Lean beef: take it or leave it for weight loss

A high protein intake has been identified^[1] as a common feature of successful weight loss interventions. It promotes satiety and reduces the loss of lean body mass with dieting. However, controversy has ensued over appropriate food sources of protein. From a nutritional standpoint, meat, eggs, and dairy are considered^[2] the most bioavailable sources of dietary protein due to their complete amino acid profiles and high digestibility. As shown in Figure 1, meat consumption in the U.S. has increased^[3] by about 67% over the last century, with 58% of current meat intake being red meat, 32% poultry, and 10% fish.

Several studies have investigated the impact of different food sources of protein on body composition and cardiometabolic health. We have discussed some of these in past ERD issues, such as one study^[4] comparing two high-protein diets based on either animal protein or plant protein (ERD #31, Volume 1) and one study^[5] comparing three DASH diets differing in their protein and red meat content (ERD #12, Volume 1). Other studies^[6][7] have also investigated the health effects of red meat consumption in the context of a healthy dietary pattern. Collectively, these studies have suggested that red meat does not affect weight loss and cardiometabolic risk factors any differently from other sources of protein in the context of a healthy diet. The focus on red meat is understandable, considering it represents a majority portion of meat intake in the U.S. and has been associated with cardiovascular disease morbidity^[8] and mortality^[9]. Although the short-term randomized trials mentioned above have not been able to confirm these observations since, by their nature, they can’t examine these long-term outcomes, no randomized controlled trial has yet to compare red meat to other animal proteins in the context of a high-protein weight-loss diet. It is therefore important to test whether red meat undermines weight loss efforts. The study under review is a randomized controlled trial that was designed to fill this knowledge gap.

High-protein diets are effective for weight loss, but uncertainty exists as to where the protein should be coming from. Since red meat represents a significant portion of total meat intake in the U.S. and is thus an important contributor to this population’s total protein intake, the study under review compared two high-protein weight-loss diets that differed only in their red meat content so as to discover if these diets differentially affected weight loss and cardiometabolic health.