In order to stay healthy and slim, Professor Spector says the best thing you can do is eat food that promotes the reproduction and growth of good bacteria in the gut — like chocolate, within moderation. Joel Ryan / PA Archive/Press Association Images It might seem like the last thing you should do, but now anyone trying to lose weight should consider eating more chocolate and cheese and drinking more wine.

The British dieting industry is worth £2 billion with recent research showing that 48 per cent of us having tried to lose weight in the past year.

And it doesn't seem to be working, with studies showing the British population is three times more overweight than it was in 1980.

Now, a scientist at King's College London has said that the lack of success in losing weight is due to our ignoring one key factor: the microbes in the gut.

Tim Spector, professor of Genetic Epidemiology and author of "The Diet Myth: The Real Science Behind What We Eat," says that there are around 4lbs of microbes in the average gut, and that the microbes in the body outnumber our own cells by 10 to one.

And what should really be on the menu for someone who wants to lose weight? Professor Spector recommends chocolate, wine, coffee and cheese.

Speaking at the Oxford Literary Festival, he argued every individual has a different set of microbes in their gut, which can influence processes in our bodies – including how much we weigh.

Fad diets, most of which involve either pedantic calorie control or the complete elimination of one or more food groups, fail to help most people shed unwanted weight in the long term. Professor Spector claims that this is because they disregard the vital role that gut microbes play.

Calorie control on its own is unlikely to work, says Professor Spector, because studies show that calories from one type of food will have a completely different effect on weight than calories from another.

Professor Spector cites a six-year study on monkeys, some of whom were fed calories from healthy vegetable oil while others had calories from artificial trans. Both groups consumed the same number of energy, but that latter gained weight and the former did not.

In "The Diet Myth," Professor Spector says: "Our narrow, blinkered view of nutrition and weight as a simple energy-in and energy-out phenomenon and our failure to account for our microbes have been the main reasons for the miserable failure of diets and nutritional advice."

Other diets involve the practice of "cutting out" a food group, whether it be carbohydrates, fats or everything other than cabbage soup. Professor Spector claims that these sorts of diets could actually contribute to weight gain or ill-health, because lack of dietary diversity decreases the diversity of microbes in the gut.

"The increasing promotion and use of restrictive diets that depend on just a few ingredients," says Professor Spector, "will inevitably lead to further reduction in microbe diversity and eventually to ill-health."

In order to stay healthy and slim, Professor Spector says the best thing you can do is eat food that promotes the reproduction and growth of good bacteria in the gut.

He claims that people with more diverse gut microbes are slimmer and healthier, according to years of studies he conducted on twins.

The good news is that Dr Spector says chocolate, wine and coffee are definitely on the menu for a person looking to increase the diversity in their gut.

All three of these contain polyphenols: anti-oxidants which feed the microbes in the gut and allow them to reproduce.

Wine and chocolate contain a type of polyphenols called flavonoids, which Professor Spector claims have "anti-inflammatory, anti-oxidant and important microbial effects."

Flavanoids can also be found in olives and nuts, but "gram for gram, cocoa has the highest concetration of polyphenols and flavonoids of any food."

In a study of 2,000 UK twins, Professor Spector and his colleagues found that twins with the highest levels of blood-flavonoids from wine and chocolate had "lower weights, better arteries, ower blood pressure, stronger bones and a lower risk of diabetes."

It's worth remembering, though, that it's the cocoa in chocolate that has been shown to be good for your gut, not the milk and sugar that comercial chocolate is filled with.

Cheese is also a good choice, unpasteurised cheeses. Cheeses contain "a wide variety of microbes including bacteria, yeasts and fungi, and hundreds of species plus thousands of known and unknown strains."

All of these things help contribute to diversity of microbes in the gut, which he claims could make you lose weight and live longer, as well as reducing risk of diseases.

Unfortunately, having a glass of wine, a chunk of camembert and an entire family-sized bar of chocolate for dinner every night is not the way to go.

The best way to increase the diversity of gut microbes is to increase the diversity in the diet. The reason why diets heavy in "junk" tend to lead to weight gain is not necessarily because of fat and sugar content, but because heavily process food has very few ingredients.

Eating a wide range of foods and keeping up a varied diet, including rich in polyphenols and healthy bacteria.