A recent study showed how eating junk food can lead to an imbalance in the healthy bacteria that helps keep people thin. Tim Spector, a professor at King’s College London and specializes in genetic epidemiology, explains how the rising obesity levels are partially related to the increase in processed foods in the diets of many people. Those who opt for a diet that helps healthy bacteria flourish may have just as much success with weight loss as those who focus on reducing fat and sugar intake.

Spector identifies several foods that can help healthy bacteria grow, including celery, garlic, unpasteurized cheese, dark chocolate, and even Belgian styles of beer.

Estimates from the World Health Organization suggest that about 2/3 of women and 75% of men in the UK will be overweight by 2030.

Spector estimates that the amount of healthy bacteria in the average person’s gut has decreased over the past 50 years because of the increase in consumption of processed foods. He conducted an unusual experiment, using his 23-year old son as an example. Spector’s son, Tom, consumed only McDonald’s burgers, chicken nuggets, chips, and soda for a ten-day period. Researchers obtained samples of bacteria from Tom’s gut before and after the experiment for comparison.

At the initiation of the experiment, 3,500 different species of bacteria were found in Tom’s gut, while at the end of the 10-day period, only 2,200 species were found. This is a reduction of 1,300 species in only 10 days. Not only did Tom manage to kill off over a thousand species of healthy bacteria, he gained four pounds during the 10-day period.

Spector comments, “Microbes get a bad press, but only a few of the millions of species are harmful and many are crucial to our health. Microbes (bacteria) are not only essential to how we digest food; they control the calories we absorb and provide vital enzymes and vitamins. It is clear that the more diverse your diet, the more diverse your microbes and the better your health at any age.”

Spector emphasizes that a diet intended to increase the range of bacterial species in the gut is just as critical to maintaining a healthy weight as reducing fat and sugar intake. He indicated that 15,000 years ago, human ancestors consumed about 150 different ingredients per week, which helped healthy bacteria to proliferate in the gut. Today, most people consume fewer than 20 different types of food, and this number drops as the amount of processed foods consumed increases. This is because processed foods are made from four main ingredients: corn, soy, wheat, and meat.

As restrictive diets are more heavily promoted, there may be an even greater decrease in the microbe diversity required for a healthy gut, leading to more health problems.

Spector is close to publishing his book, The Diet Myth, which explains the processes related to developing healthy gut bacteria, and offers guidelines regarding the best foods to eat to promote healthy bacterial growth.