Effects of a Short-Term Carbohydrate-Restricted Diet on Strength and Power Performance

Abstract

The purpose of the study was to examine the effects of switching from a habitual diet to a carbohydrate-restricted diet (CRD) on strength and power performance in trained men (n = 16) and women (n = 15). Subjects performed handgrip dynamometry, vertical jump, 1RM bench press and back squat, maximum-repetition bench press, and a 30-second Wingate anaerobic cycling test after consuming a habitual diet (40.7% carbohydrate, 22.2% protein, and 34.4% fat) for 7 days and again after following a CRD (5.4% carbohydrate, 35.1% protein, and 53.6% fat) for 7 days. Before both testing sessions, body weight and composition were examined using bioelectrical impedance analysis. Three 2 × 2 multiple analyses of variance were used to compare performance variables between the habitual diet and CRD. Subjects consumed significantly fewer (p < 0.05) total kilocalories during the CRD (2,156.55 ± 126.7) compared with the habitual diet (2,537.43 ± 99.5). Body mass decreased significantly (p < 0.05). Despite a reduction in body mass, strength and power outputs were maintained for men and women during the CRD. These findings may have implications for sports that use weight classes, and in which strength and power are determinants of success. A CRD may be an alternative method for short-term weight loss without compromising strength and power outputs. The use of a 7-day CRD could replace weight loss methods employing severe dehydration before competition.

Ketogenic diet benefits body composition and well-being but not performance in a pilot case study of New Zealand endurance athletes

“…This outcome was unsurprising and comparable to findings in previous research on both strength and endurance athletes [13–15]. Initial weight reduction can be associated with a loss in body water through glycogen depletion, [16, 17], and this was also likely the case in this study; however fat loss was evident as per skinfold changes.…”

Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation

“…While these diets have not been sufficiently studied in bodybuilders, some study of ketogenic diets has occurred in resistance trained populations. In an examination of the effects of a 1 week ketogenic diet (5.4% of calories from carbohydrate) in subjects with at least 2 years of resistance training experience, Sawyer et al [62] observed slight decreases in body fat among female participants and maintenance or slight increases in measures of strength and power among both male and female participants. However, it is difficult to draw conclusions due to the very short term nature of this study and due to an ad libitum implementation of the ketogenic diet.…”

The Ketogenic Diet and Sport

“…It takes 7 d to adapt, leaving just a few days in which any effects may be seen V thus, a 2-wk protocol would be marginal at best. Thus, athletes should program a KD for weight loss at least 2 wk before competition, even though a recent article by Sawyer and colleagues (33) reported that power output was not affected negatively in 31 trained individuals after only 7 d of a KD (5.4% carbohydrate, 35.1% protein, and 53.6% fat); b) whether or not electrolyte supplements were given V during a KD, sodium and potassium need to be supplied to maintain tissue function and nitrogen balance (27); c) the amount of protein given V during a KD, the need for protein is higher because of gluconeogenesis; thus, a low intake of protein may affect negatively the athlete's muscle mass.…”