The diet of the children of Burkina Faso in the 'dark continent' could be far more sensible than what the western kids are reared on.
Restore the ancient balance in diet to keep humans leaner and healthier, researchers urge.
The findings, published in the Proceedings of the National Academy of Sciences, may support the development of probiotic products.
"Our results suggest that diet has a dominant role over other possible variables such as ethnicity, sanitation, hygiene, geography, and climate, in shaping the gut microbiota," says Paolo Lionetti of the University of Florence in Italy and colleagues write.
"We can hypothesise that the reduction in richness we observe in EU compared with Burkina Faso children, could indicate how the consumption of sugar, animal fat, and calorie-dense foods in industrialised countries is rapidly limiting the adaptive potential of the microbiota."
The study builds on a body of evidence that human health relies heavily on the trillions of microorganisms living in and on our bodies. Only a fraction cause disease directly - many more help digest food, affect other bacteria and may influence hundreds of biological functions.
Several recent studies have found that certain bacteria cause inflammation that can affect appetite as well as inflammatory bowel conditions like Crohn's disease and colitis, including a study published in Science in March.
"Western developed countries successfully controlled infectious diseases during the second half of the last century, by improving sanitation and using antibiotics and vaccines," the researchers write.
"At the same time, a rise in new diseases such as allergic, autoimmune disorders, and inflammatory bowel disease both in adults and in children has been observed," they add.
Lionetti's team studied the DNA of the gut bacteria of children in Burkina Faso, who are breast-fed up to age two and eat a diet rich in whole grains such as millet, legumes such as black-eyed peas, and vegetables. They eat very little meat.
The Western diet, in contrast, is heavy in meat, processed grains, sugar and fat.
The Italian team found the African children had many bacteria that help break down fibre, but the European children were lacking these microbes. The ratios were similar to studies comparing the gut bacteria of lean people to obese people.
This bacterial balance could even be causing obesity, the researchers say. It may also be useful to test children for these bacteria to see if they are at high risk of becoming obese, they add.
"Reduction in microbial richness is possibly one of the undesirable effects of globalization and of eating generic, nutrient-rich, uncontaminated foods."