Chanaka N. Kahathuduwa

Physical activity and obesity: what we know and what we need to know.

Creating a negative energy balance by decreasing caloric consumption and increasing physical activity is a common strategy used to treat obesity. A large number of review and original research papers have considered the role of physical activity in weight loss and maintenance. However, their conclusions are at times conflicting. In this review, we have critically evaluated the findings of systematic reviews and meta‐analyses and supplemented their conclusions with recently published, high‐quality clinical trials. We have eliminated studies that were methodologically flawed in an attempt to reduce the ambiguity in the literature. We further sought, through selective review of these publications, to isolate the effects of various types of exercise, independent of dietary interventions, to further clarify their independent contributions. Thus, our review describes (i) combined calorie restriction with physical activity interventions, (ii) physical activity interventions without calorie restriction and (iii) the role of physical activity on maintenance of weight loss. Through this critical examination of the literature, we have provided conclusions to address certain ambiguities regarding the role of physical activity in obesity treatment that will inform clinical practice. We have also identified several long‐standing gaps in knowledge that will inform future research.

Extended calorie restriction suppresses overall and specific food cravings: a systematic review and a meta-analysis

Multiple studies have concluded that calorie restriction for at least 12 weeks is associated with reduced food cravings, while others have shown that calorie restriction may increase food cravings. We addressed this ambiguity in a systematic review and meta‐analysis.

Acute effects of theanine, caffeine and theanine–caffeine combination on attention

Objective: l-theanine is a constituent of tea which is claimed to enhance cognitive functions. We aimed to determine whether theanine and theanine–caffeine combination have acute positive effects on cognitive and neurophysiological measures of attention, compared to caffeine (a positive control) and a placebo in healthy individuals. Design: In a placebo-controlled, five-way crossover trial in 20 healthy male volunteers, we compared the effects of l-theanine (200 mg), caffeine (160 mg), their combination, black tea (one cup) and a placebo (distilled water) on cognitive (simple [SVRT] and recognition visual reaction time [RVRT]) and neurophysiological (event-related potentials [ERPs]) measures of attention. We also recorded visual (VEPs) and motor evoked potentials (MEPs) to examine any effects of treatments on peripheral visual and motor conduction, respectively. Results: Mean RVRT was significantly improved by theanine (P = 0.019), caffeine (P = 0.043), and theanine–caffeine combination (P = 0.001), but not by tea (P = 0.429) or placebo (P = 0.822). VEP or MEP latencies or SVRT did not show significant inter-treatment differences. Theanine (P = 0.001) and caffeine (P = 0.001) elicited significantly larger mean peak-to-peak N2-P300 ERP amplitudes than the placebo, whereas theanine–caffeine combination elicited a significantly larger mean N2-P300 amplitude than placebo (P < 0.001), theanine (P = 0.029) or caffeine (P = 0.005). No significant theanine × caffeine interaction was observed for RVRT or N2-P300 amplitude. Discussion: A dose of theanine equivalent of eight cups of back tea improves cognitive and neurophysiological measures of selective attention, to a degree that is comparable with that of caffeine. Theanine and caffeine seem to have additive effects on attention in high doses.

Challenges in accurately modeling the complexity of human ingestive behavior: the influence of portion size and energy density of food on fMRI food-cue reactivity

Ingestive behavior is determined by a complex interaction between neurophysiologic and behavioral and environmental contributors that begins early in life. A better understanding of this complex regulatory system is needed to account for themultifaceted nature of human ingestion. Among the influences on ingestion, increased portion size (PS) has been associated with increased energy intake independent of the energy density (ED) of food in children and adults in controlled (i.e., laboratory) and free-living conditions (1). The hedonic effects of ED have been studied in both adult and child neuroimaging studies (2, 3). In this issue of the Journal, the report by English et al. (4) on neurophysiologic correlates of PS and ED in children represents a necessary step towards furthering our understanding of these complex phenomena. English et al. (4) measured fMRI BOLD responses in healthy children (7–10 y old) during a presentation of food images representing large PS, small PS, high ED, and low ED in a blocked design and performed an exploratory whole-brain analysis to begin to shed light on brain involvement in processing of these visual cues. The authors explored the main effects of PS, ED, and their interaction with and without controlling for several covariates, including BMI z score, sex, fullness at baseline, and mean difference in liking of the stimuli within categories. Linear correlations between eating behavior questionnaires and high-ED compared with low-ED fMRI contrasts were also examined. Categorizing food stimuli on the basis of high and lowED and PS addresses an often-ignored gap in the literature, because differences in food-cue reactivity of the brain in response to PS and ED may exist that are masked when more-general food and object contrasts are considered. For instance, large PSwas associatedwith decreased BOLD responses in the inferior frontal gyrus (IFG; i.e., Brodmann area 47) compared with small PS. This contrast was driven mainly by the specific combination of large-PS, low-ED food stimuli. As the authors note, Brodmann area 47 (IFG) is often interpreted as being involved with cognitive or attentional control processes related to ingestion (5, 6). In this case, an additional interpretation could be that children simply dislike large-PS, low-ED foods and thus are not attending to them as strongly or for as much time. In subsequent analyses, the authors found that the effects of PS on the food-cue reactivity of the IFG appear to be influenced by liking of images coupled with the appetitive state (i.e., self-reported fullness). Thus, by examining the nature of the response to different aspects of the food stimuli (PS, ED), the authors provide novel insight into the need to carefully consider stimulus properties and individual context (e.g., liking, hunger or fullness) when examining the neurological underpinnings of ingestion. Paralleling previous literature on food-cue reactivity in adults, activation in a number of regions was associated with ED (7, 8). Of particular interest are the increased activations in the precentral gyrus in response to high-ED food. One plausible interpretation is an increased motor response to these images, possibly suggesting that high-ED foods may be associated with enhanced motor readiness to ingest (8). This is further supported by the negative association observed between slow eating and high-ED compared with low-ED contrast in the precentral gyrus in the current study. Finally, the authors show a significant PS 3 ED interaction in the superior temporal gyrus, which was driven by decreased reactivity to large-PS, low-ED food and increased reactivity to small-PS, low-ED food. Although the functional significance of this interaction remains to be completely understood, the demonstration that PS and ED interact in fMRI food-cue reactivity paradigms provides novel insight to guide future fMRI studies. Although English et al. provide a novel starting point for future inquiry with their approach to studying the complex ingestive process, considerable caution is urged in the interpretation and application of these findings on the basis of certain methodologic caveats. As noted by the authors, differences in visual qualities of the images (e.g., color, consistency, overall appearance) may have influenced the outcomes. This issue can be readily addressed in future studies by including control images that are matched on these dimensions (8).

Unaccounted for regression to the mean renders conclusion of article titled “Uric acid lowering in relation to HbA1c reductions with the SGLT2 inhibitor tofogliflozin” unsubstantiated

Ouchi et al. [1] reported aggregated outcomes of four clinical trials that examined the effects of the SGLT2 inhibitor tofogliflozin (vs. placebo) on HbA1c and serum uric acid levels. The authors reported that the individuals with highest levels of HbA1c experienced greater reductions in HbA1c than did persons with lower baseline HbA1c levels within the tofogliflozin arm. The authors concluded SGLT2 inhibitor tofogliflozin caused greater reductions in HbA1c among individuals with highest levels of HbA1c than it did among individuals with lower baseline levels. Furthermore, the authors reported effects of SGLT2 inhibitor on changes in serum uric acid (UA) levels being greater among those with high baseline UA levels.

Task-specific kinetic finger tremor affects the performance of carrom players.

Abstract We aimed to determine the effect of task-specific kinetic finger tremor, as indexed by surface electromyography (EMG), on the accuracy of a carrom stroke. Surface EMG of extensor digitorum communis muscle of the playing arm was recorded during rest, isometric contraction and stroke execution in 17 male carrom players with clinically observed finger tremor and 18 skill- and age-matched controls. Log-transformed power spectral densities (LogPSDs) of surface EMG activity (signifying tremor severity) at a 1-s pre-execution period correlated with angular error of the stroke. LogPSDs in 4–10 Hz range were higher in players with tremor than controls during pre-execution (P < 0.001), but not during the resting state (P = 0.067). Pre-execution tremor amplitude correlated with angular deviation (r = 0.45, P = 0.007). For the first time, we document a task-specific kinetic finger tremor in carrom players. This finger tremor during the immediate pre-execution phase appears to be a significant determinant of stroke accuracy.

Do scores on the Food Craving Inventory and Three-Factor Eating Questionnaire correlate with expected brain regions of interest in people with obesity?

OBJECTIVE To examine whether subscales of Food Craving Inventory (FCI) and Three-factor Eating Questionnaire (TFEQ) correlate with brain functional magnetic resonance imaging food-cue reactivity (fMRI-FCR) in the brain. METHODS Thirty-two male and female adults with obesity (19-60years; 30-39.9kg/m2) participated in a 3-week dietary intervention (1120kcal/day from either 1) total meal replacement shakes, 2) portion-controlled typical food. FCI, TFEQ and fMRI-FCR were measured pre- and post-intervention. Correlations between pre-intervention fMRI-FCR and standardized pre-intervention FCI and TFEQ subscales; and also post- versus pre-intervention change in fMRI-FCR (ΔfMRI-FCR) and standardized changes in FCI and TFEQ subscales were examined at the whole brain level using tools in FMRIB Software Library. RESULTS Twenty-eight subjects completed the intervention. Pre-intervention high-fat food cravings (P=0.041) and fast-food cravings (P=0.017) were negatively correlated with fMRI-FCR of several brain regions that regulate executive control over ingestion (i.e. bilateral lateral frontal pole, dorsolateral prefrontal cortex and dorsal anterior cingulate cortex). Post- vs. pre-intervention change in sweet (P=0.012) and fast food cravings (P=0.004) were negatively correlated with ΔfMRI-FCR of bilateral lateral frontal pole, dorsolateral prefrontal cortex, inferior frontal gyrus (pars opercularis) and dorsal anterior cingulate cortex (i.e. brain regions that regulate executive control over ingestion). Negative correlations were also observed between the changes in sweet and fast food cravings and ΔfMRI-FCR of brain regions that regulate food reward (i.e. bilateral mid-anterior insula, right nucleus accumbens), motor readiness to ingest (i.e. bilateral precentral gyrus), internally focused attention (i.e. bilateral precuneus and posterior cingulate cortex) and visual object recognition (i.e. occipital pole, lateral occipital cortex and middle and inferior temporal cortices). Changes in cravings for starchy food (P=0.032) and overall food cravings (P=0.027) were also negatively correlated with ΔfMRI-FCR of brain regions involved in regulating internally focused attention and visual object recognition. CONCLUSIONS In individuals with obesity, decreased food cravings seem to be reflective of increased fMRI-FCR of brain regions that regulate executive control over ingestion. Taken together, constructs measured by FCI seem to be reflective of neurophysiological processes underlying ingestive behavior and the changes in neurophysiological processes occurring during calorie restriction. CLINICAL TRIALS REGISTRY NUMBER NCT02637271; the protocol is available at https://clinicaltrials.gov/ct2/show/NCT02637271.

L-theanine and caffeine improve target-specific attention to visual stimuli by decreasing mind wandering: A human functional magnetic resonance imaging study

Oral intake of l-theanine and caffeine supplements is known to be associated with faster stimulus discrimination, possibly via improving attention to stimuli. We hypothesized that l-theanine and caffeine may be bringing about this beneficial effect by increasing attention-related neural resource allocation to target stimuli and decreasing deviation of neural resources to distractors. We used functional magnetic resonance imaging (fMRI) to test this hypothesis. Solutions of 200mg of l-theanine, 160mg of caffeine, their combination, or the vehicle (distilled water; placebo) were administered in a randomized 4-way crossover design to 9 healthy adult men. Sixty minutes after administration, a 20-minute fMRI scan was performed while the subjects performed a visual color stimulus discrimination task. l-Theanine and l-theanine-caffeine combination resulted in faster responses to targets compared with placebo (∆=27.8milliseconds, P=.018 and ∆=26.7milliseconds, P=.037, respectively). l-Theanine was associated with decreased fMRI responses to distractor stimuli in brain regions that regulate visual attention, suggesting that l-theanine may be decreasing neural resource allocation to process distractors, thus allowing to attend to targets more efficiently. l-Theanine-caffeine combination was associated with decreased fMRI responses to target stimuli as compared with distractors in several brain regions that typically show increased activation during mind wandering. Factorial analysis suggested that l-theanine and caffeine seem to have a synergistic action in decreasing mind wandering. Therefore, our hypothesis is that l-theanine and caffeine may be decreasing deviation of attention to distractors (including mind wandering); thus, enhancing attention to target stimuli was confirmed.

Is sedentary behaviour unhealthy and if so, does reducing it improve this?

To provide a qualitative synthesis of the available literature on the role of sedentary behavior in health.