The anabolic skeletal muscle response to acute resistance exercise is not impaired in rats fed a ketogenic diet

Background

Many individuals that resistance train consume a typical Western diet (WD) comprised of protein, carbohydrates (many of which are sugar), and fat. Recent enthusiasm has surrounded the use of a ketogenic diet for weight loss and muscle sparing, although it is uncertain as to whether low carbohydrate diets can optimize the anabolic response to resistance training.

Methods

This study examined the effects of KD versus WD on the anabolic response to resistance exercise using a rodent leg-kicking resistance exercise model. Male Sprague-Dawley rats (~9-10 weeks of age) were provided isocaloric amounts of either a KD (5.2 kcal/g, 20.2% protein, 10.3% carbohydrate, 69.5% fat; n = 30) or WD (4.5 kcal/g, 15.2% protein, 42.7% carbohydrate, 42.0% fat; n = 32) for 6 weeks. During week 7, the right-leg plantarflexor muscles of each rat were acutely exercised under isoflurane anesthesia using high-frequency electrical stimulations (4 sets of 8 repetitions with 2 min recovery between sets). Rats were then sacrificed at 90 min (n = 8 per group), 180 min (n = 8 per group), or 270 min (n = 8 per group) following exercise and intraperitoneal puromycin injections were provided 30 min prior to each sacrifices as a tracer for muscle protein synthesis (MPS). A subset of unexercised limbs from WD (n = 8) and KD (n = 8) were used as a non-exercise (non-EX) control comparison.

Results

There was a main time effect for MPS, as it was significantly greater at 90, 180 and 270 min in both groups versus the non-EX condition (p < 0.001), although there was no between group effect (p = 0.59) or group*time interaction (p = 0.87). There was a main time effect for phosphorylated (p)-4E-BP1 (Thr37/46), as it was significantly greater at 90, 180 and 270 min in both groups versus the non-EX condition (p = 0.001), although there was no between group effect (p = 0.85) or group*time interaction (p = 0.93). There was a main time effect for p-rps6 (Ser235/236), as it was significantly greater at 90, 180 and 270 min in both groups versus the non-EX condition (p = 0.002), although there was no between group effect (p = 0.99) or group*time interaction (p = 0.79). There was no time effect (p = 0.31), between group effect (p = 0.42) or group*time interaction (p = 0.22) for p-AMPKα (Thr172).

Conclusions

These data demonstrate that rats fed a ketogenic diet present a similar anabolic response to resistance exercise compared to rats fed a Western diet.