Effects of low-carbohydrate diets, with and without caloric restriction, on inflammatory markers in adults: a systematic review and meta-analysis of randomized clinical trials

Low-carbohydrate diets (LCDs) have gained interest due to their favorable effects on health outcomes, such as inflammation. However, further research is needed to ascertain the overall effects of LCDs on inflammatory parameters, but at the same time considering weight loss and calorie intake. Thus, a systematic review and meta-analysis of randomized clinical trials was performed to investigate the effects of LCDs compared with low-fat diets (LFDs), with and without caloric restriction, on inflammatory markers in adults. PubMed, Scopus, and Web of Science were searched through March 2022 to select intervention studies addressing LCDs vs. LFDs, in which the following circulating inflammatory markers were used: C-reactive protein (CRP), tumor necrosis factor alpha (TNF-α), and interleukin (IL-6). Analyses were conducted comparing LCDs vs. LFDs through weighted mean differences (WMD) or standardized mean differences (SMD) and 95% confidence intervals (95% CIs) using random effects models. The systematic review and meta-analysis included a total of 51 studies with a total sample of 4,164 adults, with or without other chronic diseases. Intervention durations ranged from 2–144 weeks. LCDs, compared with LFDs, significantly decreased body weight [WMD = −1.35%, p = 0.001], CRP [SMD = −0.1, p = 0.03], and IL-6 [SMD = −0.15, p = 0.09]. However, LCDs did not significantly decrease TNF-α [SMD = −0.02, p = 0.7] compared to LFDs. In conclusion, LCDs have a beneficial effect on markers of inflammation by decreasing CRP and IL-6; this effect has an association with weight loss. However, LCDs were not more effective than LFDs in decreasing TNF-α.