Phase angle as an easy diagnostic tool for the nutritionist in the evaluation of inflammatory changes during the active stage of a very low-calorie ketogenic diet

Int J Obes (Lond). 2022 Sep;46(9):1591-1597. doi: 10.1038/s41366-022-01152-w. Epub 2022 May 25.


Background and aims: Very low-calorie ketogenic diets (VLCKDs) have recently gained increasing interest for their anti-inflammatory effects. Phase angle (PhA), a bioelectrical impedance analysis (BIA)-derived measure used as a screening tool to assess inflammatory status in various clinical conditions has recently been suggested as a novel predictor of inflammatory status in correlation with high-sensitivity C-reactive protein (hs-CRP) levels. PhA's usefulness in monitoring inflammatory status changes in patients with obesity during active phase VLCKD has not yet been explored. The aim of this pilot study was to examine the role of PhA as a biomarker detecting early inflammatory status changes in women with overweight and obesity 1 month into the active stage of a VLCKD.

Methods-results: This uncontrolled, single-center, open-label pilot clinical study investigated 260 consecutively enrolled Caucasian women aged 18-69 years (BMI 25.0-50.9 kg/m2) after 31 days of an active stage VLCKD. Anthropometric measurements and PhA were assessed. hs-CRP levels were determined by nephelometric assay. Dietary compliance, physical activity recommendations, and ketosis status were tested weekly by telephone recall. At Day 31, BMI, WC, and hs-CRP levels were observed to have decreased (∆-7.3 ± 2.9%, ∆-6.3 ± 5.0%, and ∆-38.9 ± 45.6%; respectively), while PhA had increased (∆+8.6 ± 12.5%). Changes in ∆ hs-CRP were significantly correlated with changes in BMI, WC, and PhA (p < 0.001). After adjusting for confounding variables, the correlation between changes in ∆ PhA and ∆ hs-CRP remained statistically significant, albeit attenuated (p = 0.024).

Conclusion: This is the first study reporting how, along with the expected rapid effect on body weight, PhA changes during active stage VLKCD occurred very early on and independently of weight loss, and were negatively associated with hs-CRP levels. These findings further support the VLCKD as a first-line dietary intervention to obtain a rapid effect on the obesity-related inflammatory status. They also suggest the possible role of PhA as an easy diagnostic tool to detect inflammation, thereby avoiding blood sampling and expensive biochemical assays. It is also posited that changes in PhA could help nutritionists correctly plan the different stages of the VLCKD protocol.

Publication types

  • Clinical Study

MeSH terms

  • C-Reactive Protein
  • Diet, Ketogenic*
  • Female
  • Humans
  • Nutritionists*
  • Obesity
  • Pilot Projects


  • C-Reactive Protein