And one of them is positively prehistoric.

Back when people lived in caves, little did they realise they were paving the way for dieters of the 21st Century.

Eating like our ancestors is back in vogue and a growing tribe is following the Paleo or ‘Caveman Diet’, which on average has helped users shed on average 2.3 kilos in three weeks.

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Cooked meat is a staple, as are vegetables and fruit and nuts. There's no milk, no grains and definitely no processed foods.

He's no Neanderthal but 59-year-old Dennis Coleman has lost fifteen kilos since starting the caveman Diet last year.

“I've got more energy than I've ever had in my life. No headaches, no indigestion,” Coleman said.

A growing number of Paleo followers combine the diet with caveman training known as CrossFit.

“So when a caveman was hunting back in the day, he might need to sprint quickly or might need to have short bursts of activity,” personal trainer Nick Karp explained.

Karp has now developed Paleo Snacks made with almond meal and coconut.

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“There are so many people that work their nine to five jobs that come home feeling tired. If you fuel your body with the right foods your body will feel better for it,” he added.

However dietician Melanie McGrice says any diet plan that that cuts out entire food groups is a fad.

“I like the fact with the Paleo Diet that people are eating natural, healthy foods, but my concern is that they're cutting out core food groups,” McGrice said.

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“It doesn't really differ from other low carb diets, it is just another low carb diet, but even more concerning than some of the others in that it cuts out dairy products.”

Raising even more eyebrows than the Caveman is a diet called The OMG which targets teens and turns weight loss concepts on their head.

According to British actor, sports scientist and personal trainer Paul Khanna “you can expect to lose between ten and twenty pounds - and that's of fat.”

That’s about nine kilos in six weeks. The book ‘Six Weeks to OMG - Get Skinnier Than All Your Friends’ is the work of the 39-year-old who writes under the penname Venice A. Fulton.

“Everything in my book is research based. There are over 100 scientific studies, they're all studies performed beyond the year 2000,” he said.

Among the contentious claims is that it is good to skip breakfast, that certain fruits instantly block fat loss, that small, frequent meals are damaging, and that two cups of coffee a day and an icy cold bath will aid weight loss.

Despite being slammed by health experts, in many countries the book is sold out.

“It’s appealing to a certain type of person, the Gen Y, Facebook generation, using all that type of language they use,” Dr Samantha Thomas from Monash University said.

Dr Thomas is concerned the publishers are creating controversy to generate book sales.

“We see lots of promises but very little evidence associated with these new fad diets,” she said.

According to Oprah endorsed Dr Oz “it turns out there are a couple of basic differences between people who have their weight in their buttocks area v’s people who have it in their belly or arms and chest, and that boils down to your hormones.”

Dr Oz claims to be a wizard of weight loss and has a different diet for each type of problem area. Controversially his diet lasts just five days, but he hopes once followers see the results, they'll continue.

“It turns out that you will lose weight much more rapidly if you understand what diet would work for your body type,” Dr Oz said.

The Dukan Diet, The Atkins Diet, The Red Carpet Workout - there's practically a diet for every day of the year.

However the experts say to lose weight, just follow these tried and tested steps:

• forget the fads
• exercise for at least 30 minutes, three times a week
• say no to greasy food
• limit desserts and sweets
• stick to grilled, poached or roasted meats, with salads and vegies.

“Following fad diets is not a good idea at all. We know that they don't work out for most people in the long run. People should look at the evidence and start thinking about their lifestyle rather than always thinking about weight loss,” Dr Thomas concluded.

Contact details

• Paleo Snacks - www.paleosnacks.com.au
• Six Weeks to OMG - www.veniceafulton.com
• The Dr Oz Show - www.doctoroz.com
• CrossFit - www.crossfit.com

This reporter is on Twitter at @LyndaKinkade