The trendy "paleo" diet — a plant-based diet inspired by the idea that human ancestors mainly consumed roughage — may not be so good at suppressing appetite, according to new research conducted on gut bacteria.
In the study, researchers looked at gut bacteria taken from people and from primates called gelada baboons, and found that bacteria fed with predigested grass produced a smaller amount of compounds called short-chain fatty acids, which trigger the production of appetite-reducing gut hormones, compared with the bacteria fed with predigested potatoes.
"We didn't find any suggestion that people should start eating grass and that [doing so] would help control their appetite," said study author Timothy Barraclough, a professor of evolutionary biology at Imperial College London.
Moreover, the findings do not support the idea that weight gain results from the mismatch between the foods people tend to eat these days and what humans' ancestors used to eat, the researchers said. [11 Surprising Things That Can Make Us Gain Weight]
According to paleontological evidence, the diet of early hominins included considerably more plants than the contemporary human diet, the researchers wrote in the study. But in the study, "it was really the potato diet that was leading to the production of more of these [appetite-suppressing] compounds and [had] a bigger effect on the hormone pathways than the grass," Barraclough said.
"Another interesting thing was that although the baboons mainly eat grass, they seem to be producing more of these [appetite-suppressing] products on the potato diet as well," Barraclough told Live Science.
So does this mean that a plant-based, paleo diet has no benefits? Not necessarily.
The paleo diet is high in fiber, which brings a variety of benefits, study author Glenn Gibson, a professor of food microbiology at the University of Reading in the United Kingdom, told Live Science in an email. "These [benefits] still stand, and can't really be contested."
The benefits include helping food move through the gut, and helps maintain a healthy community of gut bacteria, he said.
To obtain the gut bacteria for the study, the researchers took fecal bacterial samples from three human vegetarian volunteers and three gelada baboons, which are the only modern primates that eat mainly grasses.The researchers wanted to imitate the real-life digestion process and the environment in the human and baboon guts as closely as possible, so they fed the bacteria either grass or potato that had been partially digested.
The researchers also found that the appetite-suppression process that occurs in the gut turned out to be more complicated than expected.
"One of the goals is to find which chemicals are having the biggest effect, and then find ways of delivering those to the point of action," in the form of supplement capsules or, for instance, prebiotics, Barraclough said.