The energetics of obesity

Although there is little argument about the state of energy imbalance that produces weight gain, there is considerable argument about the respective role of genetics, diet and physical activity in achieving obesity. In the USA, obesity has increased in the last decades despite a concomitant decrease in total energy and fat intake suggesting that there has been a dramatic drop in total energy expenditure. In this review, we investigated the respective role of resting metabolic rate, post-prandial thermogenesis, and activity energy expenditure in this lower energy output, and provided evidence that physical inactivity is the major contributor. Based on Jean Mayer original observation (Mayer et al., 1954), we hypothesize that there is a level of physical activity below which mechanisms of body mass regulation are impaired. The increasing prevalence of obesity may reflect the fact the majority of the population has fallen below such a level of physical activity. However, a causal relation between physical inactivity and obesity is still difficult to prove, probably because of the lack of longitudinal models to investigate the physiological consequences of inactivity and because the deleterious consequences of sedentary behaviors are essentially deduced from the benefits of exercise training. By using long term strict bed rest as a unique model of inactivity, we provide evidence that inactivity per se indeed disrupts fuel homeostasis and partitions post-absorptive and post-prandial fat use towards storage, thus promoting weight gain in the long term. More research is needed to investigate mechanisms and to determine the minimal physical activity our body has been engineered for by evolution.     

Physical activity and muscle function but not resting energy expenditure impact on weight gain

Understanding whether metabolic factors are predictive of weight gain is important for developing strategies for prevention of weight gain. Recent research has shown that sleeping and resting energy expenditure are not predictive of weight gain. However, exercise endurance, muscular strength, (31)P MRS muscle metabolic economy, and maximum oxygen uptake are independently related to weight gain. Activity-related energy expenditure and the time spent in physical activity are also related to weight gain, with low physical activity explaining approximately 77% of weight gain at 1 year. In addition, weight maintainers spend 80 minutes per day, whereas weight gainers spend less than 20 minutes per day in physical activity equivalent to an intensity of about 4 METS. It is proposed that strength, aerobic fitness, and physical activity are important factors for reducing the rate of weight gain. Although further research is required, these results are suggestive that weight maintenance programs will be more successful if some relatively high-intensity training is included to complement large amounts of low to moderate intense physical activity.     

Weight loss maintenance following a primary care intervention for low-income minority women

Although the primary care setting offers an innovative option for weight loss interventions, there is minimal research examining this type of intervention with low-income minority women. Further, there is a lack of research on the long-term effects of these programs. The purpose of this investigation was to examine the weight loss maintenance of low-income African-American women participating in a primary care weight management intervention. A randomized controlled trial was conducted with overweight and obese women (N = 144) enrolled at two primary care clinics. Women received a 6-month tailored weight loss intervention delivered by their primary care physician and completed follow-up assessments 9, 12, and 18 months following randomization. The weight loss maintenance of the tailored intervention was compared to a standard care comparison group. The weight loss of intervention participants (-1.52 +/- 3.72 kg) was significantly greater than that of standard care participants (0.61 +/- 3.37 kg) at month 9 (P = 0.01). However, there was no difference between the groups at the 12-month or 18-month follow-ups. Participants receiving a tailored weight loss intervention from their physician were able to maintain their modest weight loss up to 3-6 months following treatment. Women demonstrated weight regain at the 18-month follow-up assessment, suggesting that more intensive follow-up in the primary care setting may be needed to obtain successful long-term weight loss maintenance.     

Obesity reduction black intervention trial (ORBIT): six-month results

The Obesity Reduction Black Intervention Trial (ORBIT) is a randomized controlled trial designed to assess the efficacy of a culturally proficient 6-month weight loss intervention followed by a 1-year maintenance intervention. This article describes the results of the 6-month weight loss intervention. Two hundred thirteen obese black women aged 30-65 years were randomized to the intervention group or a general health control group. The intervention consisted of a 6-month culturally adapted weight loss program that targeted changes in diet and physical activity patterns. Weight, dietary intake, and physical activity were measured at baseline and 6 months. A total of 198 women (93%) completed both the baseline and postintervention assessments. Women in the intervention group lost significantly more weight than women in the control group (P < 0.001). However, weight change was variable within the intervention group, with a maximum weight loss of 19.4% of initial body weight and a maximum weight gain of 6.4% of initial body weight. Women in the intervention group also showed significant improvements in fruit intake (P < 0.01), Healthy Eating Index score (P < 0.001), and moderate (P = 0.05), and vigorous (P < 0.001) physical activity compared to women in the control group. This study demonstrates that a culturally adapted program can successfully promote weight loss in obese black women. However, average weight loss was relatively modest, and weight change varied widely within the intervention group. Further research is needed in order to develop programs that will allow more black women to achieve their weight loss goals..     

A combined healthy strategy for successful weight loss,weight maintenance and improvement of hepatic lipid metabolism

Obesity is critically related with the development of metabolic and pathophysiological alterations among which non-alcoholic fatty liver disease (NAFLD) is of especial relevance. Although there are numerous strategies to successfully treat obesity, the prevention of weight regain still remains challenging for individuals who have undergone weight loss programs. In such context, diet and physical activity are considered essential for the regulation of body weight and lipid metabolism. In this study, rats were fed a high-fat diet (HFD) to induce obesity and alterations in hepatic lipid metabolism. Obese rats were then treated with single or combined strategies of caloric restriction, physical exercise, and/or pharmacological treatment with an appetite suppressant, to lose weight, reverse the obesity-related alterations in hepatic morphology and lipid metabolism and maintain the beneficial effects of the interventions used. HFD induced excess body weight, hepatic steatosis, altered fatty acid profile, dysregulated gene expression of lipogenic and lipolytic enzymes, as well as plasma markers of liver damage, and modifications in liver antioxidant enzyme activity. Such alterations were ameliorated by caloric restriction in combination with a mixed training protocol and/or food-intake inhibitor administration during a weight loss intervention period of 3 weeks, and the beneficial effects remained after 6 weeks of weight maintenance, with some interesting interactions observed. In conclusion, weight loss strategies assayed were efficient at correcting the obesogenic action of a HFD and related alterations in hepatic functionality through different molecular mechanisms. The beneficial effects were also evident along the post-intervention maintenance period to avoid body weight regain.     

Longitudinal Relationship between Elapsed Time in the Action Stages of Change and Weight Loss

Objective: The objective of this study was to examine the longitudinal relationship between the elapsed time in the action and maintenance stages of change for multiple target behaviors and weight loss or gain. Research Methods and Procedures: The research design was a prospective cohort study of overweight and obese primary care patients randomized to an obesity management intervention based on the Transtheoretical Model and a chronic disease paradigm. The target behaviors included increased planned exercise and usual physical activity, decreased dietary fat, increased fruit and vegetable consumption, and increased dietary portion control. The participants were 329 middle‐aged men and women with elevated body mass indices recruited from 15 primary care practices in Northeastern Ohio; 28% of the participants were African Americans. The main outcomes were weight loss (5% or more) or weight gain (5% or more) after 18 or 24 months of follow‐up. Results: There were significant (p < 0.05) longitudinal relationships between the number of periods (0 to 4) in action or maintenance for each of the five target behaviors, or a composite score taken across the five target behaviors, and weight loss. In all cases, there was a significant (p < 0.05) stepped (graded) relationship between the time in action or maintenance and weight loss (or gain). Discussion: The data support the concept of applying the Transtheoretical Model to the problem of managing obesity in primary care settings. The remaining challenge is to identify those factors that reliably move patients into the action and maintenance stages for long periods.     

Avian research in the Caribbean: past contributions and current priorities

ABSTRACT The islands of the Caribbean contain habitat of critical importance to a large number of endemic and resident birds, as well as many overwintering Neotropical migrants, and they rank as a globally outstanding conservation priority ecoregion and biodiversity hotspot. Considerable research from the region has focused on the ecology of permanent resident species, and these studies have had particular significance for threatened species management, especially parrot biology and conservation, but also for tropical community ecology in general. Work by ornithologists in the Caribbean has been instrumental in improving our understanding of the ecology of overwintering Neotropical migrants and in developing long‐term monitoring programs. Although Caribbean‐based studies of birds have resulted in significant contributions in many important areas of ecological research, there is a great need for additional research. Especially needed are studies with application to the management of resident species, and studies of how bird populations may be affected by pathogens, parasites, plants, and other types of biotic interactions. Studies focusing on how bird species and populations are affected by global climate change, and cumulative, landscape‐level changes in land use are also needed. Along with additional research, scientists have an important role to play in building capacity to prepare the next generation of biologists in the region who will need to address mounting challenges related to biodiversity protection. As with many conservation efforts, funding is a critical need for almost all organizations and agencies involved in research, conservation action, and capacity building in the West Indies.     

Identification and correlates of weight loss in adolescents in a national sample

Objective: Little is known about behaviors associated with successful weight loss during adolescence. The first objective of the current study was to identify meaningful weight loss, weight maintenance, and weight gain in male and female adolescents. The second objective of this study was to apply these methods to U.S. adolescents from the National Health and Nutrition Survey 1999 to 2002 data and to identify factors associated with these weight change outcomes. Research Methods and Procedures: The current analyses include 1726 (female, 836; male, 890) 16‐ to 18‐year‐old adolescents who completed the questionnaire components and interview for either the 1999–2000 or the 2001–2002 National Health and Nutrition Survey study. Dietary intake, physical activity, and dieting attitudes were compared across the weight loss (L), maintain (M), and gain (G) groups in the entire sample and in a subset of adolescents who are overweight and at‐risk‐for‐overweight (≥85th percentile). Results: The tested method for identifying weight L, M, and G groups has both theoretical and statistical validity and, when applied to the sample, showed the expected direction of changes in weight. Results suggest that more overall physical activity, more vigorous exercise, and less sedentary activity are associated with being in the L group in both the full sample and the overweight and at‐risk‐for‐overweight sample. In addition, fewer teens in the L groups endorsed efforts at trying to lose weight, compared with the M and G groups. Discussion: This study provides a method to determine successful adolescent weight loss for researchers and provides useful concrete information about successful weight loss for clinicians and others who work with adolescents.     

Weight loss maintenance in severely obese adults after an intensive lifestyle intervention: 2- to 4-year follow-up

Objective: To evaluate the long‐term weight loss maintenance after 2 to 4 years in severely obese subjects after a lifestyle intervention at a weight loss camp in Denmark. Research Methods and Procedures: In a retrospective follow‐up study, we assessed weight loss after 21 weeks of treatment at a weight loss camp, weight loss maintenance after 2 to 4 years, and numbers of subjects with a weight loss maintenance of ≥10% of a total number of 435 severely obese adults participating in an intensive lifestyle intervention with a primary focus on physical activity. Results: We obtained follow‐up data of 249 subjects (180 women and 69 men) with an initial body weight of 142 ± 32 kg. After 21 weeks at the camp, the subjects had reduced their body weight with a mean of 21.9 ± 13 kg (corresponding to a 15% weight loss). The average weight loss maintenance was 5.3% at a follow‐up after 2 to 4 years, and 28.3% had maintained a weight loss above 10% after 4 years of follow‐up. Discussion: Weight loss camps are a relatively new commercial approach in treating severely obese subjects. However, the results demonstrate that even with a multidisciplinary intensive setting with focus on diet, exercise, and psychological counseling, only 28% had maintained a weight loss above 10% after 4 years. This emphasizes that obesity is a chronic condition that needs additional strategies after a weight loss intervention in the efforts to maintain a sufficient weight loss.     

Fatness, menarche, and female fertility

It is hypothesized that a particular ratio of fat to lean mass is required for menarche and the maintenance of regular menstrual cycles. Females who lose 10-15% of normal weight for height, equivalent to a loss of 1/3 of body fat, become amenorrheic, presumably due to hypothalamic dysfunction. Adipose tissue may provide signals to the central nervous system and gonadotropin regulatory areas either directly, by estrogen production, or indirectly, by the effects of relative fatness on temperature control and metabolic rate, or by both means. Women with hypothalamic dysfunction experience changes in the secretion of gonadotropins, luteinizing hormone, follicle-stimulating hormone, and estrogen. Weight gain restores postmenarcheal secretion patterns. This approach suggests that the secular trend toward earlier age at menarche reflects earlier attainment of critical weight as a result of improved nutrition and child care. In many societies, subnutrition may explain the observed submaximum fertility. This suggests a need to integrate family planning programs with nutrition programs in many developing countries. It is important to note that the prediction of the minimum weight for height for onset and maintenance of ovulatory cycles is from total water as percentage of body weight. Although the percentage of fat in the body is inversely related to the percent of body water, only the latter is predictive. Successful prediction of the minimum weights for height is related to a lean mass/fat ratio represented by about 17% fat of body weight at menarche and 22% of body weight at the completion of growth at age 18 years.     

What Is the Role of Cognitive-Behavior Therapy in Patient Management?

This review summarizes the role of cognitive-behavior therapy (CBT) in obesity treatment. Although not a specific intervention per se, CBT is the systematic application of principles of social cognitive theory to modify behaviors that are thought to contribute to or maintain obesity. Most forms of CBT include the use of five strategies: self-monitoring and goal setting; stimulus control for the modification of eating style, activity, and related habits; cognitive restructuring techniques that focus on challenging and modifying unrealistic or maladaptive thoughts or expectations; stress management; and social support. The use of these strategies in comprehensive obesity programs has been helpful in improving short-term weight losses, but long-term success remains elusive, even though these strategies are predictors of long-term weight loss maintenance. Given that obesity is a chronic condition, not unlike hypertension or diabetes, CBT interventions will need to focus on broader treatment outcomes, such as improved metabolic profiles, quality of life, psychological functioning, and physical fitness. In addition, new methods for delivering CBT interventions should be explored, including home-based programs and combination with adjunctive pharmacotherapy delivered in primary care centers.     

Small weight gain is not associated with development of insulin resistance in healthy, physically active individuals.

We investigated whether weight gain alters insulin sensitivity and leptin levels in physically active individuals. Six (5 males and 1 female; age 26.6+/-1.0 years; BMI 21.5+/-0.9, body fat 17.4+/-2.2%) healthy individuals were enrolled in an overfeeding study (caloric surplus 22.5-26.5 kcal/kg/day) to achieve up to 10% weight gain over 4-6 week period with subsequent weight maintenance over additional 2 weeks. The participants were requested to maintain their previous physical activity which in all of them included 45-60 min training sessions at the gym 2-3 times/week. RESULTS: BMI increased to 23.4+/-0.9 (4.4 kg weight gain; p<0.05) and body fat to 21.0+/-2.8% (p < 0.05) over the period of active weight gain and remained stable over the two week period of weight maintenance; fasting plasma glucose and serum insulin remained unchanged; serum leptin nearly doubled (3.8+/-1.0 vs 6.4+/-1.9 ng/ mL; p < 0.05); insulin sensitivity, when expressed per kg of the total body (11.1+/-1.6 vs 12.4+/-2.1 mg/kg/min; p = NS), and lean body mass (13.4+/-1.9 vs 15.7+/-2.6 mg/kgLBM/min; p = NS), did not decrease after weight gain. On the contrary, insulin action had improved in 5 out of 6 individuals. In conclusion, the data presented in this preliminary report indicate that a small weight gain due to overfeeding in lean, healthy, physically active individuals is associated with rise in circulating leptin levels but not with worsening of insulin action.     

Does Weight Loss Maintenance Become Easier Over Time?

Objective: Studies of health‐related behaviors, including weight loss, have shown that risk of relapse decreases over time, although reasons for this relationship are unclear. The purpose of this cross‐sectional study was to determine if subjects who have maintained weight losses for varying periods of time report different strategies for weight loss maintenance or differences in the effort and pleasure associated with weight maintenance behaviors. Research Methods and Procedures: Subjects were 758 women and 173 men who had maintained losses of at least 30 lb (mean = 60 lb) for 2 years or longer (mean = 6.8 ± 7.0 years). Self‐administered questionnaires assessed subjects’ use of weight maintenance strategies in the past year and their perceptions of the effort, attention, and pleasure associated with weight maintenance. Results: Subjects who had maintained weight losses longer used fewer weight maintenance strategies and reported that less effort was required to diet and maintain weight and that less attention was required to maintain weight. The pleasure derived from exercise, low‐fat eating, and maintaining weight was unrelated to duration of weight loss maintenance. Discussion: As duration increases, a shift in the balance between the effort and pleasure of weight maintenance may occur. This shift may increase the likelihood of continued maintenance.     

Individual differences in physical activity are closely associated with changes in body weight in adult female rhesus monkeys (Macaca mulatta)

The increased prevalence of overweight adults has serious health consequences. Epidemiological studies suggest an association between low activity and being overweight; however, few studies have objectively measured activity during a period of weight gain, so it is unknown whether low activity is a cause or consequence of being overweight. To determine whether individual differences in adult weight gain are linked to an individual's activity level, we measured activity, via accelerometry, over a prolonged period (9 mo) in 18 adult female rhesus monkeys. Weight, food intake, metabolic rate, and activity were first monitored over a 3-mo period. During this period, there was mild but significant weight gain (5.5 +/- 0.88%; t =-6.3, df = 17, P < 0.0001), whereas caloric intake and activity remained stable. Metabolic rate increased, as expected, with weight gain. Activity level correlated with weight gain (r = -0.52, P = 0.04), and the most active monkeys gained less weight than the least active monkeys (t = -2.74, df = 8, P = 0.03). Moreover, there was an eightfold difference in activity between the most and least active monkeys, and initial activity of each monkey was highly correlated with their activity after 9 mo (r = 0.85, P < 0.0001). In contrast, food intake did not correlate with weight gain, and there was no difference in weight gain between monkeys with the highest vs. lowest caloric intake, total metabolic rate, or basal metabolic rate. We conclude that physical activity is a particularly important factor contributing to weight change in adulthood and that there are large, but stable, differences in physical activity among individuals.     

Physical activity patterns using accelerometry in the National Weight Control Registry

The National Weight Control Registry (NWCR) was established in 1993 to examine characteristics of successful weight‐loss maintainers. This group consistently self‐reports high levels of physical activity. The aims of this study were to obtain objective assessments of physical activity in NWCR subjects and compare this to physical activity in both normal‐weight and overweight controls. Individuals from the NWCR (n = 26) were compared to a never obese normal‐weight control group matched to the NWCR group's current BMI (n = 30), and an overweight control group matched to the NWCR group's self‐reported pre‐weight‐loss BMI (n = 34). Objective assessment of physical activity was obtained for a 1‐week period using a triaxial accelerometer. Bouts of moderate‐to‐vigorous physical activity (MVPA) ≥10 min in duration, as well as nonbout MVPA (bouts of MVPA 1–9 min in duration) were summed and characterized. NWCR subjects spent significantly (P = 0.004) more time per day in sustained bouts of MVPA than overweight controls (41.5 ± 35.1 min/day vs. 19.2 ± 18.6 min/day) and marginally (P = 0.080) more than normal controls (25.8 ± 23.4). There were no significant differences between the three groups in the amount of nonbout MVPA. These results provide further evidence that physical activity is important for long‐term maintenance of weight loss and suggest that sustained volitional activity (i.e., ≥10 min in duration) may play an important role. Interventions targeting increases in structured exercise may be needed to improve long‐term weight‐loss maintenance.     

Effect of Postpartum Exercise on Mothers and their Offspring: A Review of the Literature

Epidemiological studies suggest that childbearing may contribute to the development of obesity. In the past 12 years, several cross‐sectional and randomized trials have addressed the effect of postpartum exercise on weight loss and/or energy balance in mostly lactating women. These studies suggest that moderate exercise without specific calorie restriction does not promote greater weight or fat loss. This may be because exercise may promote greater energy intake and/or reduced energy expenditure from nonexercise physical activity (thus preventing negative energy balance), but further research is needed. Regular exercise, however, is likely to have other important health benefits after childbirth. A few published studies suggest that postpartum exercise improves aerobic fitness, high‐density lipoprotein‐cholesterol levels, and insulin sensitivity. Exercise may also enhance psychological well‐being, but controlled clinical studies are needed. Although two published studies have addressed whether exercise training attenuates lactation‐induced bone loss, better controlled studies are needed to determine whether postpartum weight‐bearing exercise can improve bone mineral density in lactating and nonlactating women alike. In lactating women, several studies have collectively determined that neither acute nor regular exercise has adverse effects on a mother's ability to successfully breast‐feed. It needs to be determined whether a woman's participation in regular exercise after childbirth will improve her ability to mother or instill lifetime habits of regular physical activity in either herself or her offspring. Overall, published studies have established the importance of regular exercise during the postpartum period. More research, however, is needed in this important area.     

Effects of chronic weight perturbation on energy homeostasis and brain structure in mice

Maintenance of reduced body weight in lean and obese human subjects results in the persistent decrease in energy expenditure below what can be accounted for by changes in body mass and composition. Genetic and developmental factors may determine a central nervous system (CNS)-mediated minimum threshold of somatic energy stores below which behavioral and metabolic compensations for weight loss are invoked. A critical question is whether this threshold can be altered by environmental influences and by what mechanisms such alterations might be achieved. We examined the bioenergetic, behavioral, and CNS structural responses to weight reduction of diet-induced obese (DIO) and never-obese (CON) C57BL/6J male mice. We found that weight-reduced (WR) DIO-WR and CON-WR animals showed reductions in energy expenditure, adjusted for body mass and composition, comparable (-10-15%) to those seen in human subjects. The proportion of excitatory synapses on arcuate nucleus proopiomelanocortin neurons was decreased by ～50% in both DIO-WR and CON-WR mice. These data suggest that prolonged maintenance of an elevated body weight (fat) alters energy homeostatic systems to defend a higher level of body fat. The synaptic changes could provide a neural substrate for the disproportionate decline in energy expenditure in weight-reduced individuals. This response to chronic weight elevation may also occur in humans. The mouse model described here could help to identify the molecular/cellular mechanisms underlying both the defense mechanisms against sustained weight loss and the upward resetting of those mechanisms following sustained weight gain.     

A Statewide Intervention Reduces BMI in Adults: Shape Up Rhode Island Results

Given the epidemic of obesity, approaches to weight loss that can be applied on a community, state, or national level are needed. We report results from Shape Up Rhode Island 2007 (SURI), a statewide Internet‐based program involving team‐based competition to increase physical activity and achieve weight loss. A total of 4,717 adults (84% women; mean BMI = 29.6 kg/m²) enrolled in the 16‐week weight loss competition of SURI and 3,311 completed at least 12 weeks. Completers reported losing 3.2 ± 3.4 kg, and 30% achieved a clinically significant weight loss of ≥5%. Although modest, these weight losses shifted the BMI distribution from a mean BMI of 29.4 to a mean of 28.2 kg/m² and reduced the population that was obese from 39 to 31%. More conservative intent‐to‐treat analyses and analysis of 132 participants with objective weights still showed a significant reduction in BMI of ?0.8 units. These findings suggest that statewide weight loss campaigns can produce modest weight losses in large numbers of participants. These data provide a benchmark that can be used for comparisons with other statewide campaigns. Research on ways to improve such campaigns is needed.