Lean and obese dietary phenotypes: differences in energy and substrate metabolism and appetite.

This study aimed to characterise lean and obese phenotypes according to diet and body composition, and to compare fasting and postprandial appetite and metabolic profiles following a high-fat test meal. A total of ten lean (BMI40 and 30 kg/m2) high-fat consumers (OHF; >40 % energy from fat) were recruited. Before and following the test meal (4727 kJ (1130 kcal), 77 % fat, 20 % carbohydrate (CHO) and 3 % protein), fasting plasma glucose, insulin, leptin, ghrelin, peptide YY (PYY), RER, RMR and subjective appetite ratings (AR) were measured for 6 h. Thereafter, subjects consumed a self-selected portion of a standardised post-test meal (40 % fat, 45 % CHO and 15 % protein) and reported AR. Fasting (P=0·01) and postprandial (P<0·001) fat oxidation was significantly higher in LHF than in LLF but was not different between LHF and OHF. Although similar between the lean groups, fasting and postprandial energy expenditures were significantly higher in OHF compared with LHF (P<0·01). Despite similar AR across groups, LLF consumed a relatively greater quantity of the post-test meal than did LHF (7·87 (sd 2·96) v. 7·23 (sd 2·67) g/kg, P=0·013). The lean groups showed appropriate changes in plasma ghrelin and PYY following the test meal, whereas the OHF group showed a blunted response. In conclusion, the LHF phenotype had a greater capacity for fat oxidation, which may be protective against weight gain. OHF individuals had a blunted appetite hormone response to the high-fat test meal, which may subsequently increase energy intake, driving further weight gain.

Improved Sleep Quality and Depressive Symptoms With Exercise Training in Obese Women From a Low Socioeconomic Community: A Randomized Controlled Trial.

BACKGROUND: Improving sleep quality and reducing depressive symptoms may be target mechanisms for intervention-based research aimed at reducing cardiometabolic risk in low-income communities. This study assessed the effects of exercise training on depressive symptoms and sleep in obese women for a low socioeconomic community. The secondary aim explored associations between changes in depressive symptoms and sleep with changes in cardiorespiratory fitness and cardiometabolic risk factors. METHODS: Participants were randomized into exercise (n = 20) or control (n = 15) groups. The exercise group completed 12 weeks of combined resistance and aerobic training (40-60 min, 4 d/wk), and the control group maintained habitual diet and activity. Preintervention and postintervention testing included questionnaires on symptoms of depression, psychological distress, and sleep quality. Sedentary time, peak oxygen consumption, body mass index, and insulin sensitivity were measured objectively. Sleep duration (accelerometry) was assessed at preintervention and weeks 4, 8, and 12. RESULTS: Exercise training reduced depressive symptoms (P = .002) and improved sleep quality (P < .001) and sleep efficiency (P = .005). Reduced depressive symptoms were associated with improved peak oxygen consumption (rho = -.600, P < .001), and improved sleep quality correlated with reduced sedentary time (rho = .415, P = .018). CONCLUSION: These results highlight the potential for community-based exercise interventions to simultaneously address multiple comorbidities in a low-income setting.

Higher baseline fat oxidation promotes gynoid fat mobilization in response to a 12-week exercise intervention in sedentary, obese black South African women.

This 12-week exercise intervention study assessed changes in cardiorespiratory fitness (CRF), energy expenditure (EE), and substrate utilisation at rest and during exercise in obese, black South African (SA) women and explored associations with changes in body composition. Black SA women (body mass index: 30-40 kg·m-2, age: 20-35 years) were randomised into control (CTL; n = 15, maintaining usual activity) or exercise (EXE; n = 20; 12 weeks, 4 days·week-1, 40-60 min·day-1 at >70% peak heart rate) groups. Pre- and post-intervention testing included peak oxygen consumption, resting and steady state (50% peak oxygen consumption) EE, respiratory exchange, and body composition (dual-energy X-ray absorptiometry). Dietary intake (4-day) and daily step-count (ActivPAL, activPAL3c; PAL Technologies Ltd, Glasgow, UK) was collected at pre-testing and at 4, 8, and 12 weeks. EXE increased peak oxygen consumption (24.9 ± 2.4 to 27.6 ± 3.4 mL·min-1·kg-1; p < 0.001) and steady state fat oxidation rates (7.5 ± 2.5 to 9.0 ± 2.7 mg·min-1·kg-1 fat-free soft tissue mass; p = 0.003) (same relative exercise intensity). CTL remained unchanged (p > 0.05). EXE reduced proportional gynoid fat mass (percentage total fat mass, p = 0.002). Baseline resting carbohydrate oxidation rates (p = 0.036) and steady state fat oxidation rates (p = 0.021) explained 60.6% of the variability in Δgynoid fat mass (p < 0.001) in EXE. This 12-week exercise intervention improved CRF and steady state fat oxidation rates. Greater reliance on fat oxidation at baseline promoted proportional reductions in gynoid, not visceral, fat mass in response to exercise training. Novelty Combined exercise training in obese black South African women increased cardiorespiratory fitness and rates of fat oxidation during steady state exercise. Exercise training reduced proportional gynoid, not visceral, fat, potentially representing an ethnic/sex-specific response. Baseline substrate utilisation (resting and steady state exercise (50% peak oxygen uptake)) predicted changes in gynoid fat mass.

Exercise Training Alters Red Blood Cell Fatty Acid Desaturase Indices and Adipose Tissue Fatty Acid Profile in African Women with Obesity.

OBJECTIVE: This study assessed the changes in red blood cell total phospholipid (RBC-TPL) and subcutaneous adipose tissue (SAT) fatty acid (FA) composition in response to 12 weeks of exercise training in South African women with obesity and the associations with changes in cardiometabolic risk factors. METHODS: Previously sedentary women were randomized into control (n = 15) or exercise (n = 20) groups. RBC-TPL and SAT FA profiles, SAT gene expression, systemic inflammatory markers, liver fat, and insulin sensitivity (SI ) were measured before and after the intervention. RESULTS: Compared with control, exercise training induced decreases in RBC-TPL dihomo-γ-linolenic acid content and stearoyl-CoA desaturase-1 and increased delta-5 desaturase-estimated activity (P < 0.05). In the combined group, these changes correlated with changes in circulating leptin and TNFα (P < 0.05), as well as lower liver fat (P < 0.01). Exercise training decreased saturated FA (lauric and myristic acids) and increased polyunsaturated FA (eicosadienoic and adrenic acids) (P < 0.05) in abdominal SAT, whereas γ-linolenic acid decreased (P < 0.01) in gluteal SAT. These changes in RBC-TPL and SAT FA compositions were not associated with changes in SAT gene expression and SI . CONCLUSIONS: Exercise training alters RBC-TPL desaturase activities, which correlate with lower liver fat and systemic inflammation but not with the improvement of SI .

Effect of exercise training on insulin sensitivity, hyperinsulinemia and ectopic fat in black South African women: a randomized controlled trial.

OBJECTIVE: We investigated the effects of a 12-week exercise intervention on insulin sensitivity (SI) and hyperinsulinemia and associated changes in regional and ectopic fat. RESEARCH DESIGN AND METHODS: Healthy, black South African women with obesity (mean age 23 ± 3.5 years) and of isiXhosa ancestry were randomised into a 12-week aerobic and resistance exercise training group (n = 23) and a no exercise group (control, n = 22). Pre and post-intervention testing included assessment of SI, insulin response to glucose (AIRg), insulin secretion rate (ISR), hepatic insulin extraction (FEL) and disposition index (DI) (AIRg × SI) (frequently sampled i.v. glucose tolerance test); fat mass and regional adiposity (dual-energy X-ray absorptiometry); hepatic, pancreatic and skeletal muscle fat content and abdominal s.c. and visceral adipose tissue volumes (MRI). RESULTS: Exercise training increased VO2peak (mean ± s.d.: 24.9 ± 2.42 to 27.6 ± 3.39 mL/kg/min, P < 0.001), SI (2.0 (1.2-2.8) to 2.2 (1.5-3.7) (mU/l)-1 min-1, P = 0.005) and DI (median (interquartile range): 6.1 (3.6-7.1) to 6.5 (5.6-9.2) × 103 arbitrary units, P = 0.028), and decreased gynoid fat mass (18.5 ± 1.7 to 18.2 ± 1.6%, P < 0.001) and body weight (84.1 ± 8.7 to 83.3 ± .9.7 kg, P = 0.038). None of these changes were observed in the control group, but body weight increased (P = 0.030). AIRg, ISR and FEL, VAT, SAT and ectopic fat were unaltered after exercise training. The increase in SI and DI were not associated with changes in regional or ectopic fat. CONCLUSION: Exercise training increased SI independent from changes in hyperinsulinemia and ectopic fat, suggesting that ectopic fat might not be a principal determinant of insulin resistance in this cohort.

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.

An Exercise Intervention to Unravel the Mechanisms Underlying Insulin Resistance in a Cohort of Black South African Women: Protocol for a Randomized Controlled Trial and Baseline Characteristics of Participants.

BACKGROUND: The pathogenesis of type 2 diabetes (T2D) in black African women is complex and differs from that in their white counterparts. However, earlier studies have been cross-sectional and provide little insight into the causal pathways. Exercise training is consistently used as a model to examine the mechanisms underlying insulin resistance and risk for T2D. OBJECTIVE: The objective of the study was to examine the mechanisms underlying the changes in insulin sensitivity and secretion in response to a 12-week exercise intervention in obese black South African (SA) women. METHODS: A total of 45 obese (body mass index, BMI: 30-40 kg/m2) black SA women were randomized into a control (n=22) or experimental (exercise; n=23) group. The exercise group completed 12 weeks of supervised combined aerobic and resistance training (40-60 min, 4 days/week), while the control group maintained their typical physical activity patterns, and both groups were requested not to change their dietary patterns. Before and following the 12-week intervention period, insulin sensitivity and secretion (frequently sampled intravenous glucose tolerance test) and its primary and secondary determinants were measured. Dietary intake, sleep quality and quantity, physical activity, and sedentary behaviors were measured every 4 weeks. RESULTS: The final sample included 20 exercise and 15 control participants. Baseline sociodemographics, cardiorespiratory fitness, anthropometry, cardiometabolic risk factors, physical activity, and diet did not differ between the groups (P>.05). CONCLUSIONS: The study describes a research protocol for an exercise intervention to understand the mechanisms underlying insulin sensitivity and secretion in obese black SA women and aims to identify causal pathways underlying the high prevalence of insulin resistance and risk for T2D in black SA women, targeting specific areas for therapeutic intervention. TRIAL REGISTRATION: Pan African Clinical Trial Registry PACTR201711002789113; http://www.pactr.org/ATMWeb/ appmanager/atm/atmregistry?_nfpb=true&_pageLabel=portals_app_atmregistry_portal_page_13 (Archived by WebCite at http://www.webcitation.org/6xLEFqKr0).

Compensations for Weight Loss in Successful and Unsuccessful Dieters.

OBJECTIVES: To explore for the presence of behavioral compensation for weight loss in successful and unsuccessful dieters. METHODS: Successful dieters (women maintaining a weight loss ≥ 10% body weight for ≥ 1 year) and unsuccessful dieters (women who had lost and regained ≥ 10% body weight) were compared to age- and BMI-matched controls for measures obtained from self-report surveys, an online dietary recall, indirect calorimetry, a submaximal treadmill test, and accelerometry. RESULTS: Compared to their controls, successful dieters reported lower carbohydrate intake, greater protein intake, greater eating restraint, and more vigorous intensity physical activity. Accelerometry data reflected more moderate-to-vigorous intensity physical activity, but more energy expenditure over-report in successful dieters than their comparators. Unsuccessful dieters were indistinguishable from their controls. CONCLUSIONS: Successful dieters show behavioral vigilance but over-report total daily energy expenditure, whereas unsuccessful dieters do not demonstrate measurable compensations in health behavior.