Are Individuals with Type 2 Diabetes More Likely to Burn Carbohydrate Versus Fat for Energy?

Abstract

Impaired fat oxidation has been associated with increased plasma free fatty acid concentrations, ectopic fat deposition and insulin resistance, which may contribute to the development of Type 2 Diabetes (T2D). The objective of this pilot study was to determine whether individuals with T2D presented with a greater proportion of carbohydrate (CHO burners) versus fat (fat burners) oxidation over a 24 hour period (RQ24). A second objective was to determine whether metabolic variables and metabolic flexibility (ability to shift from fat to CHO oxidation) differed between CHO and fat burners. RQ24 was measured in 10 participants with T2D using a whole body calorimetry unit. Participants were fed a standard diet (50% CHO, 20% protein, 30% fat) that was individually prescribed to maintain energy balance. Fasting and postprandial biochemical measures and body composition were assessed. Participants were classified as CHO burners if RQ24 ≥ 0.880 (n=7) and fat burners if RQ24 ≤ 0.865 (n=3). Fat burners had higher fasting plasma glucose concentrations than CHO burners (p = 0.045), while CHO burners showed a trend toward a greater central fat mass (p = 0.071) and higher systolic blood pressure (p = 0.052). Metabolic flexibility was not significantly different between CHO and fat burners. Differences in RQ24 existed in participants with T2D fed a standard diet, suggesting that there was a greater number that exhibited a higher proportion of CHO than fat oxidation over a 24 hour period. Fasting glucose, central body fat and resting blood pressure were associated with these differences.