In November of 2014, the conducted by Swedish researchers comparing Paleo-inspired diets with those based on the Nordic Nutrition Recommendations (NNR).1 The NNR are comparable to the USDA’s dietary guidelines, emphasizing low-fat dairy and and recommending a macronutrient distribution of 55-60% of calories from carbohydrates, 25-30% from fat, and 15% from protein. The macronutrient distribution used in this study to represent the Paleo diet was 30% carbohydrates, 40% fat, and 30% protein.
The researchers grouped 49 overweight or obese postmenopausal women into the Paleo and NNR groups, tracking their progress over two years. They were primarily serving how these diets influence glucocorticoid metabolism. Glucocorticoids are stress hormones that modulate various metabolic, inflammatory, and cardiovascular processes.2 Abnormal glucocorticoid metabolism is associated with metabolic syndrome and obesity.
Cortisol, the principal active glucocorticoid, is secreted by the adrenal glands and converted to cortisone, the inert form.3 One of the enzymes responsible for this conversion is called 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Obese individuals demonstrate increased activity of 11β-HSD1 in subcutaneous adipose tissue (SAT), which is fatty tissue directly under the skin. The researchers hypothesized that diet-induced weight loss results in decreased expression of 11β-HSD1 in SAT and thus a reversal of the abnormal glucocorticoid metabolism common to obese patients.
The study’s participants were observed at baseline, after 6 months, and after 24 months. Both groups lost weight and decreased BMI, waistline measurements, and total body fat throughout the study. The Paleo group had greater reductions after 6 months, but after 24 months there were no significant differences between the groups. Both groups also demonstrated decreased activity of 11β-HSD1 in SAT. The researchers noted, “We did not find any major difference between diets on glucocorticoid metabolism.”4
So what does this study tell us? The Paleo diet performed better than NNR after 6 months, but after two years, it seems neither diet had any advantages over the other. It’s important, however, to look closer at the structure of the study. Every two months, participants attended sessions with dietitians to ensure compliance with their respective diets. Food journals and urine samples were used for monitoring and measuring food intake. An anomaly, however, pointed out by the researchers, was that urinary nitrogen levels were not higher in the Paleo group (as they should have been) at any time during the study, “indicating that the actual intake of protein was similar in both diet groups.”5 The Paleo group, however, was instructed to eat 30% of calories as protein, double the amount of the NNR group.
Also, Paleo participants were instructed to eat 40% of calories as fat, “with a high proportion of mono- and polyunsaturated fatty acids (MUFAs and PUFAs).” An authentic Paleo diet, however, would have higher proportion of saturated fatty acids and MUFAs, with only very small amounts of PUFAs. So, the “Paleo diet” and the low-fat, high-carb, grain-centric diet fared similarly, but were Paleo participants following an authentic Paleo diet? This seems doubtful. Nevertheless, this study represents an important advance in our understanding of how diets influence stress hormones. Follow-up studies will hopefully ensure greater compliance to authentic Paleo diets.
Christopher James Clark, B.B.A.
Christopher James Clark, B.B.A. is an award-winning writer, consultant, and chef with specialized knowledge in nutritional science and healing cuisine. He has a Business Administration degree from the University of Michigan and formerly worked as a revenue management analyst for a Fortune 100 company. For the past decade-plus, he has been designing menus, recipes, and food concepts for restaurants and spas, coaching private clients, teaching cooking workshops worldwide, and managing the kitchen for a renowned Greek yoga resort. Clark is the author of the critically acclaimed, award-winning book, .
 Stomby, A., et al. (October 2014). Diet-induced weight loss has chronic tissue-specific effects on glucocorticoid metabolism in overweight postmenopausal women. International Journal of Obesity. Retrieved from //www.nature.com/ijo/journal/vaop/ncurrent/full/ijo2014188a.html
 Wang, M. (February 2005). The role of glucocorticoid action in the pathophysiology of the Metabolic Syndrome. Nutrition & Metabolism, 2(3). Retrieved from //www.nutritionandmetabolism.com/content/2/1/3
 Ibid, Wang.
 Ibid, Stomby.
 Ibid, Stomby.