Perhaps you've heard of the paleo movement – eating and exercising as our ancient forefathers did – and dismissed it as a fad, a farce, a caveman version of the Atkins diet. But over the past few years, the philosophy has exploded from obscure scientific theory into one of the biggest trends in wellness, influencing everything from medicine to running shoes to the latest thinking on how we should eat and move to stay lean and healthy.

Many experts now believe that Western civilization's skyrocketing rates of degenerative disease – diabetes, heart disease, cancer, and Alzheimer's, to name a few – stem from our adoption of a diet high in processed foods, exacerbated by our sedentary lifestyles. In 1985, a pair of researchers published a provocative paper leveraging the fact that, while the human species has existed for about 2 million years, grain production is only 12,000 years old, and the rise of processed foods – new to humans on an evolutionary scale – mirrors our uptick of weight gain and chronic disease. Cavemen didn't suffer from most of these diseases, primarily because their diet consisted mostly of meat, vegetables, and some fruit. They rarely died of heart attack or stroke, but from old age, viruses, or calamity like extreme weather. Today, those who still eat a traditional diet, like the Arctic Inuit and Kenyan Maasai, are virtually immune to these diseases too.

After 1985, the paleo movement started collecting members slowly but steadily, until it exploded about two years ago, launching a bevy of self-help books, snack foods like jerky and coconut chips, and the Paleo Physicians Network, with more than 2,000 members and a mission to educate doctors about treating patients based on our evolutionary nature. Crossfit, the minimalist fitness craze, has adopted paleo as its unofficial nutrition mantra – no carbs, lots of meat and vegetables. "It's about getting complete and total control over your health," says Mark Sisson, author of 'The Primal Blueprint.' "It's about having more energy at 50 than you did at 35. It's so empowering that followers become the biggest proselytizers. Everybody wants to know how they lost their 70 pounds."

More profoundly, the human genome has remained relatively stable since our hunter-gatherer days, while our diets have changed drastically. We now eat massive amounts of sugar, which triggers our bodies to store fat. Most processed foods are made from sugar, grains, and industrial vegetable oils high in trans fats, which the National Academy of Sciences declared unsafe in food in any amount. Most of what we eat is grown with pesticides, linked to cancer, birth defects, and brain disorders, and treated with carcinogenic preservatives.

As we subsist on more sugar, grains, and chemicals, we move less and spend more time hunched over steering wheels, computer screens, and smartphones. Those who exercise often jump on a treadmill or weight machine, training their bodies and isolating muscles in unnatural ways. Few of us have the muscle mass, lung capacity, or reaction time to sprint up uneven hills, duck branches, hop boulders, and pull ourselves up a ledge to avoid a bear. But that's how the paleo crowd thinks we should move.

Of course, paleo has its detractors. 'US News and World Report' cited it as the worst of 24 popular diets, based largely on the notion that "duplicating such a regimen in modern times would be difficult." They also noted that the benefits of the paleo diet are largely unstudied, a point the paleo community contends. But last summer, a study funded by the National Institutes of Health helped mute the debate when it found a paleo-style diet, high in fat and low in carbs, to be the most effective for weight loss.

If you're health conscious, there's a good chance you've already adopted some of the paleo approach. For example, paleo followers have long supported barefoot running as a way to strengthen muscles in the feet. High-intensity training, TRX suspension straps, and extreme races like Tough Mudder and Spartan Race are all paleo-approved. And limiting carbs to load up on grass-fed meat and organic produce is key to living primal. Ready to go full steam? Here are five steps to adopt the paleo approach:

Eat Like a Caveman
One of the most prominent voices in the paleo movement is journalist and author Gary Taubes, who argues that it's not calories alone that cause weight gain, but sugar and refined carbs, which spike our blood sugar and trigger the hormone insulin, telling our bodies to store energy as fat. When we eat cereal for breakfast, sandwiches for lunch, and pasta for dinner – supplemented by soda, chips, and fries – these processed foods cause larger waistlines and diabetes, heart disease, and possibly even cancer over time. While medical experts used to think eating fat made people fat, "it has been clear for some time, from multiple trials, that the percent of calories from fat in the diet has minimal relation to weight gain or obesity," says Dr. Walter Willett, of the Harvard School of Public Health. Instead, says Willett, low-fat, high-carb foods, once believed to aid heart health and weight loss, are the real problem. Eating more healthy fat and fewer foods that spike insulin is the first step to primal eating. Second is to avoid industrial oils like soy and corn, rich in trans fat and inflammation-causing omega-6s. When you eliminate sugar, refined carbs, and industrial oils, you essentially eliminate all fast and convenience foods.

Move Like a Hunter
Movement in the Paleolithic era was never prescribed: The body adapted to challenges at hand, whether running from a predator, hauling a carcass, or building a shelter. We were always on the go, often at maximum output for short times. "Our caveman ancestor wouldn't have run every day because that's stupid," says Sisson, a former marathoner. Another proponent of paleo fitness is Erwan Le Corre, a 41-year-old Frenchman who founded MovNat, fitness that focuses on natural human movement. You can see him on YouTube running barefoot through the desert, rolling through brush, hurtling over rock ledges, and swimming downstream while pushing a 500-pound log. Le Corre calls this the workout the world forgot. "Modern lives are so separated from nature and what is natural that a system like MovNat is not only refreshing, it's also powerfully effective at connecting people with their bodies," he says. MovNat has thousands of followers, including members of the Special Forces.

Avoid Daily Toxins
There are toxins everywhere in our daily environment, and some of them, like pollutants in the air, can't be avoided. But others can. Since tap water can be contaminated with pollutants like arsenic and pharmaceuticals, read your local water reports and filter if necessary, and try to avoid drinking water out of plastic bottles. Eat organic foods when possible, buy food in bulk or glass, and use natural cleaners, detergents, and skin products.

Limit Modern Stressors
Our ancient ancestors had plenty of stress, whether hunting for food or keeping warm and dry in inclement weather, but it may not compare with the stress we've created in modern-day life. One of the biggest forms of modern stress? Sitting for most of the day, which takes a toll on our muscular and cardiovascular health. Fight it by using a stand-up desk or taking a walk every hour. Forgo the drudgery of soulless cardio equipment with TVs and muscle-isolating Cybex machines for activities that reinforce pleasure, whether it's forcing your body to move in unexpected ways by playing tennis or helping your muscles adapt to uneven surfaces by hiking. Choose outdoor exercise to get sun and vitamin D, which increases levels of relaxing serotonin. Never underestimate the power of play – but know it's also important to prioritize sleep over staying up late to work on your iPad or surf the Web.

Adopt a Primal Attitude
Primal living is more than a diet or new way of working out – it's a lifestyle. Once you eat and move in a way that's optimal for your body's design, you never go back. And there's a mind-set that goes along with that. Sisson believes it's important to get out of your comfort zone and try new things, whether that's building a tree house for your kids or learning to surf. Filter out negative, sensationalized news, and nurture small social networks rather than trying to collect 1,000 friends on Facebook. Most important, learn to unplug and recharge in the digital age of evolution.

See also:
Seven Rules for Eating Paleo
Five Primal Workouts to Reboot Your Fitness