Paleo plus exercise: not the perfect match from the past?

Type 2 diabetes is a metabolic disorder characterized by a resistance to insulin, leading to a reduced ability of muscle and fat cells to properly uptake glucose and consequently resulting in chronically high levels of blood glucose. The prevalence of both type 1 and type 2 diabetes is estimated to be 12%-14%^[1] of the U.S. population. Globally, recent estimates indicate a prevalence of 8.8% in 2015 that is expected to grow^[2] to 10.4% by 2040, with 90% of all cases^[3] estimated to be type 2 diabetes.

Obesity^[4], particularly abdominal obesity^[5], is very strongly associated with type 2 diabetes. Type 2 diabetes has also been shown to be correlated with non-alcoholic fatty liver disease^[6], visceral fat, inflammatory cytokines^[7] like interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFα), and an elevated intramyocellular lipid (IMCL) content^[8] (i.e. fat in the skeletal muscle).

Diet and lifestyle interventions have been shown to be very effective^[9] at sustainably reducing the incidence of type 2 diabetes. These interventions, which require significant diet and lifestyle modifications, can even be more effective^[10] than first line diabetes drugs like metformin at reducing the risk of developing type 2 diabetes. A recent meta-analysis^[11] concluded that interventions with diet modification and exercise that included both aerobic and resistance training were the most effective at reducing biomarkers of type 2 diabetes. However, limited evidence suggests that interventions that include both exercise and diet perform as well as^[12] exercise alone.

Public interest in Paleolithic-style diets has increased dramatically over the past several years. Just like the "Mediterranean diet," the "Paleo diet" is not a detailed dietary prescription, but rather a set of rules that requires one to consume a diet consisting largely of meats, vegetables, fruits, nuts, and tubers, while excluding cereal grains, dairy, and products with added salt and sugar.

In people with type 2 diabetes, the Paleo diet has performed favorably against diets based on national dietary guidelines^[13], the Nordic Nutrition Recommendations^[14], and a standard low-fat diet^[15] in clinical trials. The study under review would be the first to examine the differences between a Paleo diet alone and a Paleo diet with a combination of aerobic and resistance exercise.

Type 2 diabetes is a growing problem in the U.S. and globally. Treating type 2 diabetes with diet and exercise has been shown to be very effective, but few studies have focused on treatments with a Paleolithic-style diet and none have examined the effect of adding exercise to this diet and the differential effects on liver fat and intramuscular fat stores.