Impact of Ketogenic Diet on Body Composition during Resistance Training among Untrained Individuals

Problems and Opportunities in the use of Bioelectrical Impedance Analysis for Assessing Body Composition During Ketogenic Diets: A Scoping Review

PURPOSE OF THE REVIEW

The use of bioelectrical impedance analysis (BIA) for monitoring body composition during the ketogenic diet has experienced a rapid surge. This scoping review aimed to assess the validity of procedures applying BIA in the ketogenic diet and to suggest best practices for optimizing its utilization.

RECENT FINDINGS

We conducted a systematic scoping review of peer-reviewed literature involving BIA for assessing body composition in individuals adhering to a ketogenic diet. Searches of international databases yielded 1609 unique records, 72 of which met the inclusion criteria and were reviewed. Thirty-five studies used foot-to-hand technology, 34 used standing position technology, while 3 did not declare the technology used. Raw bioelectrical parameters were reported in 21 studies. A total of 196 body mass components were estimated, but predictive equations were reported in only four cases. Most research on BIA during ketogenic diets did not report the equations used for predicting body composition, making it impossible to assess the validity of BIA outputs. Furthermore, the exceedingly low percentage of studies reporting and analyzing raw data makes it challenging to replicate methodologies in future studies, highlighting that BIA is not being utilized to its full potential. There is a need for more precise technology and device characteristics descriptions, full report of raw bioelectrical data, and predictive equations utilized. Moreover, evaluating raw data through vectorial analysis is strongly recommended. Eventually, we suggest best practices to enhance BIA outcomes during ketogenic diets.

Effects of the Ketogenic Diet on Muscle Hypertrophy in Resistance-Trained Men and Women: A Systematic Review and Meta-Analysis

Reviews focused on the ketogenic diet (KD) based on the increase in fat-free mass (FFM) have been carried out with pathological populations or, failing that, without population differentiation. The aim of this review and meta-analysis was to verify whether a ketogenic diet without programmed energy restriction generates increases in fat-free mass (FFM) in resistance-trained participants. We evaluated the effect of the ketogenic diet, in conjunction with resistance training, on fat-free mass in trained participants. Boolean algorithms from various databases (PubMed, Scopus. and Web of Science) were used, and a total of five studies were located that related to both ketogenic diets and resistance-trained participants. In all, 111 athletes or resistance-trained participants (87 male and 24 female) were evaluated in the studies analyzed. We found no significant differences between groups in the FFM variables, and more research is needed to perform studies with similar ketogenic diets and control diet interventions. Ketogenic diets, taking into account the possible side effects, can be an alternative for increasing muscle mass as long as energy surplus is generated; however, their application for eight weeks or more without interruption does not seem to be the best option due to the satiety and lack of adherence generated.

Effects of resistance training combined with a ketogenic diet on body composition: a systematic review and meta-analysis

We evaluated the effects of ketogenic diets (KDs) on body mass (BM), fat mass (FM), fat-free mass (FFM), body mass index (BMI), and body fat percentage (BFP) compared to non-KDs in individuals performing resistance training (RT). Online electronic databases including PubMed, the Cochrane Library, Web of Science, Embase, SCOPUS, and Ovid were searched to identify initial studies until February 2021. Data were pooled using both fixed and random-effects methods and were expressed as weighted mean difference (WMD) and 95% confidence intervals (CI). Out of 1372 studies, 13 randomized controlled trials (RCTs) that enrolled 244 volunteers were included. The pooled results demonstrated that KDs significantly decreased BM [(WMD = -3.67 kg; 95% CI: -4.44, -2.90, p < 0.001)], FM [(WMD = -2.21 kg; 95% CI: -3.09, -1.34, p < 0.001)], FFM [(WMD = -1.26 kg; 95% CI: -1.82, -0.70, p < 0.001)], BMI [(WMD = -1.37 kg.m^-2; 95% CI: -2.14, -0.59, p = 0.022)], and BFP [(WMD = -2.27%; 95% CI: -3.63, -0.90, p = 0.001)] compared to non-KDs. We observed beneficial effects of KDs compared to non-KDs on BM and body fat (both FM and BFP) in individuals performing RT. However, adherence to KDs may have a negative effect on FFM, which is not ameliorated by the addition of RT.