There are several major diet types interspersed with a multitude of subtypes. This creates a maze of conflicting principles that may be difficult for the general public and practitioners to navigate. Compounding the confusion is the continued propagation of fad diets across a range of media outlets, replete with unfounded practices. Therefore, it is important to examine the scientific evidence in a systematic way in order to devise recommendations to guide healthcare practitioners, coaches (including trainers, dietitians, and sports nutritionists), athletes, and the general public regarding all of the above. The purpose of this position stand is to provide clarity on the effects of various diets on body composition.
Stefansson wrote extensively about these experiences in both the scientific literature and in books for the lay public . One of the main themes of his writing was the adaptation of the Inuit culture to survive as nomadic groups in the arctic on a diet consisting solely of the products of hunting and fishing. Coming as it did in the same time period that the science of nutrition was blossoming with the discovery and characterization of vitamins (eg, the first vitamin to be chemically defined was thiamin by Funk in 1911), Stefansson's claim that one could live and function well on the products of just one food group caused tremendous controversy .
The possibility raised by the first study of improved endurance time after keto-adaptation was not substantiated by the second study employing highly trained athletes without the complicating variable of major weight loss. It is thus likely that the increased endurance time in the Vermont study was due to improved efficiency (ie, less hobbling from a backpack than from an equal weight of internal body fat) and/or improved acclimation to the endurance test procedure. Such acclimation would not be expected in the second study, as the highly trained bicycle racers were well conditioned to the stationary ergometer at the start of the study. It is also worth noting that the bicycle racers remained weight stable (excepting the half kilogram of reduced muscle glycogen) across the 4 weeks of the EKD, which was equi-caloric with the baseline diet. Although 4 weeks is a relatively short period to assess small differences in energy efficiency between diets, this observation implies that there was no great reduction in the efficiency of energy metabolism after keto-adaptation.
Because of the unfounded fears that carbohydrate is fattening or the belief that you need a high-protein diet to build muscle or a high-fat diet for endurance, many athletes today are skimping on carbohydrate foods. Some go on the paleo diet or keto diet; others go gluten free. The resulting low-carbohydrate intake can potentially hurt performance; it contrasts sharply with the diet of 2.5 to 4.5 grams of carbohydrate per pound of body weight (5 to 10 g/kg)—or 55 to 65 percent carbohydrate—recommended by most exercise and health professionals for people who train for one to three hours a day.
A study published in the American Journal of Clinical Nutrition found that not only did the Mediterranean Diet lead to weight loss, but it was also the easiest for people to adhere to when compared to intermittent fasting and the paleo diet. (6) When adhered to, the diet has also been found to reverse symptoms of diabetes and cardiovascular diseases. (7)
I see all versions of the Paleo diet as a great way to make first steps towards a truly traditional diet. These days anyone can easily find many healthy and delicious recipes in Paleo cookbooks and blogs to make the transition from a SAD diet to a better one as tasty and as easy as possible.
Loren Cordain, S. Boyd Eaton, and Melvin Konner have published estimated composition of Paleolithic diets based on extensive investigation of existing hunter-gatherer cultures. I have to think that Cordain took that into account in his latest book on the paleo diet. 2b1af7f3a8