Ever wondered why you're not getting any thinner after those 3 Big Macs? According to new research, eating junk food kills the stomach bacteria responsible for preventing obesity, cancer, heart disease, diabetes, inflammatory bowel conditions and autism.

I didn't even know there was so much good bacteria in there. The new study revealed in a press release, was conducted by Tim Spector of King's College in London.

Spector, a professor of genetic epidemiology enlisted his 23-year-old son, Tom in the experiment.

Tom consumed a diet of McDonald's hamburgers, fries, chicken nuggets and coke. According to The Australian:

Before I started my father’s fast food diet there were about 3,500 bacterial species in my gut, dominated by a type called firmicutes. Once on the diet I rapidly lost 1,300 species and my gut was dominated by a group called bacteriodetes. The implication is that the McDonalds diet killed 1,300 of my gut species.

Spector's research reveals that having a diverse range of bacteria living in your stomach is what keeps us thin and healthy.

Microbes get a bad press, but only a few of the millions of species are harmful and many are crucial to our health […] Microbes 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 believes the key to preventing obesity and staying healthy is to have a diet that increases the range of bacteria in your stomach.

Spector has an upcoming book too titled, "The Diet Myth: The Real Science Behind What We Eat."