This is the first study I’m aware of that looked specifically at female physique athletes and the effects of a higher protein intake, and comes from Dr. Bill Campbell’s lab via the University of South Florida, Performance & Physique Enhancement Laboratory, which I gave a talk at recently and presented at conferences. It’s interesting to note they found increased LBM with higher protein off season:
Effects of a high (2.4 g/kg) vs. low/moderate (1.2 g/kg) protein intake on body composition in aspiring female physique athletes engaging in an 8-week resistance training program
Bill I. Campbell, Danielle Aguilar, Andres Vargas, Laurin Conlin, Amey Sanders, Paola Fink-Irizarry, Layne Norton, Ross Perry, Ryley McCallum, Matthew R. Wynn, Jack Lenton.
University of South Florida, Performance & Physique Enhancement Laboratory, Tampa, FL, USA
Aspiring female physique athletes are often encouraged to ingest relatively high levels of dietary protein in conjunction with their resistance-training programs. However, there is little to no research investigating higher vs. lower protein intakes in this population. The purpose of this investigation was to compare the effects of a high protein diet vs. a low protein diet in resistance trained, aspiring female physique athletes.
17 resistance-trained female subjects (21.2±2.1 years; 165.1±5.1 cm; 61±6.1 kg) participated in this investigation. At baseline and following 8-weeks of a periodized daily undulating resistance-training program (DUP), participants were assessed for body composition (body weight [BW], fat mass [FM], body fat % [BF%], and lean body mass [LBM]). After baseline testing, participants were matched according to total FM and randomized to the high protein group (HP; n = 8) or the low/moderate protein group (LP; n = 9). Participants in the high protein group were instructed to ingest at least 2.4 grams of protein/kg body mass per day and participants in the low protein group were instructed to ingest no more than 1.2 grams of protein/kg body mass. There were no restrictions or guidelines placed on dietary CHO or Fat intake during the study intervention for either group. Body composition was assessed via ultrasound (A mode, 2.5-MHz transmitter). The DUP program consisted of two lower body and two upper body workouts conducted a total of 4 times per week for 8 weeks. Data were analyzed via a 2-factor [2x2] between-subjects repeated measures analysis of variance (ANOVA). The criterion for significance was set at p ≤ 0.05.
No differences existed between the two groups for any body composition measure at baseline. The repeated measures ANOVA revealed a significant group x time interaction for lean body mass (p = 0.009) favoring the high protein group. Specifically, lean body mass increased from 47.1 ± 4.5kg to 49.2 ± 5.4kg and from 48.1 ± 2.7kg to 48.8 ± 2 in the high and low protein groups, respectively. There were no differences between the groups for BW (HP: Pre = 61.2 ± 7.9kg, Post = 62.2 ± 8.2kg, LP: Pre = 61.4 ± 4.4kg, Post = 61.2 ± 4.6kg, p = 0.120); FM (HP: Pre = 14.1 ± 3.6kg, Post = 13.0 ± 3.3kg, LP: Pre = 13.2 ± 3.7kg, Post = 12.5 ± 3.0kg, p = 0.678), or BF% (HP: Pre = 22.7 ± 3.0%, Post = 20.7 ± 3.1%, LP: Pre = 21.4 ± 5.2%, Post = 20.3 ± 3.9%, p = 0.349).
In aspiring female physique athletes, it appears as if a higher protein diet (at least 2.4g/kg day) is superior to a lower protein diet in terms of increasing lean body mass in conjunction with a DUP program. It is important to note that these findings were observed during a non-dieting phase of training – equivalent to a physique athlete’s off-season. There does not appear to be any advantages to a higher protein diet in relation to inducing fat loss under the same conditions.