Introduction

Obesity is a complex, multifactorial, chronic disease in which excess adipose tissue or accumulation of dysfunctional adipose tissue has negative health consequences, increasing the risk of long-term medical complications by its association with multiple diseases. Also, obesity leads to impaired quality of life and reduced life expectancy [1]. Epidemiological studies define obesity by calculating the body mass index (BMI: weight divided by the square of height in meters), which allows stratifying obesity-related health risks at a population level. Operationally, it is diagnosed in patients with a body mass index equal to or greater than 30 kilograms per square meter and is subclassified into class one (equal to or greater than 30 to 34.9 kilograms per square meter), class two (equal to or greater than 35 to 39.9 kilograms per square meter) and class three (equal to or greater than 40 kilograms per square meter). At a population level, health complications from excess body fat increase as the body mass index increases [2]. At an individual level, complications are caused by a complex interaction between excess adiposity, its location and distribution, and many other factors, such as environmental, genetic, biological, and socioeconomic factors [3] (Table 1).

During the last three decades, the prevalence of obesity has steadily increased worldwide [1,2]. Currently, Chile leads the world rankings of obesity, presenting one of the highest prevalences [4]. According to data from the latest National Health Survey (2016 and 2017), the population over 15 years of age with obesity reached 34.4%, while overweight reached 40%. On the other hand, the prevalence of overweight has increased by 6% since the 1980s [5], up to 74.2% according to data from the latest National Health Survey [6].

Following the sustained increase in the prevalence of obesity in our country and its adverse effects on health, in July 2021, Resolution Project No. 1365 was unanimously approved. This resolution requests the President of the Republic to "recognize obesity as a chronic disease whose prevention, diagnosis, treatment, and follow-up should receive financial coverage by the State and Social Security Health Institutions, facilitating the population’s access to adequate healthcare (consultations, examinations, drugs and supplies, surgical procedures, bed days, and controls)" [7]. The unanimous approval of this resolution demonstrates the recognition of obesity as a profound public health problem that must receive effective and timely treatment. The importance of obesity as a public health problem is demonstrated not only by its negative impact on physical and psychological health [8] but also by the significant increase in healthcare costs [9,10]. Additionally, people with obesity experience widespread weight prejudice and stigma, contributing to increased morbidity and mortality regardless of weight or body mass index [11].

Obesity is caused by the complex interaction of multiple genetic, metabolic, behavioral, and environmental factors. However, the latter two factors are believed to be the leading cause of the considerable increase in its prevalence [12,13]. During the last decades, a better understanding of its complex etiopathogenesis and biological underpinnings has been achieved [13]. Regarding the genetics of obesity, genome-wide association studies in large epidemiological cohorts have identified more than 140 regions of the genome that influence body mass index. In turn, those possessing significant association with excess weight are the intronic regions of the FTO gene [14]. Studies with monozygotic and dizygotic twins have shown a relatively high degree of heritability and support evidence of heritability of body weight and eating behavior [15,16].

The brain plays a crucial role in energy homeostasis by regulating food intake and caloric expenditure [17]. Decreased food intake and increased physical activity lead to a negative energy balance and trigger adaptive metabolic and neurohormonal mechanisms [18,19]. Targeted therapies to treat these alterations of neurohormonal mechanisms may become effective tools for the long-term treatment of obesity [20] (Table 2).

Approach to obesity

New approaches have been proposed to diagnose and evaluate people living with obesity in clinical practice [3,12,13,21]. Although body mass index is widely used to assess and classify obesity, it is not an accurate screening tool for adiposity-related complications [13]. Waist circumference has been independently associated with increased cardiovascular risk but is not a good predictor of visceral adipose tissue individually [22]. Integrating body mass index and waist circumference into the clinical assessment may identify the higher risk phenotype of obesity better than each of these parameters alone, especially in those individuals with a lower body mass index [23,24]. In addition to body mass index and waist circumference measurements, a complete medical history to identify the causes of obesity, an adequate physical examination, and relevant laboratory tests will help identify individuals who will benefit from different obesity treatments [25].

In Canada, for example, the Edmonton Obesity Staging System (EOSS) has been proposed to guide clinical decisions based on the assessment of people living with obesity independently from body mass index [21,26]. This five-stage staging system considers metabolic, physical, and psychological parameters to determine optimal obesity treatment. Population-based studies have shown this scale to be a better predictor of all-cause mortality compared with body mass index or waist circumference measurements alone [27,28]. However, there are still no studies validating this system in the Chilean population.

Obesity treatments should aim at improving health and well-being, not only at losing body weight [28,29]. Multiple studies show that modest weight losses, between 3% and 5% of total weight [30,31,32,33], may be sufficient to improve metabolic parameters in patients living with overweight or obesity. In a pilot lifestyle intervention program among overweight or obese adults at risk for Type 2 diabetes, an approximate 4% weight reduction after four months of intervention achieved significant improvement in fasting glycemia, basal insulinemia, cholesterol, and blood pressure [34]. However, it is now recognized that the treatment approach should be comprehensive and not solely focused on weight. Since the existing literature is mainly based on weight loss outcomes, several recommendations in this guideline focus on this. However, further research is needed to shift the therapeutic focus toward improving health outcomes centered on the patient and their quality of life and not solely on weight loss.

The dominant cultural narrative regarding obesity fuels assumptions about personal irresponsibility, lack of willpower, guilt, and shame [35]. Notably, the stigma of obesity negatively influences the level and quality of care people receive [36].

Due to the above, we propose using an approach strategy based on five steps to systematize and cover each component of the patient’s history and context to recommend the most suitable treatment.

Step 1: recognizing obesity as a chronic disease and obtaining patient permission

Healthcare professionals should recognize and treat obesity as a chronic disease caused by abnormal or excessive accumulation of body fat (adiposity), which impairs health and is associated with an increased risk of morbidity and premature mortality [1,2,12,37,38,39]. This disease does not present in the same way in all patients and requires individualized treatment and long-term support, just like any other complex chronic disease.

Body weight bias in healthcare can reduce the quality of care for people with obesity [36]. One of the keys to reducing weight-related bias, stigma, and discrimination in healthcare settings is for healthcare professionals to be aware of their own attitudes and behaviors toward people living with obesity [40].

Healthcare professionals should not assume that all patients are ready to initiate obesity treatment. To assess this, they should ask the patient’s permission to discuss obesity and, if obtained, can begin to discuss relevant assessment and treatment possibilities [41,42].

Step 2: Assessment

A holistic approach focused on healthy behaviors should be promoted, and the underlying causes of weight gain should be addressed, avoiding stigmatizing and overly simplistic narratives.

Direct measurement of height, weight, waist circumference, and calculation of body mass index should be included in the routine physical examination of all adults. Although the body mass index has its limitations, it remains a valuable tool for screening purposes and assessing population health [43]. For individuals with a high body mass index (25 to 34.9 kilograms per square meter), waist circumference should be measured regularly to identify individuals with increased visceral adiposity and related health risks [44].

The root causes of obesity include biological factors such as genetics, epigenetics, neurohormonal mechanisms, associated chronic diseases, and medications that cause increased adipose tissue and body weight; sociocultural practices and beliefs; social determinants of health; the built environment, individual life experiences such as adverse childhood experiences; and psychological factors such as mood, anxiety, binge eating disorder, attention-deficit/hyperactivity disorder, self-esteem, and identity [41]. Working with individuals to understand their context and culture, and integrating their causes, allows the development of personalized intervention plans. These plans can be integrated into long-term therapeutic relationships for follow-up of obesity and related comorbidities, including addressing the causes of obesity. A complete medical history is recommended to identify these causes and physical, mental, and psychosocial barriers to possible treatments. Physical examination, laboratory, imaging, and other investigations should be performed according to clinical judgment. We also recommend measuring blood pressure in both arms and obtaining fasting glycemia or glycosylated hemoglobin values, a lipid panel to determine cardiometabolic risk, and, when indicated, transaminase levels in conjunction with abdominal ultrasound to detect nonalcoholic fatty liver disease.

Step 3: Discussion of treatment options

People living with obesity should receive individualized care plans that address the root causes and support behavioral change (e.g., nutrition, physical activity) and complementary therapies, which may include psychological, pharmacological, and surgical interventions.

Guideline development

Scope

The target audience for this guide is health professionals (mainly those working in primary care), people living with obesity, and their families. This guide can also be used by policy-makers, legislators, or decision-makers involved in managing and administering resources for obesity care. This guideline focuses on adult obesity and is intended to be an up-to-date document on inter- and multidisciplinary management, free of stigmatization, including effective and safe treatments according to the available evidence. The clinical recommendations are used as a guide for healthcare professionals. Resource limitations and individual patient preferences may make it challenging to implement all the recommendations, but this guide aims to improve the standard and access to care for people with obesity in all regions of Chile.

Methodology

The Canadian clinical practice guideline for adult obesity was developed by Obesity Canada and the Canadian Association of Bariatric Physicians and Surgeons and published in August 2020. Given the extensive resources used to develop a clinical practice guideline and the high level of interest in some countries, Obesity Canada developed a pilot project designed to adapt and implement the guideline to local contexts in other countries.

Composition of the group participating in the development of the guideline

In Chile, the project was awarded, after a formal application, to the Chilean Society of Bariatric and Metabolic Surgery. Dr. Yudith Preiss Contreras, a specialist in Clinical Nutrition of Adults, and a member of the Chilean Society of Bariatric and Metabolic Surgery, was in charge of the project’s development. In addition, technical guidance was provided by Dr. Ximena Ramos Salas, Director of Research and Policy at Obesity Canada, who coordinated the development of the guide in Canada, and Miguel Alejandro Saquimux Contreras, research assistant at Obesity Canada.

The Chilean Society of Bariatric and Metabolic Surgery established an Executive Committee made up of four participants: the President and former President of the Chilean Society of Bariatric and Metabolic Surgery, two specialists in the medical and surgical management of obesity, a physician specializing in clinical nutrition of adults, and a bariatric surgeon who also served as secretary of the Chilean Society of Bariatric and Metabolic Surgery: Francisco Pacheco Bastidas, Claudio Canales Ferrada, Yudith Preiss Contreras, and Rodrigo Muñoz Claro, respectively. An Intersocietal Committee was formed to involve the largest number of professionals, scientists, and academics related to the study and management of obesity in our country. This committee included the Chilean Association of Clinical Nutrition, Obesity and Metabolism, the Chilean Society of Family Medicine, the Chilean Society of Neurology, Psychiatry and Neurosurgery, the Chilean Society of Nutrition, the Chilean Society of Sleep Medicine, and the Chilean Society of Gynecology and Obstetrics, whose representatives participated in both the Extended Executive Committee, serving as lead authors of chapters, and/or as external reviewers.

The selection of authors included representatives of the public and private health networks. The number of participating authors per chapter ranged from two to five. In addition, methodological experts were involved in updating the evidence and adapting the guidelines. The entire team of authors, steering committee, independent methodologists, and administrative staff supported the project’s coordination and development. The methodology chapter summarizes the guideline development process and the responsibilities of each participating group.

This process did not involve patients because, in this first stage, it was not possible to implement an administrative structure capable of making an open and transparent call for organizations and/or interested individuals to participate in a meaningful way (availability of time for weekly meetings, full professional competence in English, participation in representative non-governmental organizations, among other criteria). In the future, we hope that we will have the capacity to convene individuals and patient organizations, ensuring an active involvement that reflects their capabilities and contributions when updating this guideline.

Representatives of indigenous peoples did not participate in the project because, in Canada, the specific chapter on indigenous peoples resulted from a research process investigating the perceptions and actions on obesity among these people. This could not be done at this point in the project. The Executive Committee intends to include in a future update a chapter that responds to the realities of the indigenous peoples living in Chile. For the development of this adaptation, the GRADE framework for the adoption, adaptation, and de novo development of reliable recommendations, known as GRADE-ADOLOPMENT [62], was used as a basis for the guideline developed by Obesity Canada [26]. First, each panel of authors evaluated the recommendations of the original guideline, identifying which recommendations could be adopted after considering all the criteria in the GRADE-EtD framework and evaluating the judgments that led to the final formulation of the original recommendations. Out of 80 original recommendations, 76 were considered for adoption, with no modifications required.

Only one original recommendation was adapted, identifying sufficient judgments to change the strength and direction of the original recommendation.

The final adopted recommendations and adapted recommendations can be seen in Tables 2 and 4, respectively. The complete description of the methodology used can be found in the Methodology chapter of the Chilean Obesity Guidelines.

Secondly, the executive committee carried out a prioritization process of de novo clinical questions considered vital and indispensable for the Chilean guideline and not addressed in the guideline developed for Canada. The Chilean authors submitted 41 potential questions for new recommendations. The panel members finally identified and selected 12 questions to develop de novo recommendations. Therefore, a new search, selection, and synthesis of the evidence were performed.

Literature review and assessment of the certainty of the evidence

Systematic reviews were searched on the L-OVE (Living OVerview of Evidence, available at www.iloveevidence.com) platform. This system maps and organizes evidence by health topics, continuously updating the evidence through a central repository called the Epistemonikos database (available at https://www.epistemonikos.org) [63]. This database regularly searches 10 information sources: Cochrane Database of Systematic Reviews, Pubmed/MEDLINE, EMBASE, CINAHL, PsycINFO, LILACS, DARE, Campbell Library, JBI Database of Systematic Reviews and Implementation Reports, and EPPI-Centre Evidence Library. Additionally, a search for randomized clinical trials not included in systematic reviews was performed through the Pubmed/MEDLINE database. Two reviewers screened, selected, and extracted data from the included studies for each new guideline question. Subsequently, evidence profiles were created using the summaries of findings tables (Summary of Findings), assessing the evidence’s certainty. To formulate the final recommendations, the EtDframework was completed [64] using iEtD software to help the panel document and follow the recommendation process [65]. In a face-to-face meeting in November 2021, the Epistemonikos team trained the authors in using the platform.

An iterative process was carried out among the panel members, involving the leaders and authors of the different chapters. For each of the 12 recommendations, the methodological team of the Epistemonikos Foundation performed the evidence profiles and the evaluation of their quality. The GRADE-EtD framework [62] was used for the clinical recommendations, allowing for a structured consensus process and transparent documentation of all participant judgments.

Chapter leaders and participants voted on each new question to ensure consensus by evaluating the evidence supporting each question. The certainty of the evidence was assessed using the GRADE approach, which defines certainty as the degree of confidence that the estimate of an effect is adequate to support a given decision or recommendation [66]. This is classified as "high," "moderate," "low," or "very low" depending on the evidence available for each guideline question. The strength of a recommendation can be strong, or conditional (also known as weak). Understanding this interpretation is essential for decision-making [67].

For the final wording of the recommendations, the panel made a consensus of judgments that allowed the strength and direction of each recommendation to be determined, reflecting the degree of confidence held about the desirable or undesirable effects of each intervention. The recommendations were categorized as strong or weak according to the certainty of the evidence and the effect they have on important outcomes. The steering committee, chapter leaders, and authors formulated the recommendations based on the highest level of evidence available (Table 3).

Only one original recommendation was adapted, identifying local evidence linked to the cost and accessibility of the intervention sufficient to change the original recommendation’s strength and direction, maintaining the evidence’s level of certainty but decreasing the strength of the recommendation (Table 4).

The new recommendations, along with the adapted recommendation, are described in Table 4. A full description of the evidence supporting the final recommendations can be found as supplementary material in "Summary and Synthesis of Evidence." These recommendations were not reviewed or approved by the original Canadian guideline committee.

Dissemination and implementation

This guideline is intended to remain a living document that is constantly updated and allows patients, professionals, and health policy decision-makers to have a tool based on the best available evidence to define support mechanisms for prevention and cost-effective and safe treatments. For this purpose, an independent web page (www.guiasobesidadchile.com) was developed as a repository of the chapters in extenso, the recommendations, and the methodology. In the near future, it will include videos, webinars, and educational material for patients living with obesity.

The implementation of this guide will depend on the reception of health authorities, the allocation of resources for the training of health professionals, and calls to action from patient and family organizations.

Conclusions

Obesity is a chronic, multifactorial, progressive, and relapsing disease. People living with obesity often suffer from stigmatization and blame, increasing the access gap and worsening health outcomes. This paper demonstrates advances in understanding the pathophysiology, health determinants, assessment, and treatment of obesity. It also seeks to redirect the multidisciplinary management approach toward stigma-free care and to focus outcomes on patient quality of life rather than solely on weight loss.