To better understand the underlying causes of individual variability in weight maintenance after intentional weight loss, the United States’ National Institutes of Health requested applications for mechanistic clinical trials that enable discovery science approaches to elucidate behavioral, psychosocial, and physiological mechanisms underlying the variability in weight regain using measures acquired before and after a behavioral intervention that induces weight loss. The multidisciplinary consortium, Physiology of the Weight Reduced State (POWERS), was funded to address this need. After an Introduction to this Special Issue, the articles describe the POWERS study design and the rationale behind the design. Each manuscript focuses on factors hypothesized to account for variability in weight change after intentional weight loss. The special issue includes a manuscript that provides a study overview, including the behavioral intervention used to induce weight loss (Overview and Study Design). We examine behaviors and neurocognitive factors related to eating, and psychological factors related to weight regulation, physical activity and sleep. The measures, the rationale behind them and how the data are collected are described (Design and Rationale for Assessment of Food Intake, Physical Activity and Other Behavioral Constructs). An individual’s social and physical environment, psychological state, and social determinants of health (SDoH) could influence the amount of weight regain after intentional weight loss. We report the measures and rationale for their use (Environmental, Psychological, and Social Determinants of Health). Energy intake and energy expenditure, and the difference between them, are primarily responsible for weight change, so it is critical to assess them to address the study aims. Describing the measures and how they are obtained is in another article in this special issue (Assessing Energy Balance). Several biospecimens are obtained to assess the physiological variability that contributes to mechanisms responsible for variability in weight change after weight loss. The rationale for the selected biospecimens and how they are obtained, are described (Strategies for the Analysis of Biological Specimens). All of the manuscripts were reviewed and approved by the POWERS Publications and Presentations Committee, chaired by Steven H. Belle (Data Coordinating Center, University of Pittsburgh), with members Dympna Gallagher (clinical center at Columbia University Irving Medical Center), Susan B. Roberts (DTP clinical center, Dartmouth College), and Maren Laughlin (National Institute of Diabetes and Digestive and Kidney Diseases of the U.S. National Institutes of Health).

To better understand the underlying causes of individual variability in weight maintenance after intentional weight loss, the United States’ National Institutes of Health requested applications for mechanistic clinical trials that enable discovery science approaches to elucidate behavioral, psychosocial, and physiological mechanisms underlying the variability in weight regain using measures acquired before and after a behavioral intervention that induces weight loss. The multidisciplinary consortium, Physiology of the Weight Reduced State (POWERS), was funded to address this need. After an Introduction to this Special Issue, the articles describe the POWERS study design and the rationale behind the design. Each manuscript focuses on factors hypothesized to account for variability in weight change after intentional weight loss. The special issue includes a manuscript that provides a study overview, including the behavioral intervention used to induce weight loss (Overview and Study Design). We examine behaviors and neurocognitive factors related to eating, and psychological factors related to weight regulation, physical activity and sleep. The measures, the rationale behind them and how the data are collected are described (Design and Rationale for Assessment of Food Intake, Physical Activity and Other Behavioral Constructs). An individual’s social and physical environment, psychological state, and social determinants of health (SDoH) could influence the amount of weight regain after intentional weight loss. We report the measures and rationale for their use (Environmental, Psychological, and Social Determinants of Health). Energy intake and energy expenditure, and the difference between them, are primarily responsible for weight change, so it is critical to assess them to address the study aims. Describing the measures and how they are obtained is in another article in this special issue (Assessing Energy Balance). Several biospecimens are obtained to assess the physiological variability that contributes to mechanisms responsible for variability in weight change after weight loss. The rationale for the selected biospecimens and how they are obtained, are described (Strategies for the Analysis of Biological Specimens). All of the manuscripts were reviewed and approved by the POWERS Publications and Presentations Committee, chaired by Steven H. Belle (Data Coordinating Center, University of Pittsburgh), with members Dympna Gallagher (clinical center at Columbia University Irving Medical Center), Susan B. Roberts (DTP clinical center, Dartmouth College), and Maren Laughlin (National Institute of Diabetes and Digestive and Kidney Diseases of the U.S. National Institutes of Health).

Since last century, major advances in epidemiology, pathophysiology, diagnosis, and management of obesity have been made. The goals of this collection are to discuss these advances from a historical timeline perspective, as well as thoughts for the future of obesity management to include marketing and public health impact.

Drugs for weight loss have been used for a long time in practice, however recent developments prompted the need for this special edition. The goals of this collection are to discuss the current generations of weight loss drugs as it relates to their practical use by clinicians, consideration for future developments by scientists, regulatory framework, economics, and ethics.

The history of IJO's Pediatric Highlights began in 2002 when Associate Editor, Angelo Pietrobelli, remarked that the field of pediatric obesity did not have a journal of its own and inquired whether we thought it was time for such a journal. An analysis of the number and quality of pediatric papers submitted to IJO led to the conclusion that an independent pediatric obesity journal at that time probably would not have sufficient submissions to be successful, however, the seed was planted and a plan was formulated to have a section devoted to papers on pediatric obesity in several IJO issues each year. The Pediatric Highlights section has since flourished with investigators from the pediatric obesity field rewarding IJO by making it a preferred journal for some of their best papers. We now pull these papers into an online collection and look forward to continue serving the field and publishing the very best papers in pediatric obesity each year.

Can we measure food intake in humans? Accurately quantifying food intake is essential to understanding the effect of diet on health and diseases and evaluating the efficacy of dietary interventions. Self-report methods (e.g., food records) remain frequently used despite their evident inaccuracy at assessing energy intake and diet composition. In fact, the many components of food intake: calorie amount, diet composition, eating pattern, meal timing, day-to-day variability, and overall effect on metabolism and energy balance, are excessively difficult to assess in research and in clinical setting. While there are accurate methods to assess sleep and physical activity, there is still a need to develop and validate reliable methods for laboratory and ambulatory measures of many aspects of food intake behavior. The goal of this collection on validated methods to measure food intake in humans, was, in addition to the welcome historical perspectives (Bellisle) (Kissileff), to present current and futuristic methods to measure food intake behavior both in laboratory setting (Bellisle) (Kissileff), (Sazonov) and in ambulatory free-living conditions (Manoogian) (Höchsmann). In a near future, by combining body sensors and remote captors of behavior, validated against state-of-the-art stable isotope methods (Ravelli- Schoeller), with precise quantitative measure of an infinite number of biomarkers (González-Domínguez), we will have a more reliable way to track food intake behavior and its metabolic consequences. However, the technology to support food recognition and portion size estimation is still in its infancy and fully automated precise assessment of food intake in ambulatory setting is not yet a reality. With advance technology and artificial intelligence, we can hope for reduced data analysis-related burden and allow feedback in real-time to users. This will not only help us understand the determinants of this complex behavior but enable targeted dietary interventions to promote health and prevent diseases.

See what readers worldwide have been citing and sharing. In this Web Focus we highlight a selection of articles from 2021, which top the list of the journal’s most cited, downloaded and most shared (including press coverage, blogs, Twitter, Facebook and Weibo). They showcase the breadth of scope and coverage that the journal consistently delivers to its readers.

Research on the pandemic of Covid-19 has demonstrated that there is a higher risk of contracting the disease, increased severity, and poorer outcomes in individuals who are obese.