Quality protein intake is inversely related with abdominal fat

Abstract

Dietary protein intake and specifically the quality of the protein in the diet has become an area of recent interest. This study determined the relationship between the amount of quality protein, carbohydrate, and dietary fat consumed and the amount of times the ~10 g essential amino acid (EAA) threshold was reached at a meal, with percent central abdominal fat (CAF). Quality protein was defined as the ratio of EAA to total dietary protein. Quality protein consumed in a 24-hour period and the amount of times reaching the EAA threshold per day was inversely related to percent CAF, but not for carbohydrate or dietary fat. In conclusion, moderate to strong correlations between variables indicate that quality and distribution of protein may play an important role in regulating CAF, which is a strong independent marker for disease and mortality.

Introduction

Dietary protein intake and specifically the quality of the protein in the diet has become an area of recent interest, particularly when combined with resistance training (for a thorough review the reader is directed to ref. [1]). Quality of protein is defined as the ratio of essential amino acids (EAA) to dietary protein in grams. The dietary reference intake (DRI) includes no specific recommendation regarding the type of dietary protein consumed or distribution of that dietary protein throughout the day. Approximately 10 g of EAA, at a meal, maximally stimulates muscle protein synthesis (MPS) [2]. EAA intake beyond this level does not appear to result in an additional anabolic response [3].

Studies have demonstrated that the consumption of dietary protein above the DRI has been associated with favorable changes in body composition [4]. Proposed mechanisms include the maintenance or accretion of lean mass and/or increased thermogenesis and satiety [5]. A 5-year prospective study found that protein intake was inversely related to changes in waist circumference [6]. Waist circumference is a surrogate marker for abdominal obesity, and this type of obesity is associated with significant risks of developing type 2 diabetes, coronary artery disease, stroke, and a higher risk of mortality, even after adjustments for general obesity [6]. However, the quality of the protein source consumed and the distribution of that protein throughout the day with respect to central abdominal fat (CAF) have not been investigated in free living conditions.

We sought to determine the relationship between the amount of quality protein consumed in 24-hours and the amount of times the ~10 g EAA threshold was reached at a meal, with respect to percent CAF. This is a secondary analysis using a data set from a previously reported paper on quality protein, overall body composition (lean mass and total body fat), and bone health [7].