In a new study, those who went paleo reported an increase in tiredness, headaches and, uh, diarrhea.

By Gillie Houston
Updated May 24, 2017
Skirt Steak with Salsa Verde and Ricotta Salata

The paleo diet has built a massive number of adherents, but a new study out of Australia seems to show it could do harm to your digestive health.

Researcher Angela Genoni of the Edith Cowan University School of Medicine and Health Sciences recently set out to determine how the paleo way of eating impacted the body differently from the Australian Guide to Healthy Eating (AGHE), which recommends grains, legumes, dairy and processed foods (all of which aren't allowed on the caveman-style diet). The paleo diet, which is meant to replicate what early humans consumed during the Paleolithic era, encourages the consumption of unprocessed, protein-rich foods like eggs and nuts.

Throughout the four week study, participants—which included 39 healthy women between the ages of 34 and 60 with an average BMI of 27—were assigned two different diet plans: one group sticking to paleo, and the others following the AGHE guidelines. Those who cut grains and other non-paleo ingredients from their diets reported an increase in tiredness and headaches, and experienced more episodes of diarrhea, likely due to the diet's impact on their gut bacteria.

According to Genoni, "fiber acts as a prebiotic; they are food for the bacteria, and a lot of food for them means they can flourish." These findings come as a follow-up to the researcher's previous study on the paleo diet in May, which determined that while the ancient eating plan lead to weight loss, it had no beneficial impact on blood glucose or cholesterol levels.

However, another recent study claims that the caveman's way of eating could in fact lead to weight gain. No word yet on how these less-than-positive reports could impact paleo trendsetter Bernie Sanders's dedication to the diet.

For those still sold on the benefits of going paleo, these dinner recipes are right up your alley.