Body composition explained
It’s become common knowledge that being healthier is about much more than simply losing weight. You may have heard of terms such as ‘body composition’, ‘body mass index’ and ‘body fat percent', but what do they actually mean?
If you’re trying to lose weight, gain muscle or generally become healthier, understanding your body composition can be key to making sure you get on the right track and stay there.
Why measure body composition?
Obesity is a major health concern in the UK. In 2018, a record high of 20% of children aged nine to 11 were classed as obese. Overweight children are more likely to be overweight as adults and are at an increased risk of a various health conditions.
Knowing your body composition gives you a complete picture of your body health and provides insights into areas you need to focus on.
There are plenty of benefits to using body composition scales. For starters, it will motivate you to achieve your health goals. You can find out how much body fat you have and set an accurate and realistic calorie limit for your body. The scales will also allow you to see if you're dehydrated or overhydrated by measuring your body water levels.
If you measure your body composition and find that you have high levels of fat, you could start exercising while measuring body fat percentage and muscle growth.
Total Body Water
- Shows how hydrated the body is.
- Useful for transporting waste, helping organs to function, regulating body temperature and digestion.
- Healthy total body water for men is between 60 and 65%; for women it's between 45 and 60%.
Basal Metabolic Rate (BMR)
- The amount of calories your body needs to function.
- Typically around 1,662 calories for men and 1,393 calories for women.
- Helps you set an accurate, realistic calorie limit for your body.
- Not simply based on generic average male/female/age statistics you would find online.
- Based on how many calories your body would need if it was resting for 24 hours and only needed to support vital functions, such as breathing.
Fat Free Mass
- Everything that isn’t body fat.
- Bone, water, muscle, organs and tissues.
- Metabolically active, meaning they burn calories for energy.
Female vs male healthy body composition
- 12% essential fat
- 15% storage fat
- 12% bone
- 25% organs, water etc.
- 36% muscle mass
- 3% essential fat
- 12% storage fat
- 15% bone
- 25% organs, water etc.
- 46% muscle mass
How to work out your BMI
To calculate your BMI, divide your weight (in kilograms) by your height (in metres), then divide this answer by your height again.
- Below 18.5 You're considered underweight.
- 18.5-24.9 A healthy BMI range for your height.
- 25-29.9 You might be heavier than healthy for someone of your height.
- 30 or more Those with a BMI of more than 30 are classified as obese.
Remember, with excess weight comes an increased risk of heart disease, stroke and Type 2 diabetes.
Limitations of BMI
The NHS considers BMI the best way to quickly assess an adult’s weight, although it’s not without its flaws.
The following factors show why BMI isn’t always the perfect universal assessment of weight:
- Pregnancy Pregnant women naturally gain weight due to their growing baby, so BMI readings won't be accurate.
- Children With children, age and sex need to be taken into account as well as height and weight.
- Muscle Your level of muscle mass isn't taken into consideration with BMI measurements. Particularly active people may be given an inaccurate reading.
- Ethnicity Research has shown that those of south Asian or Chinese descent have an increased risk of developing Type 2 diabetes. Although the evidence is less definite, black people are advised to maintain a BMI below 25 to reduce the risk of developing Type 2 diabetes.
Body composition and smart scales
Smart bathroom scales go beyond basic weight measurements and can give you reports on everything from your body fat percentage, muscles mass and bone density to, water mass, heart rate and even our metabolic age.
Traditional bathroom scales won’t tell you how much of your body is made of fat, water or muscle. You just get one number staring back at you telling you that you’ve either lost or gained weight. You could be exercising five times a week and having salad for dinner just to step on the scale and see that nothing’s changed.
If you’re weighing yourself every day with a normal scale, the number you see is likely to be distorted by fluctuations in weight because of factors such as being dehydrated or having a big lunch. For a good idea of changes occurring over time, weigh yourself once a week at similar times (eg first thing in the morning).
Compared: female and male body fat percentage
There is no universally agreed ideal body fat percentage due to factors such as height, gender and genetics all playing a part.
The below table of body fat percentages by the American Council on Exercise (ACE) is a frequently used reference point.
Female body fat percentage chart
Male body fat percentage chart
According to the World Health Organization (WHO), the healthy body fat range for men aged 20 to 40 is anything between 8% and 19% body fat. The normal range for men over the age of 40 is between 11% and 25%. To be considered obese, a person would have a body fat percentage of more than 30%.
Women generally need a higher body fat percentage than men because it’s necessary for childbearing and oestrogen production. The WHO defines a healthy body fat range for women aged 20 to 40 as being between 21% and 33%, while women over 40 need 23% to 36% body fat. Women with more than 40% body fat are considered obese.
The essential body fat required for maintaining minimum health levels is 5% for men and 8% for women.
Athletes typically have lower body fat levels than the non-athletic population because excess fat may affect their performance.
How to achieve a healthy body fat
Your body is made up of two types of mass: body fat and fat-free mass. ‘Essential fat’ is necessary to stay healthy – it helps protect our internal organs, stores fuel for energy and regulates important body hormones. However, the problem comes when we have an excessive storage of non-essential body fat.
Body fat percentage is a body composition measurement. Bear in mind that not all fat is visible, so you could have more of it than you think. Visceral fat is stored within the abdominal area and surrounds important organs, including the liver, stomach, and intestines. It can also build up in the arteries and increases the risk of serious health problems.
Having a high percentage of body fat can mean that you’re overweight and/or your fitness levels are too low.
Dangers of being overweight or obese
- Type 2 diabetes.
- Coronary heart disease.
- Some types of cancer, such as breast cancer and bowel cancer.
The best way to lose weight is through a combination of diet and exercise. To lose weight at safe rate and have a greater chance of maintaining a lower weight, cut 500 to 1,000 calories from your diet each day as this should help you lose 1 to 2lb a week.
Dangers of being underweight
- Nutritional deficiencies.
- Weakened immune system.
- Fertility problems.
Being underweight could mean you're not eating enough or that you may be ill. Adjusting your calorie intake will help you increase or decrease your body fat levels. To gain weight at a safe rate, increase your calorie intake by 250 to 500 per day.
Information on dangers of being overweight and underweight taken from NHS website.