Obesity is a common chronic disease characterized by the excessive accumulation or abnormal distribution of fat, which poses significant health risks and requires ongoing management (1). According to the World Health Organization, adults are considered overweight if they have a body mass index (BMI) of 25 kg/m² or higher, and as obese if their BMI is 30 kg/m² or more. For children, age must be taken into account when defining overweight and obesity (2). The pathogenesis of obesity is complex, involving biological, psychosocial (3, 4), genetic (5), and socio-economic (1) factors, as well as diverse pathways and mechanisms that contribute to adverse health outcomes (6). Obesity is closely linked to an increased risk of several chronic diseases, including cardiovascular disease (6), type 2 diabetes (7), various cancers (8), osteoarthritis (9) and several other diseases, and it poses serious public health challenges. Over the past decades, the global obesity pandemic has intensified significantly. From 1990 to 2022, the prevalence of obesity more than doubled worldwide. In 2022, 2.5 billion adults aged 18 and older were classified as overweight, including over 890 million who were obese (2). Given these alarming trends, obesity continues to be a major global public health challenge that requires urgent attention and intervention.

The term “circadian” refers to processes that follow a roughly 24 h cycle (10). Circadian rhythms are endogenous regulators in cells or organisms that coordinate physiological and behavioral activities, playing a vital role in numerous physiological processes (11). These rhythms are controlled by the central clock, located in the suprachiasmatic nucleus (SCN) of the hypothalamus, as well as the peripheral clocks throughout the whole body (12). Extensive studies have provided insights into the mechanism by which circadian rhythms contribute to obesity, involving the interaction of various physiological, environmental, and genetic factors (13). The circadian rhythm system regulates various metabolic processes related to obesity, including glucose and cholesterol metabolism (14, 15). In glucose metabolism, sleep deprivation reduces brain glucose utilization, resulting in increased glucose concentrations in peripheral tissues. This elevation may promote the development of insulin resistance and lead to obesity (16). Researchers have found that day and night reverse feeding aggravates the rise in blood glucose and lipid levels caused by a high-fat diet in 8–10-week-old mice. Notably, daytime feeding results in a more obvious increase in weight gain, fasting blood glucose concentration, and lipid concentration (17). Similarly, the plasma levels of hormones involved in metabolic processes, such as glucagon and leptin, also follow circadian rhythms (18, 19). Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) enhance insulin secretion and inhibit food intake to control glucose homeostasis. Under similar dietary conditions, plasma concentrations of glucagon, GLP-1 and GIP were found to be higher in the daytime than at night, while the levels of GLP-1 and GIP were lower at night, which may be the reason for the frequent increase of food intake at night, thereby increasing the risk of obesity (18). Leptin, an essential pleiotropic adipokine, plays a key role in regulating energy balance (20). A study showed participants with short sleep duration reduced leptin levels, increased auxin-releasing peptides, and heightened hunger and appetite, all of which can lead to obesity (21, 22). Additionally, the environment and the resulting circadian rhythm disorders are also closely related to obesity. An unnatural distribution of light and dark within 24 h can interfere with the early development of the nervous system of mice and change the weight regulation during the early growth. The reintroduction of fragmented day-night cycles in adulthood has also been led to overeating in adulthood (23). Research on the role of circadian rhythm genes in obesity has begun very early and continues to develop. As early as 2005, Turek FW found that Clock mutant mice fed a high-fat diet became obese at a young age and exhibited several metabolic and endocrine abnormalities consistent with metabolic syndrome such as increased appetite, obesity, hyperleptinemia, hyperlipidemia, hyperglycemia (24). Since then, research on the relationship between obesity and circadian rhythms has continued to advance. A recent study revealed, for the first time, the correlation between the methylation of circadian rhythm genes BMAL1 and Clock and various obesity-related indices, including body mass index, waist circumference, fasting blood glucose, total cholesterol, low density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, HOMA-IR, leptin, adiponectin and resistin. This study opens up possibilities for exploring the epigenetic mechanisms by which circadian rhythm regulation influences obesity (25).

The systematic review is a structured process of collecting, screening, evaluating, and analyzing all relevant literature on a specific question or research topic. It encompasses both qualitative and quantitative reviews, aiming to provide an unbiased synthesis of studies, identify contradictions, gaps, and inconsistencies in the evidence, and explore their underlying causes. Ultimately, it seeks to propose new theories or critically assess existing ones. Different from systematic reviews, bibliometrics is the study of academic publishing that uses mathematical and statistical methods to analyze publishing trends and highlight relationships between published works (26). Based on the complexity and quantity of available information, this approach can intuitively visualize countries, institutions, authors, journals, literatures and keywords, allowing researchers to quickly gain a deep understanding of the thematic evolution, research hotspots, and emerging trends within specific fields (27). However, no bibliometric study has been conducted on the relationship between obesity and circadian rhythm. Thus, in this study, we employed bibliometric methodologies to assess the research status and current focus of studies on circadian rhythm in obesity, and to explore potential directions for future research.

Using VOSviewer, CiteSpace, and WPS, 2,870 publications from Web of Science were analyzed. Despite some fluctuations over the past 50 years, the results showed an overall rising trend in both the quantity of publications and annual co-citations. Notably, there has been a significant increase since 2013, reflecting growing interest among researchers in the connection between circadian rhythm and obesity.

The primary countries and regions contributing to research in circadian rhythm and obesity were the USA, Europe, and Asia. The USA held a leading position, with a significantly higher number of publications, citations, H-index, and Total Link Strength (TLS) compared to other countries, driving forward research in this field. Among the top 11 institutions with the highest number of publications, 7 institutions are located in the USA, while the remaining four institutions are in France or Spain, further illustrating the prominent role of the USA in this field. As shown in Table 3, the University of California System leads in the number of publications from the USA, conducting extensive research on the circadian rhythm in obesity. Recently, clinical trials demonstrated that 12 weeks of TRF within a self-selected 10 h eating window can significantly improve cardiac metabolic outcomes, including reductions in body weight, body mass index, waist circumference, glucose levels, and systolic blood pressure. They also emphasized the importance of studying the mechanisms of TRF, particularly its impact on circadian rhythm disorders (41). The significance of nodes in the network can be measured using centrality, a parameter where higher centrality means more frequent cooperation between countries or regions (42). In terms of centrality rankings, 7 institutions belong to the United States, the other institutions, respectively, locate in France, Spain, and Germany. China and Japan ranked second and third in terms of the quantity of papers published, but TLS was relatively low. Thus, it is recommended to enhance cooperation between countries and institutions to publish more influential articles and jointly advance the field of circadian rhythm research in obesity.

In terms of authorship, Garaulet, Marta ranked first among the top 10 authors with the most publications, followed by Oster, Henrik and Panda, Satchidananda. Garaulet, Marta reviewed scientific evidence showing the relationship between chronobiology and obesity, and concluded that chronobiology could be a valuable tool for the future treatment of obesity and metabolic syndrome through chronotherapy (43). Garaulet, Marta pointed out that the circadian rhythm health status of obese, overweight, and normal-weight children differs according to the assessment of a global circadian score (GCS), with children with obesity showing poorer circadian cycle health (44). Additionally, Turek FW was the most co-cited researcher, and his academic interest mainly focused on neurobiology, sleep, circadian rhythm, metabolism and gut microbiota. Through the observation of a genetic mouse model of obesity and diabetes (db/db mouse), he found that impaired leptin signaling has harmful effects on the regulation of sleep volume, sleep structure and time consolidation of wake states, leading to a decrease in circadian rhythms of activity (45).

The journal with the most publications in this field was Proceedings of the National Academy of Sciences of the United States of America, followed by Science. The American Journal of Physiology was the most frequently cited journal. The top ten journals with the most publications and the top thirteen journals with the highest centrality all belong to the JCR partitions of Q1 or Q2, indicating that researchers can prioritize these types of journals when publishing articles, as the publications involved in this analysis are of a dependable standard.

The co-cited references are considered foundational to research in a certain field, and the development of keywords can reflect the evolution of frontier knowledge. Both co-cited references and keywords play a crucial role in guiding future study directions in this field (46). In this study’s analysis, similar topics emerged in co-cited reference clustering and keyword clustering, suggesting that these topics represent popular research areas in this field. The gene expression of obesity was identified as an early hotspot in circadian rhythms and obesity studies, which may be related to the successful isolation of obese gene in rats and humans and the discovery of human obese gene structure (47, 48). In 1994, Joseph S Takahashi and his research group defined the CLOCK gene, which is essential for normal circadian rhythm behavior, proposing that the Clock gene product may be part of the circadian clock mechanism (49). Since then, scientists have gradually focused on the clock gene expression of obesity. At the molecular and cellular levels, the biological clock in adipose tissue is based on the interlocking transcription-translation feedback loop of clock genes and proteins. The expression patterns of clock genes such as BMAL1 and CLOCK show 24 h oscillations in adipose tissue (50). Driven by the CLOCK and brain and muscle ARNT-Like 1 gene (BMAL1) transcription factor dimers (51, 52), the molecular clock regulates the expression of thousands of genes, including period (PER) genes (PER1, PER2 and/or PER3) and cryptochrome (CRY) genes (CRY1 and CRY2) (53). When organisms are exposed to circadian rhythm disruptors, many biological systems and feedback loops, designed to predict and regulate circadian homeostasis, may become misaligned. Over time, this imbalance can negatively impact organs and tissues, disrupting catabolism and anabolic processes and leading to obesity (54). According to the timeline representing the evolution of clusters, endothelial nitric oxide synthase (eNOS) has been a research hotspot in recent years. Evidence suggests that eNOS signaling transduction is impaired in mice experiencing both obesity and constant darkness, although eNOS expression remains unchanged (55). However, the involvement of eNOS in circadian rhythm regulation remains unclear, and further research is needed to elucidate the role of eNOS in the fat clock (56).

With the research progress on circadian rhythm in obesity, several emerging fields have attracted increasing attention from researchers. One notable area is intermittent fasting. As obesity becomes an important public health issue, it has gained popularity in recent years as an approach to controlling obesity and weight loss (57). This may be attributed to the fact that intermittent fasting is an easier strategy for most people than increasing energy consumption through physical exercise (58). Intermittent fasting focuses on limiting eating to specific times within a day or week. This dietary intervention is similar to calorie restriction and typically includes two main types: alternative day fasting and TRF (59). A number of studies have shown that intermittent fasting can reduce body weight and fat by improving insulin resistance, lowering total cholesterol, low-density lipoprotein (LDL), triglycerides, and simultaneously elevating high-density lipoprotein (HDL) levels (60–62). TRF, a common form of intermittent fasting, involves limiting food intake to a specific time window—usually between 1 and 12 h—and avoiding calorie consumption for the rest of the day (63). Clinical trials have shown that TRF can change the expression of clock genes, restore the circadian rhythm of metabolites and glucose-regulated hormones, and establish the 24 h gene expression spectrum that regulates transcriptional control in human adipose tissue (64). Chambers et al. (65) critically evaluated the studies from PubMed and concluded that early circadian-aligned TRF diets are linked to increased diet-induced thermogenesis, improved blood glucose control, and weight loss. These findings suggest that circadian-aligned TRF diets may be an effective strategy for enhancing metabolic health and promoting weight loss in individuals who are overweight or obese.

Recently, the effects of TRF on the gut microbiome and body weight has gained attention. A study by Thaiss et al. revealed that the composition and function of the intestinal flora in laboratory mice fluctuated within a few hours, aligning with the 24 h rhythmic hypothesis of intestinal microbial function. It is proved that the rhythm of host biological clock-driven functions, such as the timing of food intake, is crucial to the daily oscillations that shape the composition of the microbiota (66). In multiple human and experimental models, melatonin has shown to improve gut microbiota imbalance related to metabolic status by regulating disrupted circadian rhythms, thus demonstrating beneficial effects on obesity (67, 68). Additionally, a preliminary randomized, double-blind, placebo-controlled study conducted on overweight and obese individuals with insulin resistance revealed that supplementation with live or pasteurized myxobacteria for 3 months increased insulin sensitivity and reduced insulinemia and total plasma cholesterol. Moreover, there was a slight reduction in fat mass and hip circumference compared to baseline (69). Therefore, in clinical practice, microbiome-targeted therapies could emerge as novel treatment options for obesity and metabolic syndrome (70).

The study of circadian rhythms and obesity may also have an important impact on clinical practice and public health policies. Through in-depth understanding of the relationship between circadian rhythm and obesity, a more personalized treatment plan can be developed from multiple perspectives such as diet, sleep, and gut microbiome to improve the therapeutic effect (44, 54, 71). Obesity is a major public health concern, and we believe it is important to strengthen interdisciplinary cooperation among medicine, nutrition, psychology, and other disciplines to inform the formulation of scientific public health policies. Shift work refers to the working mode of periodically changing working hours (72). It can disturb the circadian rhythm, leading shift workers to face a variety of health issues (73, 74). Numerous studies have shown that shift work may be associated with an increased risk of overweight and obesity (75–77). Therefore, shift schedules should be created according to recommended ergonomic standards to mitigate adverse health impacts by preventing or minimizing circadian rhythm disorders and insufficient sleep (78). Based on the research results of circadian rhythm and obesity, more scientific public health policies can be formulated, such as promoting healthy lifestyles, providing scientific dietary and exercise guidance, and raising public awareness of circadian rhythms. The WHO’s recent recommendations on obesity mention that in order to prevent childhood obesity, children should follow a healthy lifestyle and ensure sleep time and quality (79), indicating that the role of circadian rhythms in obesity is gradually being valued. Therefore, we recommend that more parts of the impact of circadian rhythms on obesity should be added to the guidelines issued by relevant international organizations in the future, helping people understand and maintain a healthy biological clock as a strategy for the prevention and treatment of obesity, thereby reducing its prevalence.

This study conducted a bibliometric analysis of the circadian rhythm in obesity, using Citespace and VOSviewer to comprehensively analyze and visualize the literature network. We summarized the current research landscape and identified key research forces in this field, and predicted future trends. However, due to the limitations of bibliometric tools, paper types and language, valuable newly published research results may have been overlooked, and important papers published in languages other than English may be missed. Our study was restricted to publications in the WoSCC database, as CiteSpace currently cannot analyze references from other databases. Future software improvements are expected to broaden the range of database selection for analysis. In addition, as the circadian rhythm in obesity is a developing research field, some recently published high-quality articles may be cited less frequently due to their short publication time, which may lead to differences between research results and actual situations.

In this study, we utilized the Web of Science database, along with CiteSpace and VOSviewer software, to conduct bibliometric and visual analysis of research on obesity and circadian rhythm. This approach provided a scientific and intuitive view of the overall research landscape in this field. According to bibliometric analysis, research on the circadian rhythm of obesity began in 1963, and the number of published articles has significantly increased over the past few decades. We conducted an in-depth analysis of publication data, covering various aspects such as the quantity of published articles, prominent countries and institutions, influential authors and co-cited authors, journals published, and cooperative networks. Furthermore, the study highlighted major research hotspots, development trends, and frontier topics related to obesity and circadian rhythm. As the understanding of the circadian rhythm mechanism deepens, the therapeutic targets related to circadian rhythms present promising prospects for obesity treatment. The investigation of obesity mechanisms and treatment methods that leverage circadian rhythm has emerged as a major research hotspot. Key areas of focus include circadian gene expression, intermittent fasting, restricted feeding, endothelial nitric oxide synthase, and gut microbiota. These fields highlight potential future research directions and offer valuable guidance for advancing studies in this field.

To sum up, our results may offer valuable insights for researchers to understand the current status and emerging trends in circadian rhythm research related to obesity. This analysis can serve as a reference and provide suggestions for guiding future research directions in this field.