Protein intake and body recomposition in older women Original paper

Body recomposition is the process of increasing muscle mass and reducing fat mass. Resistance training along with higher protein intake is the cornerstone of body recomposition. This study analyzed the effects of low, moderate, and high protein intakes in older women following a resistance training program.

This retrospective analysis assessed evidence from 6 studies in 130 untrained older (68.7 years of age on average) physically independent women from the Active Aging Longitudinal Study who were not taking hormone replacement therapy. The participants were divided into tertiles according to their protein intake: low protein (LP, 45 participants, ≤ 0.92 grams of protein per kilogram of body weight per day or 0.92 grams/kg/day), moderate protein (MP, 42 participants, ≥ 0.93 and ≤ 1.16 grams/kg/day), and high protein (HP, 43 participants, > 1.16 grams/kg/day). No participants were eating vegetarian or vegan diets, and the main source of protein came from animals.

The participants completed a 24-week (3 sessions per week) full-body resistance training program. Body composition was measured at baseline and at the end of the studies. The participants' habitual dietary intakes were recorded using the 24-hour dietary recall method in the first and last 2 weeks of the intervention.

The HP group had a lower BMI than the LP and MP groups at baseline. They also had a greater total calorie intake compared to the LP group.

Muscle mass increased across all groups from baseline, but the HP and MP groups had greater increases in muscle mass than the LP group (LP = +2.3%, MP = +5.4%, and HP = +5.1%). All groups saw reductions in fat mass (LP = −1.7%, MP = −3.7%, and HP = −3.1%).

The combined body composition changes from baseline to the end of the intervention showed that the HP and MP groups had greater favorable changes than the LP group.

The HP group averaged a protein intake of 1.34 grams/kg/day, which is less than recommended for muscle mass gains (≥ 1.6 grams/kg/day). The HP group may have shown better results had they increased their intake to the recommended amount. Also, the participants' physical activity outside of the resistance training program was not taken into account, and therefore, we cannot know whether there were meaningful differences in energy expenditure between the groups.