Effects of Two Months of Very Low Carbohydrate Ketogenic Diet on Body Composition, Muscle Strength, Muscle Area, and Blood Parameters in Competitive Natural Body Builders

Abstract

Background: Ketogenic diet (KD) is a nutritional approach that restricts daily carbohydrates, replacing most of the reduced energy with fat, while maintaining an adequate quantity of protein. Despite the widespread use of KD in weight loss in athletes, there are still many concerns about its use in sports requiring muscle mass accrual. Thus, the present study sought to investigate the influence of a KD in competitive natural body builders. Methods: Nineteen volunteers (27.4 ± 10.5 years) were randomly assigned to ketogenic diet (KD) or to a western diet (WD). Body composition, muscle strength and basal metabolic rate were measured before and after two months of intervention. Standard blood biochemistry, testosterone, IGF-1, brain-derived neurotrophic factor (BDNF) and inflammatory cytokines (IL6, IL1β, TNFα) were also measured. Results: Body fat significantly decreased in KD (p = 0.030); whilst lean mass increased significantly only in WD (p < 0.001). Maximal strength increased similarly in both groups. KD showed a significant decrease of blood triglycerides (p < 0.001), glucose (p = 0.001), insulin (p < 0.001) and inflammatory cytokines compared to WD whilst BDNF increased in both groups with significant greater changes in KD (p < 0.001). Conclusions: KD may be used during body building preparation for health and leaning purposes but with the caution that hypertrophic muscle response could be blunted.

Keywords: health; ketogenic diet; resistance training; strength.

Figure 1

Study design. ICF, Informed consent form signed; BIA, Bioelectrical Impendence Analysis; REE, Basal metabolism; RER, respiratory quotient; 1 RM, 1 repetition-maximum test; WD, Western diet, KD, Ketogenic Diet.

Figure 2

Body composition results after 8 weeks of diet. (A) body weight; (B) Fat Mass; (C) Fat Free Mass. * significantly different from pre-value (p < 0.05); ¶ time × diet interaction (p < 0.05). KD, ketogenic diet group; WD, western diet group.

Figure 3

Insulin sensitivity results. (A) plasma glucose concentration; (B) plasma insulin concentration. * significantly different from pre-value (p < 0.05); # significantly different from KD group (p < 0.05); ¶ time × diet interaction (p < 0.05). KD, ketogenic diet group; WD, western diet group.

Figure 4

Inflammatory markers and brain-derived neurotrophic factor (BDNF). (A) IL-6 concentration; (B) TNF-α concentration; (C) BDNF concentration. * significantly different from pre-value (p < 0.05); # significantly different from KD group (p < 0.05); ¶ time × diet interaction (p < 0.05). KD, ketogenic diet group; WD, western diet group.