A smoking habit can harm almost every part of the smoker's body. But doctors — and the smoking public — haven't always known that.
Before researchers laid bare the links between smoking and the many diseases it can cause, tobacco companies ran ads that promoted the health benefits of their cigarettes.
"Have you any of those little nervous habits such as twisting your handkerchief ... (or) playing with your ring?" asked one Call ad from 1934. "These may all be signs of jangled nerves. ... Remember, if you smoke Camels, you can smoke as many as you want, for Camel's costlier tobaccos never jangle your nerves."
This ad, of course, gets a lot wrong. Not only is smoking one of the unhealthiest possible habits; fidgeting — those "little nervous habits" — can actually be good for you.
History suggests, then, that it's not always easy to figure out which "vices" are worth ditching. So which "bad" habits are not actually bad for you?
'Bad' habits you can keep
Fidgeting. Studies suggest that people who make more "incidental" movements — such as repeatedly tapping their feet or getting up to walk to the restroom — have an easier time maintaining their weight and their heart and lung health. Fidgeting can also be a relatively healthy way to release nervous energy or creativity.
So if you fidget, there's no need to stop. That said, the benefits of fidgeting aren't great enough — and the results aren't conclusive enough — to justify dropping your exercise routine in favor of tapping your fingers on the table.
Double checking. Do you sometimes go back home a few minutes after leaving, just to make sure you locked the door? While they might make you late or annoy your spouse, these kinds of habits have a self-preserving effect. That one time the garage door really is open, or you really do have lettuce in your teeth, you'll probably be glad you checked.
That said, talk to your doctor if you compulsively check on things to an extent that significantly interferes with daily life, which can be a sign of a psychological disorder.
Drinking (in moderation). Drinking too much alcohol can increase your risk of alcoholism; head, neck, stomach and breast cancers; and risky behavior (which may, in turn, lead to car accidents or sexually transmitted infections).
But small quantities of alcohol can have health benefits, particularly for your heart. One large study found that moderate drinkers were about a third less likely than nondrinkers to have a heart attack.
The key is moderation. That means no more than one drink a day for a woman and no more than two drinks a day for a man. (One drink equals 12 ounces of beer, 5 ounces of wine or 1.5 ounces of liquor.)
A lot of times we don't think of bad habits as not doing things. But not exercising is actually one of the most common bad habits.
Habits you should break
Smoking. Even in the smallest quantities, smoking is bad for you. Try to quit as soon as you can. One trick is to set small goals and cut back gradually before quitting completely.
Think it'll take years for your body to reap the benefits of kicking the habit? Guess again: The benefits of quitting begin just 20 minutes after your last cigarette.
Not exercising. Not all bad habits are as obvious as smoking. A lot of times we don't think of bad habits as not doing things. But not exercising is actually one of the most common bad habits.
If you're too busy to go to the gym, you can still get the benefits of exercise by doing it in small chunks. Exercising 15 minutes in the morning, 15 minutes at lunch and 15 minutes after work are just as good as a continuous 45-minute workout.
Not sleeping enough. Another bad habit by omission, getting too little sleep can have serious health effects. Research has shown that chronic sleep deprivation increases your risk of high blood pressure, diabetes, obesity, depression, heart attack and stroke.
Most adults need seven to eight hours of sleep a night — so you should go to bed early enough to get that much. If you regularly have trouble falling asleep, discuss it with your doctor.
Looking at a screen right before bed. One way to get more sleep? Break the increasingly common bad habit of looking at a screen right before you go to bed.
It's believed that light, especially from things like TVs, tablets and smartphones, can affect the hormones that help us to sleep. So don't use these things within an hour or two of going to bed, especially if they you have problems with sleep.
Slouching. Screens also sometimes cause us to hunch over them. And routinely hunching or slouching, whatever the reason, can cause low back pain. If you spend all day sitting in front of a computer, stand up every so often (maybe even now) and walk around.