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

Abstract

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.

Keywords: BIA; BIVA; Keto diet; Phase angle; Very low-carbohydrate ketogenic diet.

Fig. 1

Main body mass components at molecular, cellular, tissue, and whole-body level of body composition. * = Formed by all cells involved in metabolic processes, including the protoplasm in fat cells; FFM= fat-free mass; LBM= lean body mass; LM= lean mass; ALM= Appendicular lean mass; ICW= Intracellular water; ECW= Extracellular water; NMA= nonmetabolically active; IAT= Internal adipose tissue formed by visceral and non-visceral adipose tissue; SAT= Subcutaneous adipose tissue

Fig. 2

Key events in the history of bioelectrical impedance analysis (BIA). FM: fat mass; FFM: fat-free mass; 4C: four-component model; DXA: dual-energy X-ray absorptiometry; BIVA: bioelectrical impedance vector analysis; ICW: intracellular water; ECW: extracellular water; SMM: skeletal muscle mass

Fig. 3

PRISMA flow chart for the search strategy

Fig. 4

Number of bioimpedance technologies used in the selected studies (N = 72)

Fig. 5

Pie chart illustrating the number of predicted body composition variables and their respective percentages in relation to the total predictions (N = 192) across the selected studies (N = 72)

Fig. 6

Best practices for studies using BIA