A majority of the articles (11/14, 78.6%) were published in or after 2020 [10, 16,17,18,19,20,21,22,23,24,25]. Three articles were published prior to 2020 (including one in 2009 [26], 2015 [27], 2018 [28]). Details on study characteristics, participants, diet interventions, outcome measures, results, and quality are provided in Tables 1 and 2. Ten of the 14 studies (71.4%) in this review were RCTs [16, 17, 19,20,21,22, 24, 25, 27, 28], 2 (14.3%) were quasi-experimental [10, 23], 1 (7.1%) was a case series [26], and 1 was a cohort study [18]. Two studies utilized a cross-over design [23, 28]. Of the 10 RCTs, 2 used data from the DIRECT trial [16, 17], and 4 were pilot trials [23, 24, 27, 28]. Common limitations of the included articles were small sample sizes, heterogeneity in the study populations, single-center studies, and other potential biases (selection and self-report bias). Study-specific limitations are presented in Table 1.

The sample size of the studies ranged from 10 to 137 participants. Eight articles (57.1%) included only female participants, and these studies focused specifically on breast and gynecologic malignancies [16, 17, 19, 21, 23, 25, 27, 28]. Of the 14 studies, 6 included solely breast malignancies [16, 17, 19,20,21, 27]; 2 included colorectal malignancies [10, 18]; 1 included lung malignancies [22]; 1 included breast and ovarian malignancies [28]; 1 included ovarian, uterine, or cervical malignancies [25]; and 1 included all gynecologic malignancies [23]. Two studies included participants with any malignancy [24, 26]. Even though one RCT did not restrict recruitment based on specific malignancies, it ended up including a majority of participants (90.9%) with breast cancer [24]. Additionally, 93.9% of the participants in this study were female [24]. Cancer staging varied from stage I to stage IV across the studies, and the articles included a range of chemotherapy regimens. These details are presented in Table 1.

This review highlights articles that address a range of dietary patterns. Eight of the 14 studies tested a variation of fasting: 4 studies a short-term fast (STF) [25,26,27,28], 2 an intermittent fast (IF) [18, 20], and 2 a fasting-mimicking diet (FMD) [16, 17]. Besides fasting, 2 studies tested a Mediterranean diet [10, 24]; 1 tested a ketogenic diet [19]; 1 tested a plant-based, high-protein diet [21]; and 1 tested an anti-inflammatory diet [22]. One study simultaneously investigated short-term fasting and a ketogenic diet [23]. Study durations varied and are presented in Table 2.

The studies included in this review (N = 14) all measured chemotherapy toxicities. The most common measurement tool, utilized in eight of the articles, was the National Cancer Institute’s Common Terminology Criteria for Adverse Events (CTCAE) [10, 16, 20, 23,24,25,26,27]. Two articles utilized patient questionaries to document toxicities [18, 23], 2 utilized patient diaries [10, 28], and 1 utilized interviews [28]. Furthermore, two studies analyzed toxicity through the symptom subscales of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire and breast cancer-specific module (EORTC QLQ-C30 and QLQ-BR23) [17, 19].

Fatigue was specifically measured in 3 studies [21, 22, 24]. Two studies measured fatigue through the Brief Fatigue Inventory (BFI) [22, 24]. One study also measured fatigue, sleep problems, and drowsiness on a Symptom Inventory scale rated similarly to BFI [24]. Another study measured fatigue with the Fatigue Symptom Inventory (FSI) and handgrip strength (HGS) [21].

Melnyk and Fineout-Overholt’s hierarchy of evidence for intervention questions was utilized in this review [29]. Ten of the 14 articles in this review are RCTs and were graded as “Level 2” [16, 17, 19,20,