If you’ve ever stood on the scales and not liked what you’ve seen, here’s a crumb of comfort. 

Truth is, more than half your body weight has nothing to do with what you eat. 

It is actually the weight of parts of your body — from your heart to your muscles and even blood. 

However, these weights may fluctuate even on a daily or weekly basis. And these changes can reflect the state of your health, as this fascinating guide to your body weight reveals…

The truth is that more than half of your body weight is unrelated to anything you may have eaten

Truth is, more than half your body weight has nothing to do with what you eat

Fluid — 40-70% of your body weight

The main reason your body weight changes throughout the day is because of water weight.

‘Around 50 to 70 per cent of a man and 40 to 60 per cent of a woman is water,’ says Abby Coleman, a sports scientist at Precision Hydration. 

So, if you weigh 150lb (68kg) as a man, then 75lb to 105lb (34kg to 48kg) of that could be water; and in a woman of the same weight, it’s 60lb to 90lb (27kg to 41kg).

‘The variation depends on your ratio of muscle to fat, as muscle contains more water, mostly because glycogen [a sugar that is stored as fuel for the muscles] is bound to water,’ she says.

‘That water is then split broadly into that which is outside our cells [known as extracellular fluid, which is the watery part of your blood and the fluid that bathes your cells], and intracellular fluid, which is found within the cells.’

We constantly lose water throughout the day in urine, breath and sweat — and gain it by eating and drinking.

What you eat will also impact how much water your body loses or gains. Cut out carbohydrates and you’ll lose a lot of water weight because you’ll draw on the glycogen stored in the muscles to fuel them. Fluid levels will drop as you decrease these glycogen stores.

Eat more carbs and you’ll replenish your glycogen — and fluid — stores. You will also retain water if you eat too much salt.

‘That’s why you might weigh 4.4lb (2kg) more after a weekend of enjoying alcohol (which contains high levels of sugar and other carbs) than you did the previous Friday,’ says Arj Thiruchelvam, a sports scientist from Performance Physique in Birmingham.

‘But by Wednesday your weight should be back to normal as you would have lost this excess water again.’

Overnight, you continue to lose fluid. In fact, it’s estimated that we can lose 3lb (1.4kg) of fluid a night, which is why it’s suggested you weigh yourself first thing in the morning, as you’re at your lightest.

Blood- 7% 

An average adult’s eight-tenths of a pint of blood makes up 7 percent of his total body weight. That would translate to a 150lb person (68kg) weighing around 10.5lb (4.8kg).

The amount you lose if, say, you cut yourself, isn’t likely to make a notable difference on the scales — but blood donation might. According to the NHS Blood and Transplant service, the average blood donation takes around 470ml (just under a pint) of blood — which weighs around 1.1lb (499g). It won’t stay gone for long, though — your body makes around two million red blood cells per second and it’s estimated that those removed during donation are replaced within 48 hours.

Weight changes during a woman’s period aren’t due to blood loss: the average woman loses just 30ml to 40ml of blood during her period, around 30g to 40g in weight. This is because of fluid retention due to the increase in progesterone hormone pre-menstrually.


Bones — 15%

The skeleton makes up about 15 per cent of your total body weight — so, if you weigh 150lb (68kg), then your bones would account for around 22.5lb (10.2kg) of that.

Interestingly, 25 to 31 per cent of the weight of bones is actually water, and it’s believed it helps nutrients move around the bone.

Calcium and collagen make up the bone marrow and bones.

Big bones are a real thing. Overweight people have more bone mass, and this is because their bodies move more, creating stress which encourages them to grow.

Osteoporosis will cause bones to become less dense and lighter, though it’s unclear by how much.

The skeleton makes up about 15 per cent of your total body weight ¿ so, if you weigh 150lb (68kg), then your bones would account for around 22.5lb (10.2kg) of that

The skeleton makes up about 15 per cent of your total body weight — so, if you weigh 150lb (68kg), then your bones would account for around 22.5lb (10.2kg) of that

Skin — 14%

Our skin makes up a sizable 14 per cent of the body’s weight. Your skin is more important the taller and larger you get. A person weighing approximately 150lb (68kg) will have 21lb (9.5kg) skin.

However, skin regeneration takes place approximately every 28-days. According to an article published in 2011, skin flake loss can range from 28 to 85 grams per hour.

If that makes you feel squeamish, here’s some good news: a type of oil, called squalene, in these skin flakes absorbs the gas ozone in the air. U.S. research from the University of Medicine and Dentistry of New Jersey found that this helps reduce indoor pollution.

Muscles — 40-50% 

40% to 50% of your body weight is made up by muscle mass. Some of this comes from the weight of organs such as the heart and lungs, which are mostly muscle, but the vast majority is in fact skeletal muscle (so-called because it’s muscle mostly attached by tendons to bones of the skeleton) — for example, the biceps, triceps, abdominals and glutes.

It is interesting that the bigger your muscle mass, the heavier you may be, and the smaller your body will appear.

‘Muscle is defined and dense so 2.2lb (1kg) of muscle will spread over a smaller area than the same amount of fat,’ explains sports scientist Arj Thiruchelvam. Your age, sex and exercise levels will determine how much muscle you have.

‘Aerobic exercise — such as running and swimming — will increase muscle in the lungs and heart, whereas resistance exercise — such as lifting weights — also increases skeletal muscle,’ he says.

However, the muscles are more effective at handling exercise and they build less as a result.

‘That’s why you should always challenge yourself,’ he adds.

The more muscle you have, the more you might weigh, but the smaller you will look

You will appear smaller if you have more muscle than you are.


Fat — 11-33%

The body is awash in fat. ‘Its main job is to insulate the body from cold and protect the organs,’ says Arj Thiruchelvam.

Subcutaneous fat is the stuff under the skin — it’s what you can pinch around the arms, tummy, thighs and buttocks.

Visceral fat, which is located around the major organs and can be more dangerous than normal, releases inflammable compounds that are linked to type 2 diabetes, heart disease and possibly some types of cancer.

For the average man aged 40-to-50 years, this is a healthy level of body fat. Above 34 percent is considered obese.

It should be between 23 and 33 percent for a woman this age; over 40 percent is considered obese.

‘The body is in a constant state of flux, and its weight is always being lost or gained,’ explains Arj Thiruchelvam.

Head — 8%

Your parents are responsible for your head size. Nine genes have been identified as being associated with this trait.

But while men’s heads are slightly larger than women’s, on average the adult head — including the skull, brain, teeth and tongue — weighs 12lb (5.4kg). 

Its weight doesn’t change, but certain movements can more than double the load your head places on your neck, causing problems, according to Kenneth Hansraj, a spinal surgeon at New York Spine Surgery and Rehabilitation Medicine.

In a 2014 paper in the journal Surgical Technology International, Mr Hansraj calculated that if you bend forward to look at your phone (or even the scales when weighing yourself), the effect of gravity means it’s like having a weight of between 27lb to 49lb (12.2kg to 22.2kg) on your neck.

You could be at greater risk for neck or shoulder pain if you use your phone too long.

Head size is largely genetic, with nine known genes associated with it, so blame your parents. But while men¿s heads are slightly larger than women¿s, on average the adult head ¿ including the skull, brain, teeth and tongue ¿ weighs 12lb (5.4kg)

The nine genes that are associated with head size have been identified as being genetic. But while men’s heads are slightly larger than women’s, on average the adult head — including the skull, brain, teeth and tongue — weighs 12lb (5.4kg)

Breasts — 3.1%

Research dating back to 1980s suggests that women’s breasts average around 1.06lb (408g) Larger breasts, however, can weigh as high as 4.7lb (2.21kg).

‘It’s hard to weigh an individual breast, so information is limited,’ says Joanna Wakefield-Scurr, a professor of biomechanics at Portsmouth University.

‘But generally, breast weight depends not just on size but on how much glandular matter versus fat each breast contains — glandular tissue [the part that makes milk]The latter is more common. It can also be affected genetically, and it changes with pregnancy.

‘Around 10 per cent of women have breasts almost entirely made of fat, while another 10 per cent have breasts heavily skewed toward glandular tissue.

‘The weight of the breasts can increase in the second half of the menstrual cycle due to fluid retention which is linked to higher levels of the hormone progesterone — one study has suggested the breast volume can increase by up to 40 per cent at this time.’

Studies dating back to the 1980s suggest that the average weight per breast in women is around 1.06lb (480g). But larger breasts can be as much as 4.7lb (2.1kg) each

According to studies dating back from the 1980s, the average breast weight for women is 1.06lb (480g). Larger breasts, however, can weigh up to 4.7lbs (2.1kg).

Gut bacteria — 3%

The collective name for the bacteria and microbes living in our stomach is called the microbiome.

‘It’s recognised that the human body has 100 trillion microbes in the gut — ten times more than there are cells in the human body, and that they amount to perhaps 4.4lb (2kg),’ reported the journal Nutrition Reviews in 2012. 

‘The weight of your microbiome changes daily — but it’s impossible to measure by how much,’ says Dr Federica Amati, a nutrition scientist and research associate at Imperial College London.

‘However, its weight is not as important to health as the diversity of bacteria it contains. In as little as 48 hours you can ensure that healthy microbes crowd out the less helpful ones by adding new types of fibre to your diet.’

The microbiome is the collective name of the bacteria and other microbes that live in our gut

Microbiome refers to the whole group of microbes and bacteria that reside in the microbiome.

Liver — 2%

The liver is the largest gland in the body (a ‘gland’ means it produces hormones) and weighs, on average, 3.97lb (1.8kg) in men and 3.09lb (1.4kg) in women. The liver is made mostly of blood and muscle. Healthy livers should have little to no fat.

Excess alcohol intake can cause a build-up of fat in the liver, as can non-alcoholic fatty liver disease — which affects one in three people.

‘Liver weight increases in fatty liver disease and it can weigh more than 2kg in very severe cases,’ says Professor Nick Sheron at the Foundation for Liver Research in London. ‘Fatty liver can cause issues when the fat content is more than 5-10 per cent, leading to the slow development of scarring.’

A non-alcoholic fatty liver condition is often linked to obesity or other conditions such as hypertension or type 2 diabetes.

Lungs — 1%

Average men’s lungs weigh 1.85lb (880g) and average women 1.41lb (660g), respectively. This accounts for about 1% of their total body weight. Although the right lung is slightly heavier (about 40 to 45g less), it’s divided into three (lobes) while the left lung has only two.

Smokers’ lungs may weigh more than non-smokers’ as a side-effect of immune cell destruction that occurs when the body tries to clear the tar, and other chemicals in cigarettes, from the lungs.

Also, dead cells that contain smoking residue may build up. A similar effect can be caused by high levels of indoor pollution.

Heart — 0.45%

Healthy hearts account for 0.45 percent of your total body weight. A normal male heart is 8oz to 13.5oz, while a female one weighs between 5oz and 10oz (142g-283g).

‘The exact weight will depend on your height, weight, sex and lifestyle,’ says Professor Declan O’Regan, a cardiac imaging specialist at Imperial College London.

The heart gets larger because of exercise. Some athletes see a 20 percent increase in their size due to the fact that they are able to work harder.

‘And we found that just three hours’ exercise a week was enough to increase its size,’ says Professor O’Regan. ‘Endurance training tends to make it larger while strength training makes the heart muscle thicker.’

The other way the heart can ‘gain’ weight is through excessive weight gain, where fat can build up around it — this increases the risk of cardiovascular disease.

Hair — 0.3%

Of course a haircut means you lose weight — but you’re unlikely to notice it on the scales.

Healthline calculates that, depending on thickness of the hair, an average full head would add 6.1-23.0 oz (175cm to 369g).

It’s thought each inch you have lopped off will cause you to ‘lose’ 0.0037oz to 0.00074oz (105mg to 21mg) in weight. You could weigh an extra ounce if you have wet hair. Dry hair weighs between 12-18% more and dry hair about 12-18% less.

Waste — 0.15%

It’s often suggested that you weigh yourself first thing in the morning after using the bathroom, but how much difference can a bowel movement actually make? According to a study by the University of Cambridge in 1992, where researchers weighed stool samples from 220 British adults, the average male stool weighs 3.66oz (104g); in females it’s 3.5oz (99g). So weigh yourself before and after going to the loo and you’ll lose around 3.5oz (99g).

‘Stools typically contain a mix of water, fibre, bile and bacteria from the large intestine, and their exact weight depends on what you’ve eaten and how much. A very large meal rich in fibre will produce a larger stool,’ says Dr Amati.

Although the weight loss from the stool may not be significant on the scales it can make you feel significantly lighter.

Dr Amati says this is because the gut has many nerve endings and when we need to go to the bathroom, we’re receiving a lot of information from them, making us aware of the gut area.

We feel more light-weight when we move a stool. ‘The relief we feel after passing a stool is very helpful in reminding us to go when we need to,’ says Dr Amati.

Eyeballs — 0.01%

They weigh approximately 0.25 oz (7g) and can vary in size between people. The eyeballs do tend to get heavier each year.

Research from Sydney’s Institute for Eye Research found that the average thickness of the eyes increases 1.38mg each year. As the lens becomes thicker, sight decreases. This reduces light entering the eyes and affects focus, leading to presbyopia (and the need for reading glasses). Men’s lenses thicken more than women’s and so their eyes are a tiny bit heavier.

Notice: Note that the total percentage may exceed 100 percent as other elements like water, blood, and muscle could contribute to more than one.