SIZE really does matter - a new U.S. study has found that men with smaller testicles are more likely to be involved in childcare. The researchers from Emory University in Atlanta suggest that lower levels of testosterone may suppress a man's mating efforts, allowing him to channel all his energy into nappy-changing, feeding and nurturing.
Here, we look at some other parts of the body and reveal what their dimensions say about your health . . .
SMALL EARS:
Eczema, kidney disease
Neat little ears may be attractive, but they could make you more prone to eczema.
'Small ears often mean small ear canals [the tube running from the outer to the middle ear], which gives you a greater chance of developing eczema of the ears,' says George Murty, consultant ear, nose and throat surgeon at University Hospitals Leicester.
'Your ear canals are lined with skin and, just like skin on the outside of the body, it flakes off.
'It should be shed out of the ear hole and disappear, but with small canals it's harder for the body to shed it, so it tends to be retained. That can give rise to a terrible itch inside, irrespective of whether you have eczema elsewhere on your body.'
Known as otitis externa, this condition is extremely common.
There is also a link between small ears (specifically the outer, visible ear called the auricle) and underdeveloped kidneys.
'If you have small, very low-set ears, below the level of your eyes, it often indicates you have kidney problems.
No one knows why, but you might lack one, have two fused together, or get kidney disease later in life,' says Mr Murty.
LARGE TONGUE:
Sleep apnoea
This could mean you're more prone to obstructive sleep apnoea, a condition that causes interrupted breathing during sleep and affects around 4 per cent of middle-aged men and 2 per cent of middle-aged women in Britain.
As Mr Murty explains: 'If you've got a big tongue or big tonsils, these can flop backwards and block off the airway while you sleep. If it's mild, you snore. But as it becomes more severe, you have periods where you stop breathing - some as long as 30 seconds.'
A small, receding jaw bone can also play a part because the tongue is attached to the jaw.
If the jaw is too far back, the tongue is more likely to block the airway.
The sudden drops in blood oxygen levels associated with sleep apnoea can increase blood pressure and put pressure on the cardiovascular system.
BIG HIPS
Memory loss
The dreaded pear shape has been linked with menopausal brain fog.
Researchers at Northwestern University in Chicago studied the body types and memory test scores of nearly 8,750 postmenopausal women aged 65 to 79, and found those with more weight around the hips had lower scores.
The theory is that fat may contribute to cognitive problems by restricting blood flow to the brain
. However, Nitu Bajekal, consultant obstetrician and gynaecologist at Barnet Hospital, urges caution when interpreting the results.
'The study found that all women with a raised body mass index - above 30-31 - tend to have lower cognitive function.
And in that sub-group, those with bigger hips seemed to score worse. But it was just a snapshot and we don't know if they went on to have cognitive decline.' Yet it's not all bad news.
If you tend to store fat around your hips rather than around your middle, you could be better protected against diabetes and heart disease, because research suggests it's the apple-shaped who are more at risk of these.
LONG FINGERS
Prostate cancer, depression
The length of a man's fingers can hint at his risk of prostate cancer. Scientists at the University of Warwick and the Institute of Cancer Research compared the hands of 1,500 prostate cancer patients with those of 3,000 healthy men.
They found men whose index finger was longer than their ring finger were significantly less likely to develop the disease.
It's thought being exposed to less testosterone before birth leads to a longer index finger - and may protect against the disease (which is fed by testosterone) later in life.
A study at the University of Alberta found that men with a more typically feminine finger length - a relatively long index finger compared to ring finger - were also more likely to be depressed, suggesting depression is associated with lower levels of testosterone in the womb.
Meanwhile, a 2001 study at Liverpool University found children with autism had extremely long ring fingers compared to their index finger - a feature associated with high levels of testosterone before birth.
LONG TOES
Foot disease
If your second toe is longer than your big toe, it could put you at risk of a painful foot condition.
David Houlihan-Burne, a consultant orthopaedic surgeon at the Three Rivers Clinic in Middlesex, says: 'A long second toe means you may develop Freiberg's disease.
It gives you pain when walking because the end of the metatarsal [a bone in the foot] dies off as a result of abnormal forces. It's very common.'
Treatments include steroid injections to ease the pain, or surgery. But relatively long toes compared to the rest of your foot could be an advantage if you want to take up sprinting. Mr Houlihan-Burne says:
'Sprinters have a stronger, more elastic push off with the toes. And long toes make the overall length of the foot bigger, which means longer contact with the ground, which is where the acceleration happens.
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SLIM THIGHS
Heart disease
Ashamed of your wobbly thighs? Take heart from a Danish study of nearly 3,000 men and women, which found that people with thinner thighs had a higher risk of heart disease and premature death.
Researchers thought low muscle mass in the area could be to blame, as it could affect insulin sensitivity.
Meanwhile, researchers at Oxford University have also suggested that fat in the thighs, hips and buttocks traps fatty acids from food, preventing them from floating through the bloodstream and getting deposited in organs, where they may cause harm.
BIG EYES
Short-sightednes
Beautiful as they may be, large eyes could mean you'll have to rely on glasses or contact lenses.
If your eye measures even 1mm longer than 24mm (the average size) you will be short-sighted.
Trevor Rowley, an optometrist from Viewpoint opticians in York, explains:
'If your eye is a normal length, the light will be clearly focused on the back of the eye.
'If it's a couple of millimetres longer than normal, the light will focus a couple of millimetres in front of the retina [where images are processed].'
SHORT LEGS
Diabetes
Long,coltish legs aren't just an asset on the catwalk, they can also indicate a lower risk of type 2 diabetes, research suggests.
A study at Bristol University showed that each 4.3cm increase of leg length resulted in a 19 per cent reduced risk of the disease.
'If your mother was relatively malnourished when you were in the womb, you may have smaller legs,' says Dr Mark Vanderpump, consultant endocrinologist at the Royal Free Hampstead NHS Trust in London.
'Once you've adapted to a low fuel state in the womb, your pancreas, which secretes insulin, may not be able to cope with a relatively normal amount of fat and carbohydrates after you're born.
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Hence the greater risk of lifestyle diseases such as type 2 diabetes in middle age.