You know the signs you're unhealthy, right?
You can't get off the sofa without breaking into a sweat. You're never more than a week from your next bout of the sniffles. You have the greyish look of the permanently unwell.
But how do you know if, actually, you're a pretty healthy guy? Apart from not feeling ill, the signs of good health are usually more vague and subtle than the signs of sickness.
Being healthy doesn't necessarily mean leaping out of bed every morning with an irritating swagger, or never getting a cold, or being able to run ultra-marathons after two weeks of training. You can be healthy without feeling you've always got energy to burn.
So how do you really know that you're doing OK? Luckily, there are some clues. They are not definitive, but taken together and in the absence of symptoms of illness they do suggest a body in pretty good working order.
Here are a few of them.
To test your fitness, you don't have to run for miles or do 200 push-ups. Experts say that the average person should be able to walk a mile in 15 minutes, carry two bags of shopping to the car, and climb the stairs in a house without getting breathless.
But that doesn't take into account age or gender. More specifically, a 30-year-old man with above average strength and fitness should be able to do over 25 push-ups in a minute and over 35 squats.
As long as you have a watch and the ability to count, you can measure a couple of your vital signs from the comfort of your armchair. A resting pulse of around 70 beats per minute and a respiratory rate of around 16-20 breaths per minute don't make you an athlete, but they do make you a normal, healthy adult.
Men don't pay much attention to their fingernails, but they can give vital clues to general health. Yellow nails are suggestive of respiratory disease, spoon-like nails curving outwards can mean iron deficiency anaemia, and lines going across the nails may be a symptom of diabetes.
Go to the doctor if there's any major change in the look or feel of your fingernails. Firm, pink nails, on the other hand, can be evidence of a decent general level of health.
If you're about to have lunch, it might be wise to skip this bit till you've finished. In a word, we're talking stools, because stools can speak volumes about overall health.
It's not so much how often you pass them that's important (unless this suddenly changes) once a day, three times a day, or even every other day can all be healthy depending on the individual but consistency and colour.
A good stool is torpedo shaped, soft and easy to pass. Colour can depend on what you've eaten, but it shouldn't generally be grey, very pale, too dark or bright red. A mid-brown stool, passed easily and regularly without any sudden change in bowel habits is one sign of decent digestive health.
And to continue the theme, if you have pale yellow pee you're drinking enough fluids and in the absence of other symptoms probably don't have any urinary tract infections.
A good colour is also a sign that your liver is working efficiently. Don't worry if you drink a lot of water and you're urine turns almost clear apart from the inconvenience of all those trips to the toilet, that's no problem.
A darker yellow probably just means you've been drinking less drink more to avoid the symptoms of dehydration. But dark or red-tinged urine or pee with a sweet or strange odour can be a symptom of health problems.
Shiny, healthy hair
A fine and luscious head of shiny hair not only looks good, it's also a sign that good things are happening in your body.
In particular, healthy hair can be a sign of a healthy diet. Dull, dry and brittle hair can be caused by a lack or protein, vitamin E or essential fatty acids. Hair so healthy women want to run their fingers through it may be evidence that you're absorbing plenty of body-friendly nutrients.
Doctors can tell a lot from your tongue. A tongue with a warm, pinkish colour is one clue that you are absorbing sufficient iron, folic acid and vitamin B12. An overly pale and smooth tongue can be a sign of anaemia, while a yellowish tint can suggest fungal infection.
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