From your Lips to your Hips in Just 3 Hours

From digesting a cupcake to healing after surgery or even having an orgasm, how long it takes your body to work

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Some people will always be punctual, while others are perpetually late — and our bodies are no different. 

A recent study by the U.S. National Institute of Environmental Health Sciences found that ‘due dates’ are largely pointless, because the length of pregnancy can vary dramatically from woman to woman, with very few actually giving birth on their predicted day. 

So what about the other crucial processes in life — how long should they last? CHLOE LAMBERT and ROGER DOBSON asked the experts…

DIGESTION: 24 hoursThat sausage roll you’ve just scoffed will be in your stomach within three seconds of swallowing it, but the waste won’t be excreted until up to a day later.

Complex: High fat foods can hours for the stomach to break down

As soon as it reaches the stomach, it’s ground into tiny particles with the help of stomach acid, at a rate of about three to four calories a minute, says Dr Anton Emmanuel, consultant gastroenterologist at University College Hospital, London. 

‘A larger meal with a high fat content will be harder for the acid to break down, but a 600-calorie roast dinner, for instance, will be in your stomach for about two to three hours.’ 

Next, the food travels through the small intestine where it’s further broken down, and nutrients absorbed into the bloodstream, before entering the colon after another two to three hours, where water and salt are extracted. 

‘For the next 20-odd hours, it’s working its way through your colon so the whole thing takes about 24 hours,’ says Dr Emmanuel. 

‘But there’s a huge variation in what normal is — anything from 16 to 30 hours for a standard meal is considered healthy.’

Individual foods vary in time taken to pass through. A study from the University of Hawaii found it takes up to three days to digest a complex food such as a hamburger, whereas fruit can take less than an hour. 

Digestion is a bit slower in women than men — possibly because the gut hormones that aid digestion are less powerful in women, says Dr Emmanuel. 

Digestion also slows down with age as the system becomes less effective; drugs such as blood pressure medications and antidepressants can cause the bowel to slow right down.

Mood plays a part, too, he says. ‘Anxiety can slow digestion and that’s probably something that’s adapted — if you’re stressed you need more calories on board to cope with things.’ 

Certain conditions speed the process up — irritable bowel syndrome being the most common, causing the process to take less than 16 hours. 

Inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease, and an overactive thyroid, can have this effect, too (an underactive thyroid, however, slows  things down). This may be a factor in people with these conditions suffering a lack of vitamins and minerals and losing weight.

WOUND HEALING: Up to two yearsIt takes two years for the tissue to recover fully following a deep wound such as one sustained through surgery — although the actual healing process starts within seconds of the damage occurring, according to a study from Columbia University. 

In less than one second, the blood vessels leading to the wound tighten to reduce blood flow, and platelets are dispatched to help the blood clot and plug the opening.

Various substances, including the mineral calcium, vitamin K, and a protein called fibrinogen, form a type of net to hold the platelet plug in place, and a scab starts to form. 

With the wound sealed, about three weeks after the injury, scar tissue forms. Over the next two years or so, the scar tissue will become stronger, although it will look faded — it will eventually have about 80 per cent of the strength of the original skin. 

Various conditions can inhibit wounds healing, including diabetes, as can taking drugs such as corticosteroids, ibuprofen and aspirin, possibly because they weaken the net that holds the platelet plug in place. 

Vitamin C is vital for wound healing and so a lack of this could result in a cut taking longer to heal. 

Age and conditions that reduce the amount of oxygen in the blood, such as sleep apnoea, can also slow healing.

WEIGHT GAIN: Three hoursThis is the time it takes fat to reach the waistline after a big meal — dietary fat enters the blood around an hour after a meal, and after three hours, much of it is found in adipose tissue, the fatty tissue found mostly around the waist, according to research from Oxford University.

In a meal containing 30g of total fat (such as a chicken tikka masala or beef lasagne) there will be two to three teaspoons of fat in tissue around the waist after about three hours. 

That is temporary storage and will be used as an energy source — unless we eat too much, when it will remain, and accumulate, so we put on weight.

ORGASM: 20 mins for women, three for menAn orgasm can last anything from a few seconds to half a minute, studies show — however, the time it takes to reach that point varies: for women, an average of ten to 20 minutes; for men, two to three minutes.

But Professor John Studd, a gynaecologist from the London PMS and Menopause Clinic, questions the findings, saying there are too many variables to give an average length of time.

‘Orgasms — and libido — are a mixture of head, heart and hormones.  There are no hard and fast rules.’

REPLACE A PINT OF BLOOD: Up to six weeks

After losing or donating a pint of blood, it takes around 24 hours for the watery part of the blood, the plasma, to be replaced. 

But it takes the red blood cells —which carry oxygen — much longer, about four to six weeks. The process starts with cells in the kidneys — the peritubular cells — sensing the oxygen level in the blood has dropped.

In a meal containing 30g of total fat (such as a chicken tikka masala or beef lasagne) there will be two to three teaspoons of fat in tissue around the waist after about three hours. 

That is temporary storage and will be used as an energy source — unless we eat too much, when it will remain, and accumulate, so we put on weight.

ORGASM: 20 mins for women, three for menAn orgasm can last anything from a few seconds to half a minute, studies show — however, the time it takes to reach that point varies: for women, an average of ten to 20 minutes; for men, two to three minutes.

But Professor John Studd, a gynaecologist from the London PMS and Menopause Clinic, questions the findings, saying there are too many variables to give an average length of time.

‘Orgasms — and libido — are a mixture of head, heart and hormones.  There are no hard and fast rules.’

REPLACE A PINT OF BLOOD: Up to six weeks

After losing or donating a pint of blood, it takes around 24 hours for the watery part of the blood, the plasma, to be replaced. 

But it takes the red blood cells —which carry oxygen — much longer, about four to six weeks. The process starts with cells in the kidneys — the peritubular cells — sensing the oxygen level in the blood has dropped.

They start secreting erythropoietin, a protein that travels to the bone marrow to trigger the production of stem cells, the building blocks needed to make blood cells. 

Men who donate blood have to wait a minimum of 12 weeks before doing it again; women, 16 weeks. This is because men normally have more iron stores, needed to produce red blood cells.

CONCEPTION:  30 minutesIt takes as little as half an hour for a sperm to travel up the cervix and fertilise an egg in the fallopian tubes. 

The egg releases a hormone that attracts the sperm, which reacts in under a second, according to research from the University of California. Fertility problems can occur if the egg doesn’t release enough of the hormone, or if the sperm cells don’t recognise it. 

Once an egg is fertilised, gestation time can vary massively, as researchers at the U.S. National Institute of Environmental Health Sciences have found — anything from 37 to 42 weeks. 

The researchers found older mothers, and women who had themselves been heavier at birth, were more likely to have longer pregnancies, though it’s not clear why.

Delivery of a baby is triggered when the foetal lungs fully develop — this sends a signal to the uterus to start contracting. However, several factors can affect the timing, says Dr Victoria Beckett, of the Royal College of Obstetricians and Gynaecologists.

‘If the womb is very big — for example, if a woman is having twins — or in diabetic pregnancies, or if there’s infection around the womb, the signal can go off early.’

Although babies born between 37 to 42 weeks are normally healthy, a study published last year in the British Medical Journal found those born at 37 to 38 weeks are more likely to have health problems such as asthma and gastrointestinal disorders. 

Meanwhile, those born after 42 weeks (who are usually induced) are more at risk of behavioural disorders such as Attention Deficit Hyperactivity Disorder (ADHD), according to Dutch research, perhaps because these babies are often bigger, so the placenta can’t provide enough oxygen and nutrients.

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