Want to lose weight? Act like a caveman and following the Paleo lifestyle, which is a diet and exercise regimen based on the caveman days. The trend has been around for decades but it recently started taking off again. Experts say over a million North Americans follow it, including actress Megan Fox. So, what’s on the caveman diet menu? It’s anything that our ancestors ate in 10,000 B.C., like grass-fed meat, vegetables, fruit, and nuts. What’s not on the menu: Dairy and grains, because farming wasn’t invented yet, and absolutely no Cheetos. In fact, all processed food is out. Fans are so hooked on the diet there’s even a bestselling Paleo diet cook book, with recipes for everything from wild salmon basil burgers to grilled chicken kebabs.

Right now, the trend’s so hot that gyms offering Paleo-workouts are popping up everywhere. However, there’s not a single elliptical machine or treadmill in sight. Instead, Paleo gyms are packed with equipment that gives you a full-body work out from the Paleo days, like sprinting away from predators and climbing trees. For present-day equipment, that translates to gymnastic rings, pommel horses, and cargo nets for climbing. One man we read about says that Paleo exercises have given him the strength to pull his Range Rover with his bare hands. Fellow Paleo exercisers aren’t mindlessly listening to their iPod while walking on a treadmill. Instead, they’re encouraging and working alongside each other.

So, does the Paleo lifestyle really work? Nutritionists all say yes, because it balances meat and vegetables which your body needs to thrive. You may still want to update your Paleo diet by a few eras by adding heart-healthy whole grains and dairy to keep your bones strong. If you want to go further, check out the website ThePaleoDiet.com.