This article is part of a series about the past, present, and future of commuting in America.

Many Americans are obsessed with rooting out things that make us unhealthy — even to the point of overkill. We detox, we avoid gluten, we devise excessively complicated exercise regimes (even though these are all unnecessary).

And yet for some reason, we seem to have no problem doing a simple activity every single weekday that's associated with obesity, high blood pressure, sleeplessness, and general unhappiness.

That activity is commuting — or at least commuting alone by car.

About 85 percent of Americans get to work by car, spending an average of 50 minutes round-trip sitting on their butts. Given everything we've recently learned about the health problems linked to sitting all day at work, it might not be a huge surprise that a long, sedentary commute is also associated with several different health problems, including obesity.

Related The utter dominance of the car in American commuting

But what might be a surprise is how dramatically a long commute affects people's self-reported rates of well-being, stress, and overall satisfaction with life — if you do it alone.

Spending more than two hours of your day commuting — as 8.3 percent of American workers now do — will probably make you miserable. But there's research that suggests doing it with other people will make it far less unbearable.

How long commutes lead to obesity

The association between long drives to work and poor health has turned up in a number of different studies (see this Slate article by Annie Lowrey for one excellent overview).

"We've found that people who commute longer distances are less fit, more likely to be obese, and have worse metabolic outcomes than those with shorter ones," says Christine Hoehner, a doctor at Barnes Jewish Hospital in St. Louis.

Hoehner conducted a study of 4,297 Texas workers and found that those with long commutes (greater than 20 miles) had greater rates of high blood pressure and high blood sugar than those with short commutes (0 to 5 miles).

But when researchers probed further, they found that it wasn't commuting itself that was making people fat. Instead, it was the fact that commuters were less likely to get exercise. When the researchers corrected for this variable, the effects mostly disappeared.

Most people seem to lose their willpower to exercise after sitting in traffic

On the surface, this might sound like good news. In theory, the negative effects of commuting can be counteracted — as long as you exercise at home.

Unfortunately, the sad truth is that most people seem to lose their willpower to exercise after sitting in traffic for long stretches of time. Economist Thomas James Christian analyzed data from the American Time Use Survey and found that people who spent more time commuting consistently spent less time exercising, sleeping, and making food at home. They were also more likely to buy "non-grocery food purchases" (i.e., fast food or takeout).

Interestingly, long commutes are more likely to cut into these "health-promoting behaviors" than long workdays alone. It seems there's something specific about a long commute tacked on to the end of a workday that drains us of the willpower to exercise or eat right.

What's more, even if you do exercise, there's still evidence that commuting can be bad for your health in other ways. Hoehner found that people with long commutes tended to have higher blood pressure — even after controlling for exercise. And a Gallup poll of 173,581 US workers, meanwhile, found that those who commute more than one hour each way are more likely to have chronic back or neck pain.

Long commutes also make us miserable

Even setting aside obesity and blood pressure, commuting makes us unhappy in all sorts of other ways.

"Commuting clearly makes us stressed," says British transportation researcher Daniel Newman, pointing to several studies — including a study of 21,000 workers in Sweden — that have found an association between longer commutes and higher levels of chronic stress. (This might explain why commuting leads to higher blood pressure, though that's not certain, since we still don't have hard evidence that chronic stress actually causes hypertension.)

One reason commutes are so stressful, economists say, is the unpredictability and lack of control. Not only are you spending lots of time in your car, but you're also facing stress when you hit a traffic jam and worry that you'll be late for work or to pick up your kid.

People with long commutes report being more exhausted and rate their overall well-being lower on a daily basis

Commuting also seems to be terrible for our sleep. Both the Swedish study and a study of commuters on the Long Island Rail Road found that people with long commutes sleep less, while the Swedish study also found that they report being more exhausted and rate their overall well-being lower on a daily basis.

It gets worse. The Gallup poll also found that those with longer commutes report spending more time worrying, feeling less well-rested, and experiencing less enjoyment in life in general. Finally, in a recent British government study, workers with commutes longer than an hour reported feeling more anxious, less happy, and less satisfied with life, and were less likely to state that their daily activities were worthwhile as a whole.

How to save yourself from a terrible commute

When it comes to physical health, there's good reason to believe that walking, biking, or even taking public transit is healthier in the long term than driving.

Related Biking or walking to work will make you happier and healthier

A recent British study, for instance, found that commuters who take any form of transportation besides driving solo had 1 to 2 percent less body fat, on average — and a lower chance of being obese — even when (non-commuting) exercise, age, and other health factors were taken into account. That this held true for people who took the train or bus suggests that simply having to walk to a station or stop at either end of your commute, every single day, can make a difference in the long term.

Research shows that people underrate the cost of a long commute and overrate the benefits

Of course, in the United States, car-free commuting isn't really an option for the vast majority of people. Many cities don't have the public transportation infrastructure to make other options viable. Many people's residences and places of work simply dictate that they have to drive.

But even if that's the case for you, you can choose to live closer to your place of work. Research shows that in terms of their long-term happiness, lots of people underrate the cost of a long commute (all the time they sacrifice to it) and overrate the benefits (a larger house or nicer neighborhood). Some economists calculate that you'd need a 40 percent salary bump to justify an extra hour of commuting time daily.

And regardless of where you live, there's a surprising thing you might do to make your car commute less miserable: carpool.

Carpooling has declined precipitously in the US since 1970. Which is too bad, because there's some evidence that it's a much more enjoyable form of commuting.

In 2006, the economists Daniel Kahneman and Alan Krueger looked at how much time people spent doing a variety of daily activities, and how stressed, happy, sad, and worried they felt while they were doing them. Overall, commuting ranked right near the bottom, lower than housework and child care, and right down there with working.

Interestingly, though, when people's commutes involved any sort of social contact — whether carpooling or chatting on the train — it shot up to the middle of the rankings, with ratings similar to napping, watching TV, or talking on the phone.

This surprising finding points at what some experts believe is the deeper psychological problem with a longer commute. "The longer you spend commuting, the less time you have to socialize and make friends, or spend with loved ones," Newman says.

The biggest problem with a long driving commute isn't necessarily that you're sitting down, or stressed out in traffic. As Nick Paumgarten put it in an excellent 2007 New Yorker article on commuting: