Abstract
Short-term energy deficit strategies are practiced by weight class and physique athletes, often involving high protein intakes to maximize satiety and maintain lean mass despite a paucity of research. This study compared the satiating effect of two protein diets on resistance-trained individuals during short-term energy deficit. Following ethical approval, 16 participants (age: 28 ± 2 years; height: 1.72 ± 0.03 m; body-mass: 88.83 ± 5.54 kg; body-fat: 21.85 ± 1.82%) were randomly assigned to 7-days moderate (PROMOD: 1.8 g·kg−1·d−1) or high protein (PROHIGH: 2.9 g·kg−1·d−1) matched calorie-deficit diets in a cross-over design. Daily satiety responses were recorded throughout interventions. Pre-post diet, plasma ghrelin and peptide tyrosine tyrosine (PYY), and satiety ratings were assessed in response to a protein-rich meal. Only perceived satisfaction was significantly greater following PROHIGH (67.29 ± 4.28 v 58.96 ± 4.51 mm, p = 0.04). Perceived cravings increased following PROMOD only (46.25 ± 4.96 to 57.60 ± 4.41 mm, p = 0.01). Absolute ghrelin concentration significantly reduced post-meal following PROMOD (972.8 ± 130.4 to 613.6 ± 114.3 pg·mL−1; p = 0.003), remaining lower than PROHIGH at 2 h (−0.40 ± 0.06 v −0.26 ± 0.06 pg·mL−1 normalized relative change; p = 0.015). Absolute PYY concentration increased to a similar extent post-meal (PROMOD: 84.9 ± 8.9 to 147.1 ± 11.9 pg·mL−1, PROHIGH: 100.6 ± 9.5 to 143.3 ± 12.0 pg·mL−1; p < 0.001), but expressed as relative change difference was significantly greater for PROMOD at 2 h (+0.39 ± 0.20 pg·mL−1 v −0.28 ± 0.12 pg·mL−1; p = 0.001). Perceived hunger, fullness and satisfaction post-meal were comparable between diets (p > 0.05). However, desire to eat remained significantly blunted for PROMOD (p = 0.048). PROHIGH does not confer additional satiating benefits in resistance-trained individuals during short-term energy deficit. Ghrelin and PYY responses to a test-meal support the contention that satiety was maintained following PROMOD, although athletes experiencing negative symptoms (i.e., cravings) may benefit from protein-rich meals as opposed to over-consumption of protein.
Highlights
Weight loss is an essential component of success for many strength athletes, as well as individuals involved in general strength training
Whilst protein was generally maintained during PROMOD compared with pre-intervention intakes, PROHIGH resulted in an expected increase in relative protein from 1.84 ± 0.15 to 2.89 ± 0.01g·kg−1 ·d−1 (F = 78.29(diet x time), p < 0.0001, ηp2 = 0.84)
Whilst the results from this study indicate that a PROMOD preferentially influences hormonal responses to a test-meal, it is evident that perceived responses were comparable between intervention diets
Summary
Weight loss is an essential component of success for many strength athletes, as well as individuals involved in general strength training. Weight class athletes restrict dietary energy intake typically for 7–21 days prior to a competition [1], or during phases of training, to enhance the strength to body-mass ratio, improve body composition, and increase the competitive advantage in weight class events [2]. For physique/ bodybuilding athletes, similar practices of caloric restriction often occurs for longer time periods i.e., >12 weeks to reach a very low body fat percentage, often going below 5%. During dieting phases many athletes may substantially increase their protein intake, as this practice has been shown to be beneficial to maintain lean mass whilst reducing body-fat [4,5,6,7,8,9,10,11,12,13]. There is, controversy as to whether substantially higher protein intakes ranging from 2.3 to 3.1 g·kg−1 ·d−1 may yield optimal results [13] with evidence that resistance-trained athletes consume protein intakes as high as 4.3 g·kg−1 ·d−1 [18]
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