Christopher D. Gardner’s research while affiliated with Palo Alto University and other places

Objective The objective of this study was to identify pretreatment predictors of weight loss in a 12‐month behavioral obesity treatment that restricted either fat or carbohydrates. Methods Participants were 436 adults with overweight or obesity from the Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) trial. Signal detection analysis was used to identify which combinations of 51 pretreatment demographic, clinical, behavioral, and psychosocial variables, along with diet type (healthy low‐fat vs. healthy low‐carbohydrate), formed subgroups that varied in proportion of those achieving at least 5% weight loss at 12 months. Results Overall, 51% of participants achieved at least 5% weight loss at 12 months, with eight subgroups identified through signal detection. Diet type was not a key factor. Among racial and ethnic minority participants, the best predictors of weight loss were lower levels of emotional eating, less friend discouragement, and presence of metabolic syndrome. Among non‐Hispanic White participants, the best predictors were high confidence in participating fully in the intervention, more family encouragement, and lower outcome expectations. Conclusions We found that psychosocial and clinical factors, along with race and ethnicity, successfully differentiated subgroups that varied in their 12‐month weight loss. Given the heterogeneity in response to behavioral obesity treatment, these results can help generate hypotheses to move intervention science toward a precision medicine approach by matching individuals to their most suitable obesity treatments.

Aims Cardiorespiratory fitness (CRF), measured by peak oxygen uptake (VO2peak), is a strong predictor of mortality. Despite its widespread clinical use, current reference equations for VO2peak show distorted calibration in obese individuals. Using data from the Fitness Registry and the Importance of Exercise National Database (FRIEND), we sought to develop novel reference equations for VO2peak better calibrated for overweight/obese individuals—in both males and females, by considering body composition metrics. Methods and results Graded treadmill tests from 6836 apparently healthy individuals were considered in data analysis. We used the National Health and Nutrition Examination Survey equations to estimate lean body mass (eLBM) and body fat percentage (eBF). Multivariable regression was used to determine sex-specific equations for predicting VO2peak considering age terms, eLBM, and eBF. The resultant equations were expressed as VO2peak (male) = 2633.4 + 48.7 × eLBM (kg) − 63.6 × eBF (%) − 0.23 × Age2 (R2 = 0.44) and VO2peak (female) = 1174.9 + 49.4 × eLBM (kg) − 21.7 × eBF (%) − 0.158 × Age2 (R2 = 0.53). These equations were well-calibrated in subgroups based on sex, age, and body mass index (BMI), in contrast to the Wasserman equation. In addition, residuals for the percent-predicted VO2peak (ppVO2) were stable over the predicted VO2peak range, with low CRF defined as <70% ppVO2 and average CRF defined between 85 and 115%. Conclusion The derived VO2peak reference equations provided physiologically explainable and were well calibrated across the spectrum of age, sex, and BMI. These equations will yield more accurate VO2peak evaluation, particularly in obese individuals.

Background Patient and clinician interest in using diet in inflammatory bowel disease (IBD) is strong, but high-quality data is limited. Cycles of a short intermittent calorie restricted diet (IRCD) have been shown to improve inflammatory and metabolic outcomes in healthy subjects, but how this translates to patients with IBD is unclear. We conducted a randomized control trial to assess the effects of IRCD on disease activity in Crohn’s disease (CD). Methods We analyzed data from 97 patients with mild to moderate CD (Crohn’s Disease Activity Index, CDAI 151-450) between the ages of 18-70 years. They were block randomized 2:1 to IRCD and control arms. Patients in the IRCD arm consumed a reduced calorie diet for only 5 consecutive days in a month (1050 calories on day 1, 800 calories for days 2-5) for 3 consecutive months, while patients in the control arm continued their usual diet. Standard of care therapy was continued during the study period. CDAI, short IBD questionnaire (SIBDQ), and patient reported outcomes (PROs) were recorded. The primary endpoint of clinical response was defined as a composite of reduction in CDAI of at least 70 points or a CDAI≤150 at the end of the 3rd 5-day diet cycle. All analyses were done by intention to treat. Results Baseline median CDAI was 198 in the IRCD group and 197 in the control arm. Forty-one patients in the IRCD arm (67.2%) and 15 patients in the control arm (44.1%) met the primary endpoint (p=0.03). Thirty-eight patients in the IRCD arm (62.3%) and 12 patients in the control arm (35.3%) achieved clinical remission (CDAI≤150) at the end of the treatment phase (p=0.018). There were no significant changes in ESR or CRP during the study period. In a post-hoc analysis, a significantly higher proportion of participants in the IRCD arm saw a decrease in baseline fecal calprotectin of at least 50% at the end of treatment versus control (p=0.019). Patients in the IRCD arm had a greater response in SIBDQ compared to the control arm at the end of treatment (p=0.01). Thirty-five patients (57.4%) in the IRCD arm and 9 patients in the control group (25.7%) reported remission by PRO (composite of ≤3 BMs/day and abdominal pain ≤1 on a 0-4 scale, p=0.032). Of note, there was no difference in therapy escalation between IRCD and control arms. Conclusion There was a significantly greater clinical response in the IRCD arm versus the control arm (p=0.03). A significant difference was also seen in key clinical secondary endpoints in favor of IRCD. The high placebo response rate could be due to several factors including standard of care therapy changes. References 1.Wei M, Brandhorst S, Shelehchi M, et al. Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular disease. Sci Transl Med. 2017;9(377). 2.Gubatan J, Kulkarni CV, Talamantes SM, Temby M, Fardeen T, Sinha SR. Dietary Exposures and Interventions in Inflammatory Bowel Disease: Current Evidence and Emerging Concepts. Nutrients. 2023;15(3):579.

Metabolic diseases such as type 2 diabetes and obesity pose a significant global health burden. Plant-based diets, including vegan diets, are linked to favorable metabolic outcomes, yet the underlying mechanisms remain unclear. In a randomized trial involving 21 pairs of identical twins, we investigated the effects of vegan and omnivorous diets on the host metabolome, immune system, and gut microbiome. Vegan diets induced significant shifts in serum and stool metabolomes, cytokine profiles, and gut microbial composition. Notably, vegan diet subjects exhibited elevated serum glycine levels despite lower dietary glycine intake, linked to reduced abundance of the gut pathobiont Bilophila wadsworthia. Functional studies demonstrated that B. wadsworthia metabolizes glycine via the glycine reductase pathway and modulates host glycine availability. Removing B. wadsworthia from gnotobiotic mice elevated glycine levels and improved metabolic markers. These findings reveal a previously underappreciated mechanism by which the gut microbiota regulates host metabolic status through diet.

Background: Self-efficacy is a modifiable intervention target in behavioral weight loss interventions. However, its role in the context of digital interventions is less clear. Purpose: To determine change in self-efficacy in a digital weight loss intervention, and whether self-efficacy is associated with engagement in self-monitoring diet or weight loss. Methods: This is a secondary analysis of the GoalTracker study among 100 adults with overweight or obesity enrolled in a 12-week standalone digital weight loss intervention emphasizing daily self-monitoring. At baseline, 1 month, and 3 months, we assessed self-efficacy for controlling eating (via the Weight Efficacy Lifestyle Questionnaire; WELQ) and self-efficacy for tracking diet. Dietary self-monitoring engagement data were collected from the MyFitnessPal app. Weight was collected in person on a calibrated scale. Analyses included participants with complete data (N range: 72-99). Results: Positive change from baseline to 1 month in self-efficacy for controlling eating was associated with higher dietary self-monitoring engagement (r = 0.21, P = .008) but not with 3-month weight change (r = -0.20, P = .052). Meanwhile, positive change from baseline to 1 month in self-efficacy for tracking diet was associated in a beneficial direction with both outcomes (r = 0.57, P < .001; r = -0.35, P < .001, respectively). However, on average, self-efficacy for controlling eating did not change over time while self-efficacy for tracking diet decreased (P < .001). Conclusion: Improvements in self-efficacy-particularly for tracking diet-early on in a digital weight loss intervention served as a mechanism of greater engagement and weight loss, highlighting the need for strengthening intervention strategies that promote early self-efficacy within a digital context.

Background Indexing peak oxygen uptake (VO2peak) to total body mass can underestimate cardiorespiratory fitness (CRF) in women, older adults, and individuals with obesity. The primary objective of this multicenter study was to derive and validate a body size-independent scaling metric for VO2peak. This metric was termed exercise body mass (EBM). Method In a cohort of apparently healthy individuals from the Fitness Registry and the Importance of Exercise National Database, we derived EBM using multivariable log-normal regression analysis. Subsequently, we developed a novel workload (WL) equation based on speed (Sp), fractional grade (fGr), and heart rate reserve (HRR). The generalized equation for VO2peak can be expressed as VO2peak = Cst × EBM × WL, where Cst is a constant representing the VO2peak equivalent of one metabolic equivalent of task. This generalized equation was externally validated using the Stanford exercise testing (SET) dataset. Results A total of 5,618 apparently healthy individuals with a respiratory exchange ratio >1.0 (57% men, mean age 44 ± 13 years) were included. The EBM was expressed as Mass (kg)0.63 × Height (m)0.53 × 1.16 (if a man) × exp (−0.39 × 10⁻⁴ × age²), which was also approximated using simple sex-specific additive equations. Unlike total body mass, EBM provided body size-independent scaling across both sexes and WL categories. The generalized VO2peak equation was expressed as 11 × EBM × [2 + Sp (in mph) × (1.06 + 5.22 × fGr) + 0.019 × HRR] and had an R² of 0.83, p < 0.001. This generalized equation mitigated bias in VO2peak estimations across age, sex, and body mass index subgroups and was validated in the SET registry, achieving an R² of 0.84 (p < 0.001). Conclusions We derived a generalized equation for measuring VO2peak during treadmill exercise testing using a novel body size-independent scaling metric. This approach significantly reduced biases in CRF estimates across age, sex, and body composition.

Introduction Despite the importance of the transition to fatherhood as a critical life stage among young adult men, much remains unknown about the factors predictive of ideal cardiovascular health (CVH) and how CVH is impacted as young men face new roles and responsibilities associated with fatherhood. Methods and analysis To address this gap, the Dad Bod Study is a prospective, longitudinal and observational study designed to examine how fatherhood affects young men’s CVH. A total of 125, first-time prospective fathers (men, 19–39 years) will be enrolled and followed over 1.5 years. Metrics of the American Heart Association’s ‘Life’s Essential 8’ as well as demographic, social and psychosocial factors will be collected at four time points (baseline (during the pregnant partner’s second trimester), 1-month post partum, 6 months post partum and 1 year post partum). The primary aims are to measure predictors of CVH among first-time fathers and describe longitudinal changes in CVH. A secondary aim is to identify the best practices for recruitment, retention and remote data collection in this population. Ethics and dissemination The study was approved by the University of California, Irvine Institutional Review Board (IRB #4907, approved 1 May 2024). Participants will provide written consent. Study data will be disseminated in manuscripts submitted to peer-reviewed journals as well as in abstracts submitted to conferences and in the resulting posters and presentations. After study completion, anonymised data and material will be made publicly available.

Higher education institutions can play an essential role in preparing students to participate in movements for just and sustainable food systems change. For the past two decades, many United States land-grant universities (LGUs) have developed food systems education (FSE) courses. This study examined the extent to which FSE courses employ four capacities deemed crucial by the FSE literature: multidimensional approaches, interdisciplinarity, centering equity, and training students to take action in food systems. The syllabi of 171 undergraduate courses at 20 LGUs were obtained by contacting instructors, and their course descriptions and learning outcomes were analyzed. This subset of LGUs were identified from the membership list of the Menus of Change University Research Collaborative (MCURC), a nationwide network of colleges using campus dining halls and classrooms as living laboratories for food systems change. Most course descriptions and learning outcomes exhibited multidimensional approaches and interdisciplinarity. However, many failed to incorporate teaching content and practices that help students critically examine equity and social justice issues in food systems, or engage in transformative change. LGUs have both the resources and urgent responsibility to empower students to be part of movements to transform unjust, unsustainable food systems. The findings of this study, and an accompanying open-access syllabus website, aim to accelerate the development of FSE curricula that prepare students to change food systems.