Ditching restrictive dieting and calorie-counting is the key to maintaining a healthy weight according to a leading scientist determined to change how we eat.

Instead, the secret to health is nurturing the microbes in our guts, according to Professor Tim Spector, a geneticist at King's College London.

Professor Spector told The Independent that counting sugar, fat and calories is the wrong way to approach food. “Eat as much as you want, just think of your microbes,” he says.

“We have about 100 trillion microbes inside our body in the lower intestine or colon and a microbe is anything you need a microscope to see. We generally talk about bacteria, but there are viruses and fungi too and they all contribute to our health."

Microbes help to digest food, are crucial to the immune system, and provide about a third of the body's vitamins and chemicals. The food a person eats affects the health of their microbiome, with emerging research suggesting it can change our body's responseto medication, too.

"We are all unique in our microbes, which explains why we respond differently to foods," explains Professor Spector.

There are three rules that everyone can following, Professor Spector says, to promote a diverse microbiome: eat real food that is not processed, increase fibre intake, and have a diverse diet.

“You don’t have to cut anything out of your diet. I’m against excluding real food," he stresses.

The average person can, therefore, eat dairy, small amounts of meat, and carbohydrates. The best diet is one that is varied, and doesn’t include the same foods every day.

The world's biggest food fights Show all 11 1 /11 The world's biggest food fights The world's biggest food fights La Tomatina, Buñol, Spain Revellers throw tomato pulp at each other during the annual "tomatina" festivities in the village of Bunol, near Valencia on August 26, 2015. Some 22,000 revellers hurled 150 tonnes of squashed tomatoes at each other drenching the streets in red in a gigantic Spanish food fight marking the 70th annual "Tomatina" battle. AFP PHOTO / BIEL ALINO (Photo credit should read BIEL ALINO/AFP/Getty Images) Biel Alino/AFP/Getty Images The world's biggest food fights La Tomatina, Buñol, Spain A reveller is pelted with tomato pulp during the annual "tomatina" festivities in the village of Bunol, near Valencia on August 31, 2016. Today at the annual Tomatina fiesta 160 tonnes of ripe tomatoes were offloaded from trucks into a crowd of 22,000 half-naked revellers who packed the streets of Bunol for an hour-long battle. / AFP / BIEL ALINO (Photo credit should read BIEL ALINO/AFP/Getty Images) Biel Alino/AFP/Getty Images The world's biggest food fights La Tomatina, Buñol, Spain Revellers covered in tomato pulp participate in the annual "tomatina" festivities in the village of Bunol, near Valencia on August 31, 2016. Today at the annual Tomatina fiesta 160 tonnes of ripe tomatoes were offloaded from trucks into a crowd of 22,000 half-naked revellers who packed the streets of Bunol for an hour-long battle. / AFP / BIEL ALINO (Photo credit should read BIEL ALINO/AFP/Getty Images) Biel Alino/AFP/Getty Images The world's biggest food fights World Custard Pie Championship, Kent Funk Dooby/Flickr The world's biggest food fights World Custard Pie Championship, Kent Funk Dooby/Flickr The world's biggest food fights La Merengada, Vilanova i la Geltrú, Spain Ajuntament de Vilanova i la Geltrú The world's biggest food fights La Merengada, Vilanova i la Geltrú, Spain Ajuntament de Vilanova i la Geltrú The world's biggest food fights Battle of the Oranges, Ivrea, Italy Giuseppe Cacace/AFP/Getty Images The world's biggest food fights Battle of the Oranges, Ivrea, Italy Giuseppe Cacace/AFP/Getty Images The world's biggest food fights Clean Monday, Galaxidi, Greece Louisa Gouliamaki/AFP/Getty Images The world's biggest food fights Clean Monday, Galaxidi, Greece Louisa Gouliamaki/AFP/Getty Images

Fermented foods, including plain natural yogurt without any sugars or sweeteners, as well as keffir, un-pasturised cheese, miso soup, kimchi and sauerkraut (both created naturally as opposed to in vinegar) and tempeh boost the gut microbiome.

Rather than five a day, Professor Spector suggests eating seven portions of fruit and vegetables a day, including herbs and raw seeds. Skipping meals, as seen in the 5:2 diet, can help microbes “tidy up the gut” and make it more efficient.

Professor Spector himself admits it was tough to change his own diet to a gut-friendly one. Now, he eats yogurt sprinkled with seeds and berries for breakfast, a shot of black coffee, and a glass of keffir. For lunch he opts for nuts and fruit, and a vegetarian meal for dinner which could include a Thai curry, vegetable paella, lentil burgers, or salads with cheese. He eats meat only twice a month to reap the benefits of vitamin B12 present in animal products.

Antioxidant polyphenols, which are present in olive oil, are also important says Professor Spector, who published The Diet Myth last year.

Currently, experts can use tests to measure the diversity of a person’s gut and tell if it is abnormal.

In five years, Professor Spector predicts that GPs will use such tools to help patients better understand their gut health, as they do now to measure blood pressure or bone density. This could prevent people from self-diagnosing intolerances, which has caused the rise of gluten-free food among those who aren’t celiacs.