Impact of Intensive Lifestyle Intervention on Neural Food Cue Reactivity: Action for Health in Diabetes Brain Ancillary Study

Obesity surgery and neural correlates of human eating behaviour: A systematic review of functional MRI studies

Changes in eating behaviour including reductions in appetite and food intake, and healthier food cue reactivity, reward, hedonics and potentially also preference, contribute to weight loss and its health benefits after obesity surgery. Functional magnetic resonance imaging (fMRI) has been increasingly used to interrogate the neural correlates of eating behaviour in obesity, including brain reward-cognitive systems, changes after obesity surgery, and links with alterations in the gut-hormone-brain axis. Neural responses to food cues can be measured by changes in blood oxygen level dependent (BOLD) signal in brain regions involved in reward processing, including caudate, putamen, nucleus accumbens, insula, amygdala, orbitofrontal cortex, and top-down inhibitory control, including dorsolateral prefrontal cortex (dlPFC). This systematic review aimed to examine: (i) results of human fMRI studies involving obesity surgery, (ii) important methodological differences in study design across studies, and (iii) correlations and associations of fMRI findings with clinical outcomes, other eating behaviour measures and mechanistic measures. Of 741 articles identified, 23 were eligible for inclusion: 16 (69.6%) longitudinal, two (8.7%) predictive, and five (21.7%) cross-sectional studies. Seventeen studies (77.3%) included patients having Roux-en-Y gastric bypass (RYGB) surgery, six (26.1%) vertical sleeve gastrectomy (VSG), and five (21.7%) laparoscopic adjustable gastric banding (LAGB). The majority of studies (86.0%) were identified as having a very low risk of bias, though only six (27.3%) were controlled interventional studies, with none including randomisation to surgical and control interventions. The remaining studies (14.0%) had a low risk of bias driven by their control groups not having an active treatment. After RYGB surgery, food cue reactivity often decreased or was unchanged in brain reward systems, and there were inconsistent findings as to whether reductions in food cue reactivity was greater for high-energy than low-energy foods. There was minimal evidence from studies of VSG and LAGB surgeries for changes in food cue reactivity in brain reward systems, though effects of VSG surgery on food cue reactivity in the dlPFC were more consistently found. There was consistent evidence for post-operative increases in satiety gut hormones glucagon-like-peptide 1 (GLP-1) and peptide YY (PYY) mediating reduced food cue reactivity after RYGB surgery, including two interventional studies. Methodological heterogeneity across studies, including nutritional state, nature of food cues, post-operative timing, lack of control groups for order effects and weight loss or dietary/psychological advice, and often small sample sizes, limited the conclusions that could be drawn, especially for correlational analyses with clinical outcomes, other eating behaviour measures and potential mediators. This systematic review provides a detailed data resource for those performing or analysing fMRI studies of obesity surgery and makes suggestions to help improve reporting and design of such studies, as well as future directions.

Neuroimaging Investigations of Obesity: a Review of the Treatment of Sex from 2010

PURPOSE OF REVIEW

To summarize the results of adult obesity neuroimaging studies (structural, resting-state, task-based, diffusion tensor imaging) published from 2010, with a focus on the treatment of sex as an important biological variable in the analysis, and identify gaps in sex difference research.

RECENT FINDINGS

Neuroimaging studies have shown obesity-related changes in brain structure, function, and connectivity. However, relevant factors such as sex are often not considered. We conducted a systematic review and keyword co-occurrence analysis. Literature searches identified 6281 articles, of which 199 met inclusion criteria. Among these, only 26 (13%) considered sex as an important variable in the analysis, directly comparing the sexes (n = 10; 5%) or providing single-sex/disaggregated data (n = 16, 8%); the remaining studies controlled for sex (n = 120, 60%) or did not consider sex in the analysis (n = 53, 27%). Synthesizing sex-based results, obesity-related parameters (e.g., body mass index, waist circumference, obese status) may be generally associated with more robust morphological alterations in men and more robust structural connectivity alterations in women. Additionally, women with obesity generally expressed increased reactivity in affect-related regions, while men with obesity generally expressed increased reactivity in motor-related regions; this was especially true under a fed state. The keyword co-occurrence analysis indicated that sex difference research was especially lacking in intervention studies. Thus, although sex differences in the brain associated with obesity are known to exist, a large proportion of the literature informing the research and treatment strategies of today has not specifically examined sex effects, which is needed to optimize treatment.

Neural responses to food cues in middle to older aged adults: a scoping review of fMRI studies

AIM

Understanding neural responses through functional magnetic resonance imaging (fMRI) to food and food cues in middle-older adults may lead to better treatment options to address the growing issue of malnutrition. This scoping review aimed to determine the extent, range and nature of research using fMRI, related to reward-based regions, in response to food cues in middle to older aged adults (50 years and over).

METHODS

The following databases were systematically searched in July 2019: CINAHL, CENTRAL, Embase, Dissertations and Theses, Ovid Medline, PsycINFO, PsycEXTRA, Scopus and Web of Science. Studies were eligible for inclusion if participants had a mean or median age ≥50 years, utilised and reported outcomes of either a food cue task-related fMRI methodology or resting-state fMRI. Data from included studies were charted, and synthesised narratively.

RESULTS

Twenty-two studies were included. Eighteen studies utilised a task-related design to measure neural activation, two studies measured resting state neural connectivity only and an additional two studies measured both. The fMRI scanning paradigms, food cue tools and procedure of presentation varied markedly. Four studies compared the neural responses to food between younger and older adults, providing no consensus on neural age-related changes to food cues; two studies utilised longitudinal scans.

CONCLUSION

This review identified significant extent, range and nature in the approaches used to assess neuronal activity in response to food cues in adults aged 50 years and over. Future studies are needed to understand the age-related appetite changes whilst considering personal preferences for food cues.

The ENGAGE-2 study: Engaging self-regulation targets to understand the mechanisms of behavior change and improve mood and weight outcomes in a randomized controlled trial (Phase 2)

Despite evidence for effective integrated behavior therapy for treating comorbid obesity and depression, treatment response is highly variable and the underlying neurobiological mechanisms remain unknown. This hampers efforts to identify mechanistic targets in order to optimize treatment precision and potency. Funded within the NIH Science of Behavior Change (SOBC) Research Network, the 2-phased ENGAGE research project applies an experimental precision medicine approach to address this gap. The Phase 1 study focused on demonstrating technical feasibility, target engagement and potential neural mechanisms of responses to an integrated behavior therapy. This therapy combines a video-based behavioral weight loss program and problem-solving therapy for depression, with as-needed intensification of antidepressant medications, and its clinical effectiveness was demonstrated within a parent randomized clinical trial. Here, we describe the ENGAGE Phase 2 (ENGAGE-2) study protocol which builds on Phase 1 in 2 ways: (1) pilot testing of an motivational interviewing-enhanced, integrated behavior therapy in an independent, primarily minority patient sample, and (2) evaluation of a priori defined neural targets, specifically the negative affect (threat and sadness) circuits which demonstrated engagement and malleability in Phase 1, as mediators of therapeutic outcomes. Additionally, the Phase 2 study includes a conceptual and methodological extension to explore the role of microbiome-gut-brain and systemic immunological pathways in integrated behavioral treatment of obesity and depression. This protocol paper documents the conceptualization, design and the transdisciplinary methodologies in ENGAGE-2, which can inform future clinical and translational research in experimental precision medicine for behavior change and chronic disease management. Trial registration: ClinicalTrials.gov #NCT 03,841,682.

Effects of Cognitive Strategies on Neural Food Cue Reactivity in Adults with Overweight/Obesity

OBJECTIVE

Functional magnetic resonance imaging (fMRI) studies of obesity have revealed key roles for reward-related and inhibitory control-related activity in response to food cues. This study examines how cognitive strategies impact neural food cue reactivity.

METHODS

In a within-participants, block-design, fMRI paradigm, 30 participants (24 women; mean BMI = 31.8) used four mind-sets while viewing food: "distract" (cognitive behavioral therapy based), "allow" (acceptance and commitment therapy based), "later" (focusing on long-term negative consequences), and "now" (control; focusing on immediate rewards). Participants rated cravings by noting urges to eat on four-point Likert scales after each block.

RESULTS

Self-reported cravings significantly differed among all conditions (pairwise comparisons P < 0.05). Cravings were lowest when participants considered long-term consequences (LATER mind-set: 1.7 [SD 0.7]), were significantly higher when participants used the DISTRACT (1.9 [SD 0.7]) and ALLOW (2.3 [SD 0.9]) mind-sets, and were highest when participants used the NOW mind-set (3.2 [SD 0.7]). These behavioral differences were accompanied by differences in neural food cue reactivity. The LATER mind-set (long-term consequences) led to greater inhibitory-control activity in the dorsolateral prefrontal cortex. The cognitive behavioral therapy-based DISTRACT mind-set was associated with greater activity in executive function and reward-processing areas, whereas the ALLOW mind-set (acceptance and commitment therapy) elicited widespread activity in frontal, reward-processing, and default-mode regions.

CONCLUSIONS

Because focusing on negative long-term consequences led to the greatest decrease in cravings and increased inhibitory control, this may be a promising treatment strategy for obesity.