between the ages of 20 and 90. If you do not do anything to replace that loss, you are losing muscle and increasing fat. It is also important to know your muscle mass % during weight reduction. At rest, the body burns approximately 110 additional calories a day for each kilo of muscle gained. Some advantages of gaining muscle mass include:

• Reversing the decline in strength, bone density and muscle mass that accompanies age
• Maintenance of flexible joints
• Guide weight reduction when combined with a healthy diet.

 

BONE MASS -WHY MEASURE IT?

Regular exercise and a balanced diet can help maintain healthy bones. Like muscle, bone is a living tissue that can respond to exercise by becoming stronger. For most people, bone mass peaks during their thirties. After that time, we can begin to lose bone. Regular exercise can help prevent that loss. Calcium and vitamin D contribute to healthy bones. Good sources of these are dairy products, green leafy vegetables and fish. The bone mass readings given by this product are an estimation of the amount of bone in your body. Those with osteoporosis or low bone densities may not get accurate estimations. If you have concerns regarding your bones you should always consult your doctor.

WHAT DOES MY BMI VALUE MEAN?

Body Mass Index (BMI) is an index of weight-for-height that is commonly used to classify underweight, overweight and obesity in adults. This scale calculates your BMI value for you. The BMI categories shown in the chart and table below are recognised by the WHO (World Health Organisation) and can be used to interpret your BMI value. Your BMI category can be identified using the table below.

 

 

IMPORTANT: If the chart/table shows that you are outside of a 'normal' healthy weight range, consult your doctor before taking any action. BMI classifications are for adults (age 20+ years) only.

BASAL METABOLIC RATE (BMR) - WHAT DOES IT MEAN?

Your Basal Metabolic Rate (BMR) is an estimation of the energy (measured in calories) expended by the body, at rest, to maintain normal body functions. This continual work makes up about 60-70% of the calories the body uses, and includes the beating of your heart, respiration, and the maintenance of body temperature. Your BMR is influenced by a number of factors, including age, weight, height, gender, dieting and exercise habits.

 

QUESTIONS & ANSWERS

How exactly is my body fat and water being measured?

This Salter Scale uses a measurement method known as Bioelectrical Impedance Analysis (BIA). A minute current is sent through your body, via your feet and legs. This current flows easily through the lean muscular tissue, which has a high fluid content, but not easily through fat. Therefore, by measuring your body's impedance (i.e. its resistance to the current), the quantity of muscle can be determined. From this, the quantity of fat and water can then be estimated.

What is the value of the current passing through me when the measurement is taken? Is it safe?

The current is less than 1mA, which is tiny and perfectly safe. You will not be able to feel it. Please note however, that this device should not be used by anyone with an internal electronic medical device, such as a pacemaker, as a precaution against disruption to that device.

If I measure my body fat and water at different times during the day, it can vary quite considerably. Which value is correct?

Your body fat percentage reading varies with body water content and the latter changes throughout the course of the day. There is no right or wrong time of the day to take a reading but aim to take measurements at a regular time when you consider your body to be normally hydrated. Avoid taking readings after having a bath or sauna. Following intensive exercise, or within 1-2 hours of drinking in quantity or eating a meal.

My friend has a Body Fat Analyser made by another manufacturer. When I used it, I found that I got a different body fat reading. Why is this?
Different Body Fat Analysers take measurements around different parts of the body and use different mathematic algorithms to calculate the percentage of body fat. The best advice is not to make comparisons from one device to another, but to use the same device each time to monitor any change.

How do I interpret my body fat and water percentage readings?

Please refer to the Body Fat and Water tables included within this document. They will guide you as to whether your body fat and water reading falls into a healthy category (relative to your age and sex).

What should I do if my body fat reading is very 'high?

A sensible diet, fluid intake and exercise program can reduce your body fat percentage. Professional medical guidance should always be sought before embarking on such a program.

Why are the body fat percentage ranges for men and women so different?

Women naturally carry a higher percentage of fat than men, because the make-up of the body is different being geared towards pregnancy, breastfeeding etc.

What should I do if my water percentage reading is 'low'?

Ensure that you are regularly taking sufficient water and work towards moving your fat percentage into the healthy range.

Why should I avoid using the Body Analyser Scale whilst pregnant?

During pregnancy a woman's body composition changes considerably in order to support the developing child. Under these circumstances, body fat percentage readings could be inaccurate and misleading. Pregnant women should therefore only use the weight function.