THE AIR was clean, the fruit was fresh and not even the threat of a woolly mammoth attack could ruin a pleasant day of hunting and gathering.

Cavemen may have been on to something with their way of life, which could explain why their diet is making an unexpected comeback millions of years later.

But the Paleo Diet, which goes hand in hand with the CrossFit phenomenon sweeping the world, isn't for everyone, the Huffington Post reports.

The diet advocates eating the food that was around before the advent of modern farming. That means no grains, legumes, dairy, alcohol or sugar, but plenty of hand-reared meat, fresh produce and nuts.

It's praised by some for being the optimum human diet that lowers the risk of heart disease and helps with weight loss.

But critics question the logic of following the eating pattern. After all, cavemen only lived to the age of 25.

Cut through the hype and follow six principles that guide the Paleo Diet.

1. AVOID PROCESSED FOODS

This is Paleo orthodoxy but also common sense, which explains why it's recommended by just about every health practitioner and Harvard's School of Public Health.

Consuming whole foods, as close to nature as possible, is healthful.

2. PAIR DIET WITH EXERCISE

Paleo is the eating plan followed religiously by CrossFit acolytes. But even if the hardcore training method isn't for you, the idea that diet and exercise should be part of a healthy lifestyle is a good one.

Research shows that combining the two elements is the best way to lose weight.

3. ACHIEVE A GOOD SALT BALANCE

Processed foods are a major source of the sodium in the modern diet, so Paleo followers eat a low-salt diet without really thinking about their sodium intake.

Also, the Paleo plan provides nearly two times the amount of potassium that a typical diet includes.

That combination is a recipe for good vascular health and low blood pressure.

4. CHOOSE GOOD FATS

Poor old fat. It gets such a bad rap for having the same name as ... well ... being fat.

But there are good ones, which the Paleo Diet embraces.

Opt for single-source fats like avocados, olive oil, flaxseed oil and coconut oil.

Throw out hydrogenated vegetable oils.

5. COOK FOR YOURSELF

With strict eating guidelines, you're less likely to hit the vending machine for a quick snack or go to a restaurant for a weekend blowout.

That means most of the food you eat comes from your own kitchen. And that means you know exactly what's in it and how it will affect your body.

6. DON'T COUNT CALORIES

After all, cavemen certainly didn't.

Calories certainly count, and if you eat a lot of them, you'll gain weight. But they're not the metric of a healthy diet.

Calories are the starting point towards looking at the health value of food. The better measure of a food is how many nutrients it contains.

But perhaps the most important rule of the Paleo Diet isn't written in any of the literature.

7. PLEASE DON'T TALK ABOUT PALEO TO PEOPLE WHO DON'T CARE

Unless someone asks how you've shed so much weight or why you have steamed chicken and broccoli for lunch every day, keep it to yourself.

Thanks.

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