Short term effects of a ketogenic diet on body weight, energy expenditure and exercise capacity in rodents

Given the current obesity epidemic successful strategies need to be developed, aimed at reducing bodyweight and increasing physical activity. The present investigation was designed to examine the effects of consuming a low-carbohydrate ketogenic diet on body weight, energy expenditure (EE) and exercise capacity in rodents. Male wistar rats were fed either a ketogenic diet (KD n=11) or normal lab chow (CH n=12). The animals were pair fed thus ensuring that all animals had the same daily energy intake. All animals were trained for 21 days using a forced running wheel. The training schedule was incremental, every three days the time and/or the speed of the wheel were increased. Following the training period all animals took part in a performance test (time to exhaustion). Consuming a KD resulted consistently in an approximately 14% higher post-exercise energy expenditure (kcal/kg*h) following 14 days exposure to the diet compared with controls (d14–16 KD 8.21±0.15, CH 7.18±0.35 p=0.02, d17–19 KD 8.06±0.27, CH 6.9±0.24 p=0.02, d20–22 KD 8:34±0:16, CH 7.33±0.21, p=0.004, d 23–24 KD 7.88±0.17, CH 6.86±0.29 p=0.02, d25–28 KD 8.08±0.17, CH 6.86±0.48 p=0.04). Endpoint body weight was significantly different between the two groups, with the KD weighing less (352.3±13.6g) in comparison to the CH group (398.5±24.3g) despite consuming an equicalorific diet (p<0.01). Consuming a KD did not impair exercise capacity, as both groups demonstrated identical abilities to perform exercise in a performance test at the end of the study (CH129±12mins, KD118±15mins, p>0.05). The results of the current investigation contribute to our knowledge of possible physiological mechanisms underlying the effectiveness of low-carbohydrate diets. An increased caloric cost of exercise may contribute, in part, to the weight loss observed. In addition it appears that low-carbohydrate diets result in significant changes to body weight without reducing „habitual“ energy intake. In conclusion, combining low-carbohydrate ketogenic diets with physical activity may have a synergistic effect.