Effects of weight gain and weight loss on regional fat distribution

Impact of baseline adipose tissue characteristics on change in adipose tissue volume during a low calorie diet in people with obesity-results from the LION study

BACKGROUND/OBJECTIVES

Weight loss outcomes vary individually. Magnetic resonance imaging (MRI)-based evaluation of adipose tissue (AT) might help to identify AT characteristics that predict AT loss. This study aimed to assess the impact of an 8-week low-calorie diet (LCD) on different AT depots and to identify predictors of short-term AT loss using MRI in adults with obesity.

METHODS

Eighty-one adults with obesity (mean BMI 34.08 ± 2.75 kg/m², mean age 46.3 ± 10.97 years, 49 females) prospectively underwent baseline MRI (liver dome to femoral head) and anthropometric measurements (BMI, waist-to-hip-ratio, body fat), followed by a post-LCD-examination. Visceral and subcutaneous AT (VAT and SAT) volumes and AT fat fraction were extracted from the MRI data. Apparent lipid volumes based on MRI were calculated as approximation for the lipid contained in the AT. SAT and VAT volumes were subdivided into equidistant thirds along the craniocaudal axis and normalized by length of the segmentation. T-tests compared baseline and follow-up measurements and sex differences. Effect sizes on subdivided AT volumes were compared. Spearman Rank correlation explored associations between baseline parameters and AT loss. Multiple regression analysis identified baseline predictors for AT loss.

RESULTS

Following the LCD, participants exhibited significant weight loss (11.61 ± 3.07 kg, p < 0.01) and reductions in all MRI-based AT parameters (p < 0.01). Absolute SAT loss exceeded VAT loss, while relative apparent lipid loss was higher in VAT (both p < 0.01). The lower abdominopelvic third showed the most significant SAT and VAT reduction. The predictor of most AT and apparent lipid losses was the normalized baseline SAT volume in the lower abdominopelvic third, with smaller volumes favoring greater AT loss (p < 0.01 for SAT and VAT loss and SAT apparent lipid volume loss).

CONCLUSIONS

The LCD primarily reduces lower abdominopelvic SAT and VAT. Furthermore, lower abdominopelvic SAT volume was detected as a potential predictor for short-term AT loss in persons with obesity.

Weight status changes from childhood to adulthood were associated with cardiometabolic outcomes in adulthood

AIM

Few studies have assessed the association between weight changes from childhood to adulthood and cardiometabolic factors in adulthood. The aim of this study was to explore the relationships between weight changes from childhood to adulthood and cardiometabolic factors in adulthood using national Chinese data.

METHODS

We included 649 participants from the China Health and Nutrition Survey from 1989 to 2009 and divided them into four groups by their body mass index from 6 to 37 years of age. They were selected using multistage random cluster sampling from 15 areas with large variations in economic and social development. Poisson regression models assessed associations between weight status changes and cardiometabolic outcomes in adulthood.

RESULTS

The risk of multiple abnormal cardiometabolic outcomes in adulthood was increased in the 126 subjects with normal weight in childhood but overweight or obesity in adulthood and the 28 with obesity at both ages, compared to the 462 with normal weight at both ages. There was insufficient evidence to demonstrate that the 33 who had weight issues as children, but not as adults, had an increased risk.

CONCLUSION

Being overweight or obese in both childhood and adulthood or during adulthood only increased the risk of abnormal cardiometabolic outcomes in adulthood. Larger studies need to investigate whether weight problems in childhood, but not adulthood, increase the risk.

Low Calf Circumference is Associated with Prolonged Hospital Stay in Older Patients with Solid Tumors: A Secondary Analysis of a Cohort Study

BACKGROUND

Older patients with cancer present intense loss of muscle mass (MM). Calf circumference (CC) is a simple measurement that assesses MM. This study analyzed the accuracy and association between low CC and negative outcomes in older patients with solid tumors.

METHODS

A secondary analysis of a prospective cohort study of inpatients with cancer was conducted. Low CC was defined as CC ≤34 cm in males and ≤33 cm in females. The CC was adjusted for body mass index by reducing 3 or 7 cm for BMI (in kg/m2) of 25-29.9 and 30-39.9, respectively. Accuracy tests and regression analyses were performed to evaluate the criterion validity of low CC for predicting length of stay (LOS) and readmission.

RESULTS

A total of 248 inpatients were evaluated (69.7 [standard deviation (SD) 7.2]; 59.7% men). Among them, 31% had a low CC. A low CC (crude and adjusted for BMI) showed poor performance in predicting LOS and readmission. In the adjusted analysis, older patients with low CC had a 2.45-fold increased risk of LOS ≥ 4 days.

CONCLUSION

Low CC did not perform well in predicting negative outcomes in older patients with solid tumors. However, low CC was positively associated with LOS.

Effects of repeated weight cycling on non-alcoholic steatohepatitis in diet-induced obese mice

Lifestyle interventions remain the treatment of choice for patients with obesity and metabolic complications, yet are difficult to maintain and often lead to cycles of weight loss and regain (weight cycling). Literature on weight cycling remains controversial and we therefore investigated the association between weight cycling and metabolic complications using preexistent obese mice. Ldlr-/-.Leiden mice received a high-fat diet (HFD) for 20 weeks to induce obesity. Subsequently, weight-cycled mice were switched between the healthy chow diet and HFD for four 2-week periods and compared to mice that received HFD for the total study period. Repeated weight cycling tended to decrease body weight and significantly reduced fat mass, whereas adipose tissue inflammation was similar relative to HFD controls. Weight cycling did not significantly affect blood glucose or plasma insulin levels yet significantly reduced plasma free fatty acid and alanine transaminase/aspartate transaminase levels. Hepatic macrovesicular steatosis was similar and microvesicular steatosis tended to be increased upon weight cycling. Weight cycling resulted in a robust decrease in hepatic inflammation compared to HFD controls while hepatic fibrosis and atherosclerosis development were not affected. These results argue against the postulate that repeated weight cycling leads to unfavorable metabolic effects, when compared to a continuous unhealthy lifestyle, and in fact revealed beneficial effects on hepatic inflammation, an important hallmark of non-alcoholic steatohepatitis.

Histomorphological stratification of blubber of three dolphin species from sub-tropical waters

Blubber is a highly specialised and dynamic tissue unique to marine mammals and presents a reflection of the individuals' nutrition, environment, and life history traits. Few studies have investigated the histomorphology of cetacean blubber in sub-tropical environments. The aim of this study was to investigate the blubber histomorphology of three different dolphin species off the sub-tropical KwaZulu-Natal coast, South Africa, using adipocyte cell size, number and density. Blubber tissue samples from the saddle area of 43 incidentally bycaught animals (4 Sousa plumbea, 36 Tursiops aduncus and 3 Delphinus delphis) were used to compare cell parameters between blubber layers. Samples were divided into upper third (corresponding to the superficial layer closest to the epidermis), middle third, and lower third (corresponding to the deep layer). For T. aduncus, factors potentially affecting blubber histomorphology, such as sex, age class and season, were also assessed. Our results showed that no stratification was present in S. plumbea, which could be ascribed to the species' warmer inshore habitat, large body size and apparent lower mobility. For T. aduncus and D. capensis, however, blubber stratification was determined, characterised by a gradual transition of cell size, number and density between layers rather than clearly defined layers. Significant differences in adipocyte cell number and density were found for different sexes and age classes of T. aduncus. However, there were no significant differences between seasons, which was attributed to the small temperature differences between seasons. This study represents the first investigation on odontocete blubber histomorphology in subtropical waters. It is recommended that future studies investigate blubber lipid content, while also taking into consideration the reproductive status of the females and the temperature range of their study area. It is hoped that our results, in conjunction with histopathology and other health indicators, could assist in assessing health and body condition. This article is protected by copyright. All rights reserved.

Fat Cell Size: Measurement Methods, Pathophysiological Origins, and Relationships With Metabolic Dysregulations

The obesity pandemic increasingly causes morbidity and mortality from type 2 diabetes, cardiovascular diseases and many other chronic diseases. Fat cell size (FCS) predicts numerous obesity-related complications such as lipid dysmetabolism, ectopic fat accumulation, insulin resistance, and cardiovascular disorders. Nevertheless, the scarcity of systematic literature reviews on this subject is compounded by the use of different methods by which FCS measurements are determined and reported. In this paper, we provide a systematic review of the current literature on the relationship between adipocyte hypertrophy and obesity-related glucose and lipid dysmetabolism, ectopic fat accumulation, and cardiovascular disorders. We also review the numerous mechanistic origins of adipocyte hypertrophy and its relationship with metabolic dysregulation, including changes in adipogenesis, cell senescence, collagen deposition, systemic inflammation, adipokine secretion, and energy balance. To quantify the effect of different FCS measurement methods, we performed statistical analyses across published data while controlling for body mass index, age, and sex.

Overfeeding-induced weight gain elicits decreases in sex hormone-binding globulin in healthy males-Implications for body fat distribution

OBJECTIVE

Obesity and upper-body fat elevates cardiometabolic risk. However, mechanisms predisposing to upper-body fat accumulation are not completely understood. In males, low testosterone (T) frequently associates with obesity, and estrogen deficiency may contribute to upper-body adiposity. This study examines the effects of overfeeding-induced weight gain on changes in gonadal hormones in healthy males and its association with regional fat depots.

METHODS

Twenty-five males (age: 29.7 ± 6.9 years; BMI: 24.7 ± 3.1 kg/m2 ) were overfed for 8 weeks to gain approximately 5% body weight. Changes in total and regional fat depots were assessed using dual-energy x-ray absorptiometry and abdominal computed tomography scans. Circulating T, estrone (E1), 17-β estradiol (E2), and sex hormone-binding globulin (SHBG) concentrations were measured at baseline and after weight gain.

RESULTS

Overfeeding resulted in 3.8 (3.3, 4.9) kg weight gain with increased total body fat. Weight gain did not alter circulating T (p = 0.82), E1 (p = 0.52), or E2 (p = 0.28). However, SHBG decreased (p = 0.04) along with consequent increases in T/SHBG (p = 0.02) and E2/SHBG (p = 0.03) ratios. Importantly, baseline E2/SHBG ratio was inversely associated with increases in upper-body fat mass (ρ = -0.43, p = 0.03).

CONCLUSIONS

Modest weight gain does not alter circulating gonadal hormones in males but may increase bioavailability of T and E2 via decreases in SHBG. The association between baseline E2/SHBG and regional fat mass suggests that higher levels of bioavailable E2 may protect from upper-body fat accumulation during overfeeding-induced modest weight gain in healthy males. Our study suggests a complex relationship between adipose tissue, gonadal hormones, and fat accumulation in males.

Stress Management as an Effective Complementary Therapeutic Strategy for Weight Loss in Children and Adolescents with Obesity: A Systematic Review of Randomized Controlled Trials

Lifestyle intervention programs, including mindfulness and stress management/emotional control training techniques have been infrequently studied in children. The aim of this systematic review was to assess whether implementing stress management/emotional control training strategies in the context of a body weight loss program in children and adolescents is associated with improved body weight outcome in this age group. A systematic literature search was conducted to identify relevant studies published before 31 December 2020 in the following databases: Medline (PubMed), Scopus, and Cochrane Central Registry of Controlled Trials. Only randomized clinical trials (RCTs) on mindfulness or stress management in children and adolescents with obesity were included in this systematic review. Six RCTs fulfilled the study inclusion criteria and included intervention (112 subjects) and control (137 subjects) groups. The interventions used were Mindfulness-Based Stress Reduction therapy for 8 weeks (three studies), a mindfulness-based group program for adolescents (one study), and Mindful Eating Intervention for 6 weeks (one study) and 10 weeks (one study). The intervention group demonstrated reduced adiposity markers as compared to controls in four of the six included studies. The presented studies support the hypothesis that a structured, mindfulness-based intervention program may lead to a decrease in the biomarkers of obesity.

Change in abdominal, but not femoral subcutaneous fat CT-radiodensity is associated with improved metabolic profile after bariatric surgery

BACKGROUND AND AIMS

Computed tomography (CT)-derived adipose tissue radiodensity represents a potential noninvasive surrogate marker for lipid deposition and obesity-related metabolic disease risk. We studied the effects of bariatric surgery on CT-derived adipose radiodensities in abdominal and femoral areas and their relationships to circulating metabolites in morbidly obese patients.

METHODS AND RESULTS

We examined 23 morbidly obese women who underwent CT imaging before and 6 months after bariatric surgery. Fifteen healthy non-obese women served as controls. Radiodensities of the abdominal subcutaneous (SAT) and visceral adipose tissue (VAT), and the femoral SAT, adipose tissue masses were measured in all participants. Circulating metabolites were measured by NMR. At baseline, radiodensities of abdominal fat depots were lower in the obese patients as compared to the controls. Surprisingly, radiodensity of femoral SAT was higher in the obese as compared to the controls. In the abdominal SAT depot, radiodensity strongly correlated with SAT mass (r = -0.72, p < 0.001). After surgery, the radiodensities of abdominal fat increased significantly (both p < 0.01), while femoral SAT radiodensity remained unchanged. Circulating ApoB/ApoA-I, leucine, valine, and GlycA decreased, while glycine levels significantly increased as compared to pre-surgical values (all p < 0.05). The increase in abdominal fat radiodensity correlated negatively with the decreased levels of ApoB/ApoA-I ratio, leucine and GlycA (all p < 0.05). The increase in abdominal SAT density was significantly correlated with the decrease in the fat depot mass (r = -0.66, p = 0.002).

CONCLUSION

Higher lipid content in abdominal fat depots, and lower content in femoral subcutaneous fat, constitute prominent pathophysiological features in morbid obesity. Further studies are needed to clarify the role of non-abdominal subcutaneous fat in the pathogenesis of obesity.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01373892.

Effects of a Hypercaloric and Hypocaloric Diet on Insulin-Induced Microvascular Recruitment, Glucose Uptake, and Lipolysis in Healthy Lean Men

OBJECTIVE

In mice fed a high-fat diet, impairment of insulin signaling in endothelium is an early phenomenon that precedes decreased insulin sensitivity of skeletal muscle, adipose tissue, and liver. We assessed in humans whether short-term overfeeding affects insulin-induced microvascular recruitment in skeletal muscle and adipose tissue before changes occur in glucose uptake and lipolysis. Approach and Results: Fifteen healthy males underwent a hypercaloric and subsequent hypocaloric diet intervention. Before, during, and after the hypercaloric diet, and upon return to baseline weight, all participants underwent (1) a hyperinsulinemic-euglycemic clamp to determine insulin-induced glucose uptake and suppression of lipolysis (2) contrast-enhanced ultrasonography to measure insulin-induced microvascular recruitment in skeletal muscle and adipose tissue. In addition, we assessed insulin-induced vasodilation of isolated skeletal muscle resistance arteries by pressure myography after the hypercaloric diet in study participants and controls (n=5). The hypercaloric diet increased body weight (3.5 kg; P<0.001) and fat percentage (3.5%; P<0.001) but did not affect glucose uptake nor lipolysis. The hypercaloric diet increased adipose tissue microvascular recruitment (P=0.041) and decreased the ratio between skeletal muscle and adipose tissue microvascular blood volume during hyperinsulinemia (P=0.019). Insulin-induced vasodilation of isolated skeletal muscle arterioles was significantly lower in participants compared with controls (P<0.001). The hypocaloric diet reversed all of these changes, except the increase in adipose tissue microvascular recruitment.

CONCLUSIONS

In lean men, short-term overfeeding reduces insulin-induced vasodilation of skeletal muscle resistance arteries and shifts the distribution of tissue perfusion during hyperinsulinemia from skeletal muscle to adipose tissue without affecting glucose uptake and lipolysis. Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02628301.

Effects of a Hypocaloric, Nutritionally Complete, Higher Protein Meal Plan on Regional Body Fat and Cardiometabolic Biomarkers in Older Adults with Obesity

BACKGROUND

Whether improvements in cardiometabolic health following weight loss (WL) are associated with changes in regional body fat distribution (gluteal vs. -android) is not well documented.

METHODS

Older (age: 70 ± 4 years; mean ± SD) adults with obesity were randomized to a 6-month WL program (WL; n = 47), accomplished using a hypocaloric, nutritionally complete, higher protein -(targeting ≥1.0 g/kg/day) meal plan, or a weight stability (WS; n = 49) program. Android, gynoid, visceral, and subcutaneous abdominal fat masses (via dual energy X-ray absorptiometry ) and fasting glucose and lipid profiles were assessed at baseline and 6 months.

RESULTS

The WL group lost more body weight (WL: -8.6% vs. WS: -1.7%, p < 0.01), resulting in a reduction in fat mass at each region only following WL (all p < 0.05). The decline in the ratio of android/gynoid fat mass also was significant only following WL, resulting in greater declines than WS (mean [95% CI]; WL: -0.026 [-0.040 to -0.011] vs. WS: 0.003 [-0.012 to 0.019] g, p < 0.01). The change in the ratio of visceral/subcutaneous abdominal fat mass was not significant in either group and did not differ between groups (WL: 0.65 [-0.38 to 1.68] vs. WS: 0.05 [-1.00 to 1.10] g, p = 0.42). In general, the improvements in glucose and lipid profiles were associated with declines in fat mass at the gynoid and android regions (r's = 0.20-0.42, all p < 0.05), particularly the visceral depot but not the ratios.

CONCLUSION

WL achieved via a hypocaloric, nutritionally complete, higher protein meal plan is effective in reducing body fat in the android, gynoid, and visceral depots, which relate to cardiometabolic improvements.

Cytometric analysis of adipose tissue reveals increments of adipocyte progenitor cells after weight loss induced by bariatric surgery

Obesity-related comorbidities are, in large part, originated from the dysfunction of adipose tissue. Most of them revert after the normalization of body mass. Adipose tissue is essentially occupied by adipocytes. However, different populations of immunological cells and adipocyte precursor cells (AdPCs) are the main cellular components of tissue. During obesity, body fat depots acquire a low-level chronic inflammation and adipocytes increase in number and volume. Conversely, weight loss improves the inflammatory phenotype of adipose tissue immune cells and reduces the volume of adipocytes. Nevertheless, very little is known about the evolution of the human AdPCs reservoir. We have developed a flow cytometry-based methodology to simultaneously quantify the main cell populations of adipose tissue. Starting from this technical approach, we have studied human adipose tissue samples (visceral and subcutaneous) obtained at two different physiological situations: at morbid obesity and after bariatric surgery-induced weight loss. We report a considerable increase of the AdPCs reservoir after losing weight and several changes in the immune cells populations of adipose tissue (mast cells increase, neutrophils decrease and macrophages switch phenotype). No changes were observed for T-lymphocytes, which are discussed in the context of recent findings.

Adult weight change in relation to visceral fat and liver fat at middle age: The Netherlands epidemiology of obesity study

OBJECTIVE

We aimed to investigate the associations between weight change during adulthood and the amount of abdominal subcutaneous fat, visceral fat, and liver fat at middle age.

METHODS

The Netherlands Epidemiology of Obesity (NEO) study is a population-based cohort of 6671 middle-aged men and women. We calculated the percentage of weight change during adulthood based on body weight at middle age and recalled body weight at age 20. Abdominal subcutaneous and visceral adipose tissue were assessed by magnetic resonance imaging (MRI), in addition to hepatic triglyceride content by ¹H-MR spectroscopy in a random subgroup (maximum of n = 2580). With multivariable linear regression analysis, we examined the associations between categories of adult weight change, body mass index (BMI) at age 20 and measures of abdominal adiposity at middle age, adjusted for age, sex, ethnicity, lifestyle factors, menopausal status, parity, use of medication and total body fat at middle age.

RESULTS

In 2399 participants (54% women), individuals who gained more than 50% of body weight during adulthood had 1.96 (95% CI: 1.64; 2.33) times more visceral adipose tissue at middle age and 2.39 (95% CI: 1.70, 3.36) times more hepatic triglyceride content than weight maintainers (weight change between -5% and 5%). Associations with abdominal subcutaneous adipose tissue were weaker: participants who gained more than 50% of their body weight had 1.54 (95% CI: 1.38, 1.72) times more abdominal subcutaneous adipose tissue compared with weight maintainers.

CONCLUSIONS

In this population-based study, adult weight gain was associated with relatively more visceral adipose tissue and hepatic triglyceride content at middle age than abdominal subcutaneous adipose tissue. Overall, our study suggests that weight maintenance during adulthood plays an important role in limiting excess visceral adipose tissue and hepatic triglyceride content at middle age.

Experimental Weight Gain Increases Ambulatory Blood Pressure in Healthy Subjects: Implications of Visceral Fat Accumulation

OBJECTIVE

To examine whether experimentally induced weight gain raises ambulatory blood pressure (BP) in healthy subjects and identify any relationship between changes in BP and changes in regional fat distribution.

PATIENTS AND METHODS

Twenty-six normal weight subjects were randomized to 8 weeks of weight gain through overfeeding (n=16; age, 30.4±6.6 years) or to weight maintenance (controls; n=10; age, 27.1±7.7 years) between July 2004 and August 2010. Measures of body composition via dual energy X-ray absorptiometry and computed tomography, circulating biomarkers, and 24-hour ambulatory BP were obtained at baseline and after the 8-week experimental phase.

RESULTS

Overfeeding resulted in 3.7 kg (95% CI, 2.9-4.5) increase in body weight in weight gainers, with increments in total (46.2 cm²; 95% CI, 27.6-64.9), visceral (13.8 cm²; 95% CI, 5.8-21.9), and subcutaneous fat (32.4 cm²; 95% CI, 13.5-51.3). No changes occurred in the maintenance group. Increases in 24-hour systolic BP (4 mm Hg; 95% CI, 1.6-6.3), mean BP (1.7 mm Hg; 95% CI, 0.3-3.3), and pulse pressure (2.8 mm Hg; 95% CI, 1.1-4.4) were evident after weight gain in the experimental group, whereas BP remained unchanged in controls. Changes in mean BP correlated only with changes in visceral fat (ρ=0.45; P=.02), but not with changes in other body composition measures.

CONCLUSION

Modest weight gain causes elevation in 24-hour BP in healthy subjects. The association between increased BP and abdominal visceral fat accumulation suggests that visceral deposition of adipose tissue may contribute specifically to the enhanced risk of hypertension associated with weight gain.

Fatty Acid Metabolic Remodeling During Type 2 Diabetes Remission After Bariatric Surgery

Hypertrophic remodeling of white adipose tissues is associated with overexposure of lean organs to circulating triglycerides (TGs) and nonesterified fatty acids (NEFAs), ultimately leading to insulin resistance. Bariatric surgery promotes type 2 diabetes (T2D) remission through a succession of weight loss-dependent and -independent mechanisms. However, the longitudinal contribution of adipocyte size reduction and fatty acid metabolic handling remain unknown. Here we show that severely obese participants with T2D display hypertriglyceridemia and excessive systemic lipolysis during intravenous lipid overload. Three days after biliopancreatic diversion with duodenal switch (DS), whole-body glycerol turnover was normalized and associated with lower HOMA-insulin resistance index. A mean excess weight loss of 84% was achieved 12 months after DS. The smaller subcutaneous adipocyte size predicted better glycemic control in T2D. TG disposal and acylcarnitine production during lipid overload, along with muscle insulin sensitivity, improved with weight loss. Nevertheless, systemic NEFA fluxes and NEFA spillover remained similar, suggesting that increased NEFA storage capacity per volume of adipose tissue exactly compensated for the decrease in fat mass during weight loss. In conclusion, T2D remission after DS is mainly associated with greater circulating TG disposal, lower systemic lipolysis, and better fatty acid handling by lean tissues.

Effects of Weight Loss with and without Exercise on Regional Body Fat Distribution in Postmenopausal Women

BACKGROUND/AIMS

The purpose was to determine whether lifestyle interventions have different effects on regional fat in women with normal glucose tolerance vs. impaired glucose tolerance (NGT vs. IGT).

METHODS

Changes in glucose metabolism (2-h oral glucose-tolerance tests), android to gynoid fat mass ratio (dual energy X-ray absorptiometry [DXA]), visceral to subcutaneous abdominal fat area ratio (CT), and abdominal to gluteal subcutaneous fat cell weight (FCW; adipose tissue biopsies) were determined in 60 overweight postmenopausal women (45-80 years) following 6 months of weight loss alone (WL; n = 28) or with aerobic exercise (AEX + WL; n = 32).

RESULTS

The interventions led to ∼8% decrease in weight, but only the AEX + WL group improved fitness (↑11% in VO2max) and reduced the android-to-gynoid fat mass ratio (↓5%; p < 0.05). Both NGT and IGT groups reduced visceral and subcutaneous abdominal fat areas and abdominal and gluteal FCWs, which related to improvements in homeostatic model assessment (r = 0.34-0.42) and 2-h glucose (r = 0.34-0.35), respectively (p < 0.05). The decline in FCW was 2× greater in women with IGT following WL (p < 0.05). The ratios of abdominal-to-gluteal FCW did not change following either intervention.

CONCLUSIONS

The mechanisms by which WL with and without exercise impact regional fat loss should be explored as reductions in abdominal fat area and subcutaneous FCW appear to influence glucose metabolism. This is a work of the U.S. Government and is not subject to copyright protection in the United States. Foreign copyrights may apply. Published by S. Karger AG, Basel.

Factors associated with adipocyte size reduction after weight loss interventions for overweight and obesity: a systematic review and meta-regression

AIMS

Enlarged adipocytes are a prime feature of adipose tissue dysfunction, and may be an appropriate target to decrease disease risk in obesity. We aimed to assess the change in adipocyte size in response to lifestyle and surgical weight loss interventions for overweight or obesity; and to explore whether certain participant and intervention characteristics influence this response.

METHODS

We systematically searched MEDLINE, EMBASE, CINAHL and Cochrane electronic databases to identify weight loss studies that quantified adipocyte size before and after the intervention. Using meta-regression analysis, we assessed the independent effects of weight loss, age, sex, adipocyte region, and intervention type (surgical vs. lifestyle) on adipocyte size reduction. We repeated the model as a sensitivity analysis including only the lifestyle interventions.

RESULTS

Thirty-five studies met our eligibility criteria. In our main model, every 1.0% weight loss was associated with a 0.64% reduction in adipocyte size (p=0.003); and adipocytes from the upper body decreased 5% more in size than those in the lower body (p=0.009). These relationships were no longer significant when focusing only on lifestyle interventions. Moreover, age, sex and intervention type did not independently affect adipocyte size reduction in either model.

CONCLUSIONS

Weight loss in obese individuals is consistently associated with a decrease in adipocyte size that is more pronounced in upper-body adipocytes. It remains to be clarified how biological differences and intervention characteristics influence this relationship, and whether it corresponds with reductions in other aspects of adipose tissue dysfunction and disease risk.

Metabolic dysfunction following weight cycling in male mice

Background

Combatting over-weight or obesity can lead to large fluctuations in an individual’s body weight, often referred to as weight cycling or “yo-yo” dieting. Current evidence regarding the potentially damaging effects of these changes is conflicting.

Methods

Here, we assess the metabolic effects of weight cycling in a murine model, comprising three dietary switches to normal or high fat diets at 6 week intervals; male C57BL/6 mice were fed either a control (C) or high fat (F) diet for 6 weeks (n=140/group). C and F groups were then either maintained on their initial diet (CC and FF respectively) or switched to a high fat (CF) or control (FC) diet (n=35/group). For the final 6 week interval, CC and CF groups were returned to the control diet (CCC and CFC groups) while FC and FF groups were placed on a high fat diet (FCF and FFF) (n=28/group).

Results

For the majority of metabolic outcomes changes aligned with dietary switches; however assessment of neuropeptides and receptors involved in appetite regulation and reward signalling pathways reveal variable patterns of expression. Furthermore, we demonstrate that multiple cycling events leads to a significant increase in internal fat deposition, even when compared to animals maintained on a high fat diet (Internal Fat: FCF: 7.4 ± 0.2g vs. FFF: 5.6 ± 0.2g; p<0.01).

Conclusions

Increased internal adipose tissue is strongly linked to the development of metabolic syndrome associated conditions such as type 2 diabetes, cardiovascular disease and hypertension. While further work will be required to elucidate the mechanisms underlying the neuronal control of energy homeostasis, these studies provide a causative link between weight cycling and adverse health.

Differential effects of leptin on adiponectin expression with weight gain versus obesity

Background/Objective

Adiponectin exerts beneficial effects by reducing inflammation, and improving lipid metabolism and insulin-sensitivity. Although adiponectin is lower in obese individuals, whether weight gain reduces adiponectin expression in humans is controversial. We sought to investigate the role of weight gain, and consequent changes in leptin, on altering adiponectin expression in humans.

Methods/Results

Forty four normal-weight healthy subjects were recruited (mean age 29 years; 14 women) and randomized to either gain 5% of body weight by 8-weeks of overfeeding (n=34) or maintain weight (n=10). Modest weight gain of 3.8 ± 1.2 kg resulted in increased adiponectin (p=0.03) while weight maintenance resulted in no changes in adiponectin. Further, changes in adiponectin correlated positively with changes in leptin (p=0.0085). In-vitro experiments using differentiated human white preadipocytes showed that leptin increased adiponectin mRNA and protein expression, while a leptin-antagonist had opposite effects. To understand the role of leptin in established obesity, we compared adipose tissue samples obtained from normal weight versus obese subjects. We noted, first, that leptin activated cellular signaling pathways and increased adiponectin mRNA in adipose tissue from normal-weight participants, but did not do so in adipose tissue from obese participants; and second, that obese subjects had increased caveolin-1 expression, which attenuates leptin-dependent increases in adiponectin.

Conclusions

Modest weight gain in healthy individuals is associated with increases in adiponectin, which correlate positively with changes in leptin. In-vitro, leptin induces adiponectin expression which is attenuated by increased caveolin-1 expression. Additionally, adipose tissue from obese subjects shows increased caveolin-1 expression, and impaired leptin signaling. This leptin signal impairment may prevent concordant increases in adiponectin in obese subjects despite their high levels of leptin. Therefore, impaired leptin signaling may contribute to low adiponectin expression in obesity and may provide a target for increasing adiponectin expression, hence improving insulin sensitivity and cardio-metabolic profile in obesity.

Change in knee contact force with simulated change in body weight

The relationship between obesity, weight gain and progression of knee osteoarthritis is well supported, suggesting that excessive joint loading may be a mechanism responsible for cartilage deterioration. Examining the influence of weight gain on joint compressive forces is difficult, as both muscles and ground reaction forces can have a significant impact on the forces experienced during gait. While previous studies have examined the relationship between body weight and knee forces, these studies have used models that were not validated using experimental data. Therefore, the objective of this study was to evaluate the relationship between changes in body weight and changes in knee joint contact forces for an individual's gait pattern using musculoskeletal modeling that is validated against known internal compressive forces. Optimal weighting constants were determined for three subjects to generate valid predictions of knee contact forces (KCFs) using in vivo data collection with instrumented total knee arthroplasty. A total of five simulations per walking trial were generated for each subject, from 80% to 120% body weight in 10% increments, resulting in 50 total simulations. The change in peak KCF with respect to body weight was found to be constant and subject-specific, predominantly determined by the peak force during the baseline condition at 100% body weight. This relationship may be further altered by any change in kinematics or body mass distribution that may occur as a result of a change in body weight or exercise program.

The associations between cardiometabolic risk factors and visceral fat measured by a new dual-energy X-ray absorptiometry-derived method in lean healthy Caucasian women

Excess visceral adipose tissue (VAT) is associated with a cluster of metabolic abnormalities. A new dual-energy X-ray absorptiometry (DXA)-based VAT measurement approach, CoreScan™, computes VAT mass and volume within the android region of a total body DXA scan. However, there have been no reference values developed for this method. The objective of this study was to determine the normal reference ranges for DXA-derived VAT in young, healthy, premenopausal women. We also sought associations between VAT, blood lipids, glucose, insulin and insulin resistance. In 120 randomly selected, normal weight, Caucasian women aged 20-40 years, we measured body fat (BF), VAT and lean mass by DXA. We also assessed blood pressure, waist and hip circumference, waist-to-hip ratio, body mass index, fasting glucose, insulin, triglycerides (TG), and high- (HDL) and low-density lipoproteins. Insulin resistance was evaluated by the homeostasis model assessment (HOMA). VAT mass accounted for 0.37 ± 0.3 % of weight and 1.11 ± 0.72 % of BF. Mean VAT mass and volume were 235.9 ± 183 g (95 % CI 202.7-269.1) and 250.3 ± 194.5 cm(3) (95 % CI 215.1-285.4), respectively. Anthropometric indices moderately correlated with VAT. VAT significantly correlated with HDL (R = -0.193; P = 0.03), glucose (R = 0.252; P = 0.005) and HOMA (R = 0.184; P = 0.049). In this study, we provide normal values of VAT mass and volume measured by DXA and determined for healthy, normal weight, Caucasian women aged 20-40 years. Even in such strictly selected population VAT correlated positively with insulin resistance and inversely with HDL.

Short-term obesity results in detrimental metabolic and cardiovascular changes that may not be reversed with weight loss in an obese dog model

The time course of metabolic and cardiovascular changes with weight gain and subsequent weight loss has not been elucidated. The goal of the present study was to determine how weight gain, weight loss and altered body fat distribution affected metabolic and cardiovascular changes in an obese dog model. Testing was performed when the dogs were lean (scores 4-5 on a nine-point scale), after ad libitum feeding for 12 and 32 weeks to promote obesity (>5 score), and after weight loss. Measurements included serum glucose and insulin, plasma leptin, adiponectin and C-reactive protein, echocardiography, flow-mediated dilation and blood pressure. Body fat distribution was assessed by computed tomography. Fasting serum glucose concentrations increased significantly with obesity (P< 0·05). Heart rate increased by 22 (SE 5) bpm after 12 weeks of obesity (P= 0·003). Systolic left ventricular free wall thickness increased after 12 weeks of obesity (P= 0·002), but decreased after weight loss compared with that observed in the lean phase (P= 0·03). Ventricular free wall thickness was more strongly correlated with visceral fat (r 0·6, P= 0·001) than with total body fat (r 0·4, P= 0·03) and was not significantly correlated with subcutaneous body fat (r 0·3, P= 0·1). The present study provides evidence that metabolic and cardiovascular alterations occur within only 12 weeks of obesity in an obese dog model and are strongly predicted by visceral fat. These results emphasise the importance of obesity prevention, as weight loss did not result in the return of all metabolic indicators to their normal levels. Moreover, systolic cardiac muscle thickness was reduced after weight loss compared with the pre-obesity levels, suggesting possible acute adverse cardiovascular effects.

The obesogen tributyltin

The obesogen hypothesis postulates the role of environmental chemical pollutants that disrupt homeostatic controls and adaptive mechanisms to promote adipose-dependent weight gain leading to obesity and metabolic syndrome complications. One of the most direct molecular mechanisms for coupling environmental chemical exposures to perturbed physiology invokes pollutants mimicking endogenous endocrine hormones or bioactive dietary signaling metabolites that serve as nuclear receptor ligands. The organotin pollutant tributyltin can exert toxicity through multiple mechanisms but most recently has been shown to bind, activate, and mediate RXR-PPARγ transcriptional regulation central to lipid metabolism and adipocyte biology. Data in support of long-term obesogenic effects on whole body adipose tissue are also reported. Organotins represent an important model test system for evaluating the impact and epidemiological significance of chemical insults as contributing factors for obesity and human metabolic health.

One day of mixed meal overfeeding reduces hepatic insulin sensitivity and increases VLDL particle but not VLDL-triglyceride secretion in overweight and obese men

CONTEXT

The exact mechanisms responsible for increased plasma triglyceride (TG) concentration in obese people are unclear, and it is not known whether excess energy intake per se is involved in the pathophysiology of this abnormality.

OBJECTIVE

The purpose of our study was to examine how excess energy intake from a balanced diet for 1 day affects very-low-density lipoprotein (VLDL)-TG kinetics and its putative regulators hepatic insulin sensitivity and plasma free fatty acid availability.

SUBJECTS AND DESIGN

We used stable isotope-labeled tracer methods to evaluate glucose and lipid kinetics in 8 overweight and obese men (age, 38 ± 3 years; body mass index, 33.7 ± 1.7 kg/m(2); means ± SEM) on 2 occasions (randomized crossover design): once, the day after they consumed a balanced diet that provided an amount of energy that matched their energy expenditure, and another time, the day after they consumed a balanced diet that provided 30% excess calories. Eight healthy, lean men (34 ± 1 years; 22.5 ± 0.6 kg/m(2)) were studied under isocaloric conditions only to provide a reference for normal lipid kinetics.

RESULTS

VLDL-TG and VLDL-apolipoprotein B-100 (apoB-100) concentrations and secretion rates were significantly greater (P < .01) in overweight/obese compared with lean men. Hypercaloric, compared with isocaloric, feeding in overweight/obese men increased glucose rate of appearance in plasma (904 ± 21 vs 873 ± 26 μmol/min), the hepatic insulin resistance index (10.9 ± 2.2 vs 8.3 ± 1.8), and VLDL-apoB-100 concentration and secretion rate (1.91 ± 0.24 vs. 1.53 ± 0.13 nmol/min), whereas VLDL-apoB-100 plasma clearance rate, VLDL-TG secretion and plasma clearance rates, and free fatty acid rate of appearance in plasma were not affected by overfeeding.

CONCLUSION

One day of moderate overfeeding (30% excess energy intake) stimulates hepatic glucose and VLDL-apo B-100 secretion rates but has no effect on hepatic and adipose tissue fatty acid metabolism in overweight/obese men.

Biological mechanisms that promote weight regain following weight loss in obese humans

Weight loss dieting remains the treatment of choice for the vast majority of obese individuals, despite the limited long-term success of behavioral weight loss interventions. The reasons for the near universal unsustainability of behavioral weight loss in [formerly] obese individuals have not been fully elucidated, relegating researchers to making educated guesses about how to improve obesity treatment, as opposed to developing interventions targeting the causes of weight regain. This article discusses research on several factors that may contribute to weight regain following weight loss achieved through behavioral interventions, including adipose cellularity, endocrine function, energy metabolism, neural responsivity, and addiction-like neural mechanisms. All of these mechanisms are engaged prior to weight loss, suggesting that these so called "anti-starvation" mechanisms are activated via reductions in energy intake, rather than depletion of energy stores. Evidence suggests that these mechanisms are not necessarily part of a homeostatic feedback system designed to regulate body weight, or even anti-starvation mechanisms per se. Although they may have evolved to prevent starvation, they appear to be more accurately described as anti-weight loss mechanisms, engaged with caloric restriction irrespective of the adequacy of energy stores. It is hypothesized that these factors may combine to create a biological disposition that fosters the maintenance of an elevated body weight and works to restore the highest sustained body weight, thus precluding the long-term success of behavioral weight loss. It may be necessary to develop interventions that attenuate these biological mechanisms in order to achieve long-term weight reduction in obese individuals.

Mechanisms and metabolic implications of regional differences among fat depots

Fat distribution is closely linked to metabolic disease risk. Distribution varies with sex, genetic background, disease state, certain drugs and hormones, development, and aging. Preadipocyte replication and differentiation, developmental gene expression, susceptibility to apoptosis and cellular senescence, vascularity, inflammatory cell infiltration, and adipokine secretion vary among depots, as do fatty-acid handling and mechanisms of enlargement with positive-energy and loss with negative-energy balance. How interdepot differences in these molecular, cellular, and pathophysiological properties are related is incompletely understood. Whether fat redistribution causes metabolic disease or whether it is a marker of underlying processes that are primarily responsible is an open question.

Effect of weight loss and regain on adipose tissue distribution, composition of lean mass and resting energy expenditure in young overweight and obese adults

BACKGROUND

Although weight cycling is frequent in obese patients, the adverse consequences on body composition and an increased propensity to weight gain remain controversial.

OBJECTIVE

We investigated the effect of intentional weight loss and spontaneous regain on fat distribution, the composition of lean mass and resting energy expenditure (REE).

DESIGN

Weight regainers (≥ 30% of loss, n=27) and weight-stable subjects (within <± 20% of weight change, n=20) were selected from 103 overweight and obese subjects (body mass index 28-43 kg m(-2), 24-45 years) who passed a 13-week low-calorie diet intervention. REE and body composition (by densitometry and whole-body magnetic resonance imaging) were examined at baseline, after weight loss and at 6 months of follow-up.

RESULTS

Mean weight loss was -12.3 ± 3.3 kg in weight-stable subjects and -9.0 ± 4.3 kg in weight regainers (P<0.01). Weight regain was incomplete, accounting for 83 and 42% of weight loss in women and men. Regain in total fat and different adipose tissue depots was in proportion to weight regain except for a higher regain in adipose tissue of the extremities in women and a lower regain in extremity and visceral adipose tissue in men. In both genders, regain in skeletal muscle of the trunk lagged behind skeletal muscle regain at the extremities. In contrast to weight-stable subjects, weight regainers showed a reduced REE adjusted for changes in organ and tissue masses after weight loss (P<0.001).

CONCLUSION

Weight regain did not adversely affect body fat distribution. Weight loss-associated adaptations in REE may impair weight loss and contribute to weight regain.

Differences between adiposity indicators for predicting all-cause mortality in a representative sample of United States non-elderly adults

BACKGROUND

Adiposity predicts health outcomes, but this relationship could depend on population characteristics and adiposity indicator employed. In a representative sample of 11,437 US adults (National Health and Nutrition Examination Survey, 1988-1994, ages 18-64) we estimated associations with all-cause mortality for body mass index (BMI) and four abdominal adiposity indicators (waist circumference [WC], waist-to-height ratio [WHtR], waist-to-hip ratio [WHR], and waist-to-thigh ratio [WTR]). In a fasting subsample we considered the lipid accumulation product (LAP; [WC enlargement*triglycerides]).

METHODS AND FINDINGS

For each adiposity indicator we estimated linear and categorical mortality risks using sex-specific, proportional-hazards models adjusted for age, black ancestry, tobacco exposure, and socioeconomic position. There were 1,081 deaths through 2006. Using linear models we found little difference among indicators (adjusted hazard ratios [aHRs] per SD increase 1.2-1.4 for men, 1.3-1.5 for women). Using categorical models, men in adiposity midrange (quartiles 2+3; compared to quartile 1) were not at significantly increased risk (aHRs<1.1) unless assessed by WTR (aHR 1.4 [95%CI 1.0-1.9]). Women in adiposity midrange, however, tended toward elevated risk (aHRs 1.2-1.5), except for black women assessed by BMI, WC or WHtR (aHRs 0.7-0.8). Men or women in adiposity quartile 4 (compared to midrange) were generally at risk (aHRs>1.1), especially black men assessed by WTR (aHR 1.9 [1.4-2.6]) and black women by LAP (aHR 2.2 [1.4-3.5]). Quartile 4 of WC or WHtR carried no significant risk for diabetic persons (aHRs 0.7-1.1), but elevated risks for those without diabetes (aHRs>1.5). For both sexes, quartile 4 of LAP carried increased risks for tobacco-exposed persons (aHRs>1.6) but not for non-exposed (aHRs<1.0).

CONCLUSIONS

Predictions of mortality risk associated with top-quartile adiposity vary with the indicator used, sex, ancestry, and other characteristics. Interpretations of adiposity should consider how variation in the physiology and expandability of regional adipose-tissue depots impacts health.

Physical activity: an important adaptative mechanism for body-weight control

We review the current concepts about energy expenditure and evaluate the physical activity (PhA) in the context of this knowledge and the available literature. Regular PhA is correlated with low body weight and low body fat mass. The negative fat balance is probably secondary to this negative energy balance. Nonexercise activity thermogenesis (NEAT) and physical activity, that is crucial for weight control, may be important in the physiology of weight change. An intriguing doubt that remains unresolved is whether changes in nutrient intake or body composition secondarily affect the spontaneous physical activity.