David John Hume

Socio-cultural, environmental and behavioural determinants of obesity in black South African women

Summary Abstract South Africa (SA) is undergoing a rapid epidemiological transition and has the highest prevalence of obesity in sub-Saharan Africa (SSA), with black women being the most affected (obesity prevalence 31.8%). Although genetic factors are important, socio-cultural, environmental and behavioural factors, as well as the influence of socio-economic status, more likely explain the high prevalence of obesity in black SA women. This review examines these determinants in black SA women, and compares them to their white counterparts, black SA men, and where appropriate, to women from SSA. Specifically this review focuses on environmental factors influencing obesity, the influence of urbanisation, as well as the interaction with socio-cultural and socio-economic factors. In addition, the role of maternal and early life factors and cultural aspects relating to body image are discussed. This information can be used to guide public health interventions aimed at reducing obesity in black SA women.

Electrophysiological indices of visual food cue-reactivity. Differences in obese, overweight and normal weight women

Heightened food cue-reactivity in overweight and obese individuals has been related to aberrant functioning of neural circuitry implicated in motivational behaviours and reward-seeking. Here we explore the neurophysiology of visual food cue-reactivity in overweight and obese women, as compared with normal weight women, by assessing differences in cortical arousal and attentional processing elicited by food and neutral image inserts in a Stroop task with record of EEG spectral band power and ERP responses. Results show excess right frontal (F8) and left central (C3) relative beta band activity in overweight women during food task performance (indicative of pronounced early visual cue-reactivity) and blunted prefrontal (Fp1 and Fp2) theta band activity in obese women during office task performance (suggestive of executive dysfunction). Moreover, as compared to normal weight women, food images elicited greater right parietal (P4) ERP P200 amplitude in overweight women (denoting pronounced early attentional processing) and shorter right parietal (P4) ERP P300 latency in obese women (signifying enhanced and efficient maintained attentional processing). Differential measures of cortical arousal and attentional processing showed significant correlations with self-reported eating behaviour and body shape dissatisfaction, as well as with objectively assessed percent fat mass. The findings of the present study suggest that heightened food cue-reactivity can be neurophysiologically measured, that different neural circuits are implicated in the pathogenesis of overweight and obesity, and that EEG techniques may serve useful in the identification of endophenotypic markers associated with an increased risk of externally mediated food consumption.

The Role of Adipose Tissue in Insulin Resistance in Women of African Ancestry

Women of African ancestry, particularly those living in industrialized countries, experience a disproportionately higher prevalence of type 2 diabetes (T2D) compared to their white counterparts. Similarly, obesity and insulin resistance, which are major risk factors for T2D, are greater in black compared to white women. The exact mechanisms underlying these phenomena are not known. This paper will focus on the role of adipose tissue biology. Firstly, the characteristic body fat distribution of women of African ancestry will be discussed, followed by the depot-specific associations with insulin resistance. Factors involved in adipose tissue biology and their relation to insulin sensitivity will then be explored, including the role of sex hormones, glucocorticoid metabolism, lipolysis and adipogenesis, and their consequent effects on adipose tissue hypoxia, oxidative stress, and inflammation. Finally the role of ectopic fat deposition will be discussed. The paper proposes directions for future research, in particular highlighting the need for longitudinal and/or intervention studies to better understand the mechanisms underlying the high prevalence of insulin resistance and T2D in women of African ancestry.

Low energy intake plus low energy expenditure (low energy flux), not energy surfeit, predicts future body fat gain

BACKGROUND There is a paucity of studies that have prospectively tested the energy surfeit theory of obesity with the use of objectively estimated energy intake and energy expenditure in humans. An alternative theory is that homeostatic regulation of body weight is more effective when energy intake and expenditure are both high (high energy flux), implying that low energy flux should predict weight gain. OBJECTIVE We aimed to examine the predictive relations of energy balance and energy flux to future weight gain and tested whether results were replicable in 2 independent samples. DESIGN Adolescents (n = 154) and college-aged women (n = 75) underwent 2-wk objective doubly labeled water, resting metabolic rate, and percentage of body fat measures at baseline. Percentage of body fat was measured annually for 3 y of follow-up for the adolescent sample and for 2 y of follow-up for the young adult sample. RESULTS Low energy flux, but not energy surfeit, predicted future increases in body fat in both studies. Furthermore, high energy flux appeared to prevent fat gain in part because it was associated with a higher resting metabolic rate. CONCLUSION Counter to the energy surfeit model of obesity, results suggest that increasing energy expenditure may be more effective for reducing body fat than caloric restriction, which is currently the treatment of choice for obesity. This trial was registered at clinicaltrials.gov as NCT02084836.

The metabolic effects of a commercially available chicken peri-peri (African bird’s eye chilli) meal in overweight individuals

A growing body of evidence suggests that capsaicin ingestion may lead to desirable metabolic outcomes; however, the results in humans are equivocal. Whether or not benefits may be gained from ingestion of capsaicin via a commercially available meal has not been determined. The objectives of this randomised, cross-over intervention study were to compare the 2 h postprandial effects of a standard commercially prepared meal containing chilli (HOT, 5·82 mg total capsaicinoids) with a similar meal with no chilli (CON, 25 kg/m2 and a waist circumference >94 cm (men) or 80 cm (women), were studied. Participants had normal glucose tolerance and were accustomed, but were not regular chilli eaters. A paired t test indicated that insulin AUC was smaller following the HOT meal (P=0·002). Similarly, there was a tendency for glucose AUC to be reduced following the HOT meal (P=0·056). No discernable effects of the HOT meal were observed on metabolic rate, core temperature, hs-CRP concentrations and endothelial-dependent microvascular reactivity. The results from this study indicate that a standard restaurant meal containing a relatively small dose of capsaicin delivered via African birds eye chilli, which is currently available to the public, results in lower postprandial insulin concentrations in overweight individuals, compared with the same meal without chilli.

Cognitive control over visual food cue saliency is greater in reduced-overweight/obese but not in weight relapsed women: An EEG study.

OBJECTIVE Poor weight management may relate to a reduction in neurobehavioural control over food intake and heightened reactivity of the brains neural reward pathways. Here we explore the neurophysiology of food-related visual cue processing in weight reduced and weight relapsed women by assessing differences in cortical arousal and attentional processing using a food-Stroop paradigm. METHODS 51 women were recruited into 4 groups: reduced-weight participants (RED, n=14) compared to BMI matched low-weight controls (LW-CTL, n=18); and weight relapsed participants (REL, n=10) compared to BMI matched high-weight controls (HW-CTL, n=9). Eating behaviour and body image questionnaires were completed. Two Stroop tasks (one containing food images, the other containing neutral images) were completed with record of electroencephalography (EEG). RESULTS Differences in cortical arousal were found in RED versus LW-CTL women, and were seen during food task execution only. Compared to their controls, RED women exhibited lower relative delta band power (p=0.01) and higher relative beta band power (p=0.01) over the right frontal cortex (F4). Within the RED group, delta band oscillations correlated positively with self-reported habitual fat intake and with body shape dissatisfaction. CONCLUSIONS As compared to women matched for phenotype but with no history of weight reduction, reduced-overweight/obese women show increased neurobehavioural control over external food cues and the inhibition of reward-orientated feeding responses. Insight into these self-regulatory mechanisms which attenuate food cue saliency may aid in the development of cognitive remediation therapies which facilitate long-term weight loss.

The Role of the Medical Health Humanities in the Study of Mental Health in Family Medicine

While biomedical journals and medical school curricula have adopted some of the principles of the medical health humanities [1], numerous empirical texts continue to negate the social, political, cultural and economic forces which shape individual choices in the daily lived context. The principles of family medicine furthermore dictate that patient-centered healthcare and the impact of medical treatments permeate beyond the clinical sphere and act as forces upon domestic, familial, occupational and community-based settings. Historically, the patient’s mental health status and psychosocial wellbeing, in particular, have been neglected in the clinical interview and as being implicated in the aetiology, pathogenesis and chronicity of both communicable disease, and non-communicable diseases of lifestyle.

Healthy Restrained Eaters Diminish Consummatory Food Reward and Inhibit Prepotent Feeding Responses: An EEG Study

Background: Some individuals with modest elevations in dietary restraint exhibit the ability to diminish consummatory and anticipatory food reward. In this paper we aim to identify the underlying mechanisms of food-specific cortical inhibition responses in restrained vs unrestrained eaters. Methods: Restrained (n = 43) and unrestrained eaters (n = 38) completed self-report surveys and a food- vs non-food Stroop task protocol with record of electroencephalography (EEG). Cortical rhythms and EEG ERPs were assessed. Results: Compared to their unrestrained peers, restrained eaters showed several differences in food task-related event-related potential (ERP) waveform presentation: ERP P300 component latency was significantly longer during food image viewing over the left parietal cortex (P3), and the amplitudes of the ERP P300 and LPP components were significantly greater over the right central electrode (C4) whilst responding to Stroop color-word cues. Food task-related conflict cue elicited ERP P300 amplitude correlated positively with eating restraint, and negatively with bioelectrical impedance assessed % body fat. Conclusions: Restrained eaters free of eating pathology attenuate conscious visual food cue processing and show enhanced executive brain functioning during late attentional processing despite the presence of distractor food cues. Our data propose robust executive governance as the primary underlying neurophysiological mechanism by which healthy restrained eaters diminish consummatory food reward and inhibit prepotent feeding responses.

Successful and unsuccessful weight-loss maintainers: strategies to counteract metabolic compensation following weight loss

Adaptive thermogenesis and reduced fat oxidative capacity may accompany weight loss, continuing in weight maintenance. The present study aimed (1) to determine whether weight-reduced and weight-loss relapsed women are at greater metabolic risk for weight gain compared with BMI-matched controls with no weight-loss history, and (2) to identify protective strategies that might attenuate weight loss-associated adaptive thermogenesis and support successful weight-loss maintenance. Four groups of women were recruited: reduced-overweight/obese (RED, n 15), controls (low-weight stable weight; LSW, n 19) BMI <27 kg/m2; relapsed-overweight/obese (REL, n 11), controls (overweight/obese stable weight; OSW, n 11) BMI >27 kg/m2. Body composition (bioelectrical impedance), 75 g oral glucose tolerance test, fasting and postprandial metabolic rate (MR) and substrate utilisation (RER) and physical activity (accelerometer (7 d)) were measured. Sociobehavioural questionnaires and 3 × 24 h diet recalls were completed. Fasting and postprandial MR, RER and total daily energy intake (TDEI) were not different between RED and REL v. controls (P > 0·05). RED consumed less carbohydrate (44·8 (sd 10·3) v. 53·4 (sd 10·0) % TDEI, P = 0·020), more protein (19·2 (sd 6·0) v. 15·6 (sd 4·2) % TDEI, P = 0·049) and increased physical activity, but behaviourally reported greater dietary restraint (P = 0·002) compared with controls. TDEI, macronutrient intake and physical activity were similar between OSW and REL. REL reported higher subjective fasting and lower postprandial ratings of prospective food consumption compared with OSW. Weight-reduced women had similar RMR (adjusted for fat-free mass) compared with controls with no weight-loss history. Increased physical activity, higher protein intake and greater lean muscle mass may have counteracted weight loss-associated metabolic compensation and highlights their importance in weight-maintenance programmes.