Relationship of co-morbidities of obesity to weight loss and four-year weight maintenance/rebound

Central neural and endocrine mechanisms of non-exercise activity thermogenesis and their potential impact on obesity

The rise in obesity is associated with a decline in the amount of physical activity in which people engage. The energy expended through everyday non-exercise activity, called non-exercise activity thermogenesis (NEAT), has a considerable potential impact on energy balance and weight gain. Comparatively little attention has been paid to the central mechanisms of energy expenditure and how decreases in NEAT might contribute to obesity. In this review, we first examine the sensory and endocrine mechanisms through which energy availability and energy balance are detected that may influence NEAT. Second, we describe the neural pathways that integrate these signals. Lastly, we consider the effector mechanisms that modulate NEAT through the alteration of activity levels as well as through changes in the energy efficiency of movement. Systems that regulate NEAT according to energy balance may be linked to neural circuits that modulate sleep, addiction and the stress response. The neural and endocrine systems that control NEAT are potential targets for the treatment of obesity.

Weight regain in U.S. adults who experienced substantial weight loss, 1999-2002

BACKGROUND

Relatively few studies have focused on who is at risk for weight regain after weight loss and how to prevent it. The objectives of this study were to determine the prevalence and predictors of weight regain in U.S. adults who had experienced substantial weight loss.

METHODS

Data were analyzed from the 1999-2002 National Health and Nutrition Examination Survey (NHANES). This study examined U.S. adults aged 20-84 years who were overweight or obese at their maximum weight (body mass index >/=25) and had experienced substantial weight loss (weighed 10% less than their maximum weight 1 year before they were surveyed) (n=1310).

RESULTS

Compared to their weight 1 year ago, 7.6% had continued to lose weight (>5%), 58.9% had maintained their weight (within 5%), and 33.5% had regained weight (>5%). Factors associated with weight regain (vs weight maintenance or loss) included Mexican American ethnicity (versus non-Hispanic white) (odds ratio [OR]=2.0; 95% confidence interval [CI]=1.3-3.1), losing a greater percentage of maximum weight (>/=20% vs 10% to <15%) (OR=2.8; 95% CI=2.0-4.1), having fewer years since reaching maximum weight (2-5 years vs >10 years) (OR=2.1; 95% CI=1.2-3.7), reporting greater daily screen time (>/=4 hours vs 0-1 hour) (OR=2.0; 95% CI=1.3-3.2), and attempting to control weight (OR=1.8; 95% CI=1.1-3.0). Finally, weight regain was higher in those who were sedentary (OR=1.8; 95% CI=1.0-3.0) or not meeting public health recommendations for physical activity (OR=2.0; 95% CI=1.2-3.5).

CONCLUSIONS

How to achieve the skills necessary for long-term maintenance of weight loss in the context of an obesogenic environment remains a challenge.

Comparison of orlistat and sibutramine in an obesity management program: efficacy, compliance, and weight regain after noncompliance

To describe the comparative efficacy of orlistat and sibutramine in an obesity management program, with specific attention to compliance and weight regains after noncompliance. We prospectively evaluated 182 obese patients who were randomized to treatment with orlistat (n=98) or sibutramine (n=84) along with the diet and exercise prescriptions. Compliance (or compliant patient) was defined as adherence to scheduled visit times (at 3- month intervals) and following the prescribed drug regimen. A telephone survey was conducted in case of noncompliance. Significant body weights improvements were seen in both treatment groups. Patients lost a mean of 7.6+/-2.8% and 10.5+/-2.9% of initial body weights after a mean drug use of 8.8+/-5.7 and 8.3+/-3.7 months in the orlistat and sibutramine groups, respectively (p<0.05 vs. initial body weight). Patients in the sibutramine group lost more weight than the orlistat group (p<0.05). A total of 102 patients (56%) were compliant (53.1% in the orlistat group and 59.5% in the sibutramine group). Factors associated with compliance included weight reduction of more than 5% in the first 3 months and adherence to physical activity. Higher initial body weight, prior anti-obesity therapy, number of concurrent medications, and comorbidity were associated with noncompliance. Weight regains in noncompliant patient were a mean of 5.2+/-5.1 kg after a mean period of 9.2+/-4.2 months in the orlistat group, and a mean of 6.1+/-3.8 kg after a mean period of 9.1+/-3.9 months in the sibutramine group (p<0.05 vs. last visit for both groups, p>0.05 between groups). Both drugs in an obesity management program can achieve substantial weight loss. However, noncompliance and rebound weight regain after noncompliance are considerable problems.

Changes in multiple health outcomes at 12 and 24 weeks resulting from 12 weeks of exercise counseling with or without dietary counseling in obese adults

OBJECTIVE

We compared health outcomes in obese adults who underwent 12 wk of exercise counseling with or without dietary counseling, followed by 12 wk of observational monitoring.

METHODS

Ninety adults (77 women and 13 men; 42.6 +/- 6.0 y; body mass index, 31.5 +/- 2.8 kg/m(2)) were randomly assigned to exercise-only (EX) or diet-plus-exercise (DEX) groups and counseled weekly by exercise physiologists on a 12-wk walking program. DEX subjects were also counseled by dietitians on a hypocaloric diet (-500 kcal/d). From weeks 12 to 24, subjects were monitored but not counseled. At weeks 0, 12, and 24, data collection included body composition (air displacement plethysmography), fitness (maximum oxygen consumption, 3-min step-test, and timed mile), plasma lipids, weight loss efficacy (Weight Efficacy Life-Style Questionnaire), quality of life (Medical Outcomes Study Health Survey-Short Form 36), and mood (Profile of Mood States).

RESULTS

At 12 and 24 wk, weight and body mass index decreased in DEX subjects (both P < 0.05) but not in EX subjects. However, lean body mass increased significantly in EX (24 wk, P < 0.05) but not in DEX subjects. In both groups, fat mass decreased (P < 0.05 for EX subjects at 24 wk; P < 0.05 for DEX subjects at 12 and 24 wk) and waist circumference decreased (P < 0.05 for EX subjects at 12 and 24 wk; P < 0.05 for DEX subjects at 12 and 24 wk). At 12 and 24 wk, DEX subjects showed decreased levels of total plasma cholesterol and triacylglycerols (both P < 0.05) and improvements with regard to the Weight Efficacy Life-Style Questionnaire (P < 0.05), three domains of the Medical Outcomes Study Health Survey-Short Form 36 (all P < 0.05), and three domains of the Profile of Mood States (all P < 0.05) that were not seen in EX subjects.

CONCLUSIONS

Exercise counseling for 12 wk in obese adults improves some body composition indices that can be sustained over 12 wk of monitoring. The addition of dietary counseling increases improvements in body composition, lipid profiles, and several psychological parameters.

Obesity and hypertension: two epidemics or one?

The association between obesity and hypertension is well documented, although the exact nature of this relation remains unclear. Sympathetic nervous and renin-angiotensin-aldosterone system activation appear to play an important role in the sodium and water retention, rightward shift in the pressure-natriuresis, and blood pressure elevation observed in obese individuals. Visceral obesity and the ectopic deposition of adipose tissue may be important in the activation of these systems and in the target organ damage that ensues. Weight loss is critical in the effective management of obesity hypertension and the accompanying target organ damage, although recidivism rates are high. However, prevention of weight gain should be the major priority for combating hypertension and its consequences in the future. The present review will provide an overview of our understanding of the etiology, pathophysiology, and treatment of obesity hypertension. Our focus is on the state of knowledge in humans. The potential role of abdominal obesity is considered throughout our review. We refer to relevant animal literature for supportive evidence and where little or no data in humans are available.

Obesity and cardiovascular disease risk: research update

The obesity epidemic has reached unprecedented proportions in Western society. Evidence continues to accumulate that obesity is associated with significant morbidity and mortality and in particular that it is an independent risk factor for cardiovascular disease (CVD). The association of obesity with CVD and its risk factors, including hypertension, dyslipidemia, glucose intolerance, and impaired hemostasis is becoming more clearly understood. An increasing body of data indicates that risk factors tend to cluster in obese individuals and may act synergistically to increase these people's risk for CVD. Individuals with disproportionate visceral adiposity are at significantly greater risk for CVD. Adult weight gain also underlies the development of many risk factors and augments the risk of CVD. Physicians can play a vital and active role in the prevention and treatment of obesity and overweight and thereby reduce patients' CVD risk.

Weight-loss maintenance in overweight individuals one to five years following successful completion of a commercial weight loss program

OBJECTIVE

To determine weight loss maintenance among participants in a commercial weight loss program (Weight Watchers) who had reached their goal weights 1-5 y previously.

DESIGN

A national sample (n=1002) was surveyed by phone to obtain demographic and weight-related information. An oversample (n=258) was recruited and weighed in person to develop a correction factor for self-reported weights in the national sample.

RESULTS

Based on corrected weights, weight regain from 1 to 5 y following weight loss ranged between 31.5 and 76.5%. At 5 y, 19.4% were within 5 lb of goal weight, 42.6% maintained a loss of 5% or more, 18.8% maintained a loss of 10% or more, and 70.3% were below initial weight.

CONCLUSIONS

These results are not directly comparable to those obtained in clinical settings because of differences in the populations studied. Nonetheless, they suggest that the long-term prognosis for weight maintenance among individuals who reach goal weight in at least one commercial program is better than that suggested by existing research.

Do adaptive changes in metabolic rate favor weight regain in weight-reduced individuals? An examination of the set-point theory

BACKGROUND

Obese persons generally regain lost weight, suggesting that adaptive metabolic changes favor return to a preset weight.

OBJECTIVE

Our objective was to determine whether adaptive changes in resting metabolic rate (RMR) and thyroid hormones occur in weight-reduced persons, predisposing them to long-term weight gain.

DESIGN

Twenty-four overweight, postmenopausal women were studied at a clinical research center in four 10-d study phases: the overweight state (phase 1, energy balance; phase 2, 3350 kJ/d) and after reduction to a normal-weight state (phase 3, 3350 kJ/d; phase 4, energy balance). Weight-reduced women were matched with 24 never-overweight control subjects. After each study phase, assessments included RMR (by indirect calorimetry), body composition (by hydrostatic weighing), serum triiodothyronine (T(3)), and reverse T(3) (rT(3)). Body weight was measured 4 y later, without intervention.

RESULTS

Body composition-adjusted RMR and T(3):rT(3) fell during acute (phase 2) and chronic (phase 3) energy restriction (P: < 0.01), but returned to baseline in the normal-weight, energy-balanced state (phase 4; mean weight loss: 12.9 +/- 2.0 kg). RMR among weight-reduced women (4771 +/- 414 kJ/d) was not significantly different from that in control subjects (4955 +/- 414 kJ/d; P: = 0.14), and lower RMR did not predict greater 4-y weight regain (r = 0.27, NS).

CONCLUSIONS

Energy restriction produces a transient hypothyroid-hypometabolic state that normalizes on return to energy-balanced conditions. Failure to establish energy balance after weight loss gives the misleading impression that weight-reduced persons are energy conservative and predisposed to weight regain. Our findings do not provide evidence in support of adaptive metabolic changes as an explanation for the tendency of weight-reduced persons to regain weight.

Marked weight reduction lowers resting and exercise blood pressure in morbidly obese subjects

Obesity and high blood pressure (BP) often coexist. Weight reduction lowers resting BP but its effect on BP during exercise (a predictor of target organ damage) has not been evaluated. Blood pressure was measured at rest and during cycling, before and after weight reduction induced by gastric restriction. Nineteen subjects (4 male), 41 +/-2 (SEM) years of age and body mass index (BMI) of 43 +/- 0.9 kg/m2, were studied. On each occasion BP was measured at rest, at a steady state of 0 and 25 watts, at peak exercise and 1 min into recovery. Body weight was reduced by 28% +/- 6% and BMI decreased from 43.3 +/- 0.9 to 31.5 +/- 0.7 kg/m2 (P < .01). Both BP and heart rate, at rest and at all exercise intensities, were significantly lower after weight reduction. Resting BP decreased from 133 +/-4/87 +/- 3 mm Hg to 115 +/- 4/77 +/- 2 mm Hg (P < .001), and BP at peak exercise decreased from 181 +/- 8/98 +/- 4 to 162 +/- 6/83 +/- 5 mm Hg (P < .001). The change in resting systolic BP did not correlate with the change in body weight or with the change in heart rate, but it correlated with the baseline systolic BP (R = 0.61; P < .005). It is concluded that marked weight reduction reduces BP at rest and at all exercise intensities. Gastroplasty should be considered as an option in morbidly obese hypertensive patients who are not well controlled with conventional treatment, and who fail to lose or to maintain a reduced weight by calorie restriction alone.

Physical activity and energy balance

Energy expenditure rises above resting energy expenditure when physical activity is performed. The activity-induced energy expenditure varies with the muscle mass involved and the intensity at which the activity is performed: it ranges between 2 and 18 METs approximately. Differences in duration, frequency and intensity of physical activities may create considerable variations in total energy expenditure. The Physical Activity Level (= total energy expenditure divided by resting energy expenditure) varies between 1.2 and 2.2-2.5 in healthy adults. Increases in activity-induced energy expenditure have been shown to result in increases in total energy expenditure, which are usually greater than the increase in activity-induced energy expenditure itself. No evidence for increased spontaneous physical activity, measured by diary, interview or accelerometer, was found. However, this does not exclude increased physical activity that can not be measured by these methods. Part of the difference may also be explained by the post-exercise elevation of metabolic rate. If changes in the level of physical activity affect energy balance, this should result in changes in body mass or body composition. Modest decreases of body mass and fat mass are found in response to increases in physical activity, induced by exercise training, which are usually smaller than predicted from the increase in energy expenditure. This indicates that the training-induced increase in total energy expenditure is at least partly compensated for by an increase in energy intake. There is some evidence that the coupling between energy expenditure and energy intake is less at low levels of physical activity. Increasing the level of physical activity for weight loss may therefore be most effective in the most sedentary individuals.

Physical activity and low-fat diet: is it enough to maintain weight stability in the reduced-obese individual following weight loss by drug therapy and energy restriction?

OBJECTIVE

The anthropometric and physiological effects of a physical activity (PA) and a mildly energy-restricted low-fat diet (LFD) follow-up program after a long-term dietary restriction were studied in 12 men and 8 women.

RESEARCH METHODS AND PROCEDURES

The dietary restriction (approximately 700 kcal/day) was accompanied by a fenfluramine (60 mg/day) or placebo treatment for 15 weeks, whereas the mean duration of the PA-LFD follow-up was 18 weeks.

RESULTS

The long-term dietary restriction reduced body weight (-11.9 and -7.6 kg, p<.001), fat mass (FM) (-10.6 and -5.8 kg, p<0.01), resting metabolic rate (RMR) (-304 kcal/day, p<0.01 and -148 kcal/day, NS) in men and women, respectively. A decrease in fat-free mass (FFM) was also observed in women (-1.8 kg, p<0.05). The PA-LFD follow-up preserved weight stability at a reduced body weight and caused an additional significant decrease in FM for men (-3.4 kg, p<0.05). This part of the intervention also caused an increase in daily RMR for men (134 kcal/day, NS) to the point where this value no longer differed from the pre-energy restriction value. In contrast, RMR was further reduced in women (-200 kcal/day) to the point where it significantly differed from initial values (p<0.01). Resting seated heart rate was reduced by the PA-LFD follow-up in men leading it to differ significantly from both pre- and post-energy restriction values (-8.5 and -5.5 bpm, p<0.01).

DISCUSSION

In conclusion, these results suggest that a PA-LFD follow-up has the potential to permit body weight stability and may even accentuate fat loss in the reduced-obese state. Moreover, resting energy expenditure is increased under such conditions in men. These stimulating effects seem to be specific to energy metabolism since seated heart rate was either further reduced or remained stable in response to the PA-LFD follow-up.

Weight loss maintenance: determinants of long-term success

To analyse determinants of long-term weight maintenance we studied energy expenditure, dietary intake, eating behaviour and psychological symptoms of 9 women (SS, BMI = 26.6) who reached their ideal weight during 1985-86 and were still an average 16.2 kg below their original weight in 1993. Controls were 42 obese, non-reducing females (OC, BMI = 34.8). Dietary intake was calculated from four-day food records. Dietary restraint was assessed by the Three-Factor Eating Questionnaire (TFEQ) and symptoms of bulimia or binge eating by Bulimic Investigatory Test, Edinburgh (BITE). Physical exercise was estimated by open interviews, resting metabolic rate (RMR) by indirect calorimetry and body composition by bioelectrical impedance. Psychological characteristics were studied using the Defense Style Questionnaire (DSQ), Beck Depression Inventory (BDI) and Symptom Checklist (SCL-90). SS had lower RMR (1320 kcal vs. 1540 kcal, p = 0.004), lower daily energy intake (1208 kcal vs. 1525 kcal, p = 0.020) and higher scores for dietary restraint (14.6 vs. 8.4, p = 0.002) than OC. Restraint scores correlated negatively with energy intake and RMR in both groups, especially in SS (r = -0.75, p = 0.021 and r = -0.87, p = 0.002, respectively). Attempts to incorporate habitual physical activities to daily life (89% vs. 39%, p = 0.011) and weekly sports hobbies (67% vs. 13%, p = 0.002) were more often reported by SS. The scores of BITE, DSQ, BDI and SCL-90 were within normal range in both groups but SS had higher scores in most measures, especially for anxiety (16.4 vs. 14.3, p = 0.045). In conclusion, long-term maintenance of weight loss was associated with highly restrained eating, regular physical activity, and perhaps with increased anxiety.

Relation of left ventricular midwall function to cardiovascular risk factors and arterial structure and function

Left ventricular (LV) midwall shortening (MWS) is subnormal in relation to LV circumferential end-systolic stress (ESS) (ESS-corrected MWS) in many hypertensive patients with normal LV chamber function and predicts subsequent morbidity and mortality. However, little is known of the relations of LV midwall function to demographic and metabolic variables or to arterial geometry. Asymptomatic, unmedicated normotensive (n=366) or hypertensive (n=282) adults were assessed with echocardiography and carotid ultrasound. In normal adults, lower LV MWS and ESS-corrected MWS, an index of LV contractility, were related independently to high total peripheral resistance, high heart rate, and male gender (all P<.00001), lower serum HDL cholesterol (P=.001) and diastolic pressure (P=.003), and for ESS-corrected MWS only, arterial relative wall thickness (RWT, P=.03). Among hypertensive patients, lower values for both midwall function indices were associated independently with higher peripheral resistance (P<.00001), heart rate (P<.00005), body mass index (P<.01), and arterial RWT (P=.04), as well as male gender (P<.0002). In the entire population, lower LV MWS was independently related to higher peripheral resistance, heart rate (both P<.00001), body mass index (P=.0006) and arterial RWT (P=.009); male gender (P<.00001); and lower age (P=.004), diastolic pressure (P=.042), and systolic carotid artery expansion (P=.032). Lower ESS-corrected MWS in the entire population was independently associated with higher peripheral resistance and heart rate (both P<.00001), body mass index (P=.0006), arterial RWT (P=.004); male gender; and lower diastolic pressure (both P<.00001), age (P<.00005), arterial expansion in systole (P=.006), and serum HDL cholesterol levels (P=.04). Among a subset (n=60), ESS-corrected MWS was positively related to apolipoprotein A1 (P=.004) and negatively to hemoglobin A1c (P<.01). Thus, higher LV midwall function is associated with female gender and more favorable profiles of hemodynamics, metabolic pattern, and arterial structure and function.