Energy utilization in human obesity

From the past to future: from energy expenditure to energy intake to energy expenditure

Although most recent research on energy balance focusses on energy intake (EI) there is still need to think about both sides of the energy balance. Current research on energy expenditure (EE) relates to metabolic adaptation to negative energy balance, mitochondrial metabolism associated with aging, obesity and type 2 diabetes mellitus, the role of EE in hunger and appetite control, non-shivering thermogenesis and brown adipose tissue activity, cellular bioenergetics as a target of obesity treatment and the evolutionary and ecological determinants of EE in humans and other primates. As far as regulation of energy balance is concerned there is recent evidence that EE rather than body weight is under tight control. Biologically, EE is maintained within a narrow physiological range. An EE-set point has been proposed as the width between the upper and lower boundaries of the individual EE range. Regulation of EE may fail in very obese patients with an EI above their upper boundary and after drastic weight loss when patients may go far below their lower EE boundary and thus are loosing control. In population studies, fat-free mass (FFM) and its composition (that is, the proportion of high to low metabolic rate organs) are major determinants of EE. It is tempting to speculate that tight biologic control of EE is related to brain energy need, which is preserved at the cost of peripheral metabolism. There is a moderate heritability of EE, which is independent of the heritability of FFM. In future, metabolic phenotyping should focus on the EE-FFM relationship rather than on EE-values alone.

Patterns of physical activity in free-living adults in the Southern United States

OBJECTIVE

To examine the relationship between the amount and patterns of physical activity (PA), body fatness, and age in a heterogeneous adult population in the free living.

DESIGN

Cross-sectional study of the amount of PA over a 1-week period. The amount of body movements during PA (PA counts*10(3)) and time spent on various PA intensity categories were calculated from a triaxial accelerometer and compared with subject characteristics, including body fat from hydrodensitometry.

PARTICIPANTS

Adult healthy men (n=48) and women (n=72) were recruited from the Nashville, Tennessee area and their PA was monitored in their free-living environment.

RESULTS

The average weekday PA counts (176.5+/-60.3, P=0.002, r(2)=0.294), PA counts day-to-day variability (47.3+/-32.7, P=0.002, r(2)=0.286), daily maximum PA counts (241.9+/-89.2, P=0.001, r(2)=0.327), minute-to-minute variability on weekdays (0.281+/-0.091, P=0.001, r(2)=0.362), and the difference between maximum and minimum daily PA counts (130.6+/-78.3, P=0.008, r(2)=0.243) were significantly and negatively correlated with body fatness. During awake time, both men and women spent 10-12 h on low intensity (1.0-2.9 metabolic equivalents (METs)) PA, approximately 1 h on moderate (3.0-5.9 MET), and less than 10 min on vigorous (>6.0 MET) PA each day. On weekends, men and women spent more time at rest (1 MET), less time on low-intensity PA, and men spent more time on moderate PA than on weekdays.

CONCLUSIONS

In adults living in the Southern US the amount of free-living PA was negatively correlated with body fatness. Both men and women spent the majority of active time on low and moderate PA. PA patterns on weekends were different than on weekdays and were related to sex and age, but not to body fatness.

SPONSORSHIP

National Institutes of Health, US.

The safety and efficacy of pharmaceutical and herbal caffeine and ephedrine use as a weight loss agent

Since passage of the Dietary Supplement Health and Education Act of 1994, the sale of herbal dietary supplements containing caffeine and ephedrine for weight loss has become widespread in the United States. Reports of adverse events associated with the use of these non-prescription supplements have raised concerns in the United States regulatory community. Restricting the use of these products is now being considered. Such restriction should be based upon controlled clinical trials. This review of the literature in Medline relative to the use of caffeine and ephedrine in the treatment of obesity concludes that caffeine and ephedrine are effective in causing weight loss. Caffeine and ephedrine give equivalent weight loss to Diethylpropion and superior weight loss compared to dexfenfluramine. Caffeine and ephedrine have a long history of safe, non-prescription use. The adverse events accompanying acute dosing are mild and transient. Adverse events with caffeine and ephedrine reach and remain at placebo levels after 4-12 weeks of continuous treatment, but data from randomized trials up to 6 months only are available. Obesity is chronic, requires chronic treatment, its incidence is increasing and it has few effective treatments. The benefits of caffeine and ephedrine in treating obesity appear to outweigh the small associated risks. Restriction of dietary herbal supplements containing caffeine and ephedrine, often with other ingredients, should be based on controlled clinical trials of these products.

Basal metabolic adaptation of the Evenki reindeer herders of Central Siberia

Previous research has suggested that basal metabolic rates (BMRs of indigenous circumpolar populations are elevated, perhaps as an adaptation to chronic, severe cold stress. This study examines variation in BMR among indigenous (Evenki) and nonindigenous (Russian immigrant) populations living in Central Siberia to determine: 1) whether the Evenki show evidence of increased metabolic rates, and 2) whether the metabolic responses of the Evenki are different from those of the recent Russian migrants ("controls"). BMRs were measured among 58 Evenki (19 men, 39 women) and 24 Russian (8 men, 16 women) adults (18-56 years of age) from three Siberian villages. Measured BMRs were compared to those predicted based on body weight and body SA (Consolazio et al., 1963; Schofield, 1985a,b). BMRs per unit weight and FFM were similar in Evenki and Russian men, whereas Evenki women had higher BMRs than their Russian peers. Relative to the Schofield (body weight) norms, Evenki men and women and Russian men all showed modest elevations in BMR, whereas Russian women had lower than expected BMRs. Compared to the Consolazio (surface area) estimates, both Evenki men and women showed significant elevations in BMR. Russian men also showed higher than expected BMRs, while those of Russian women were slightly below predicted levels. Age-related declines in BMR were evident among the women of both ethnic groups, but not among the men. Additionally, residence location was an important predictor of metabolic variation in the Evenki, with those of the more traditional village showing greater elevations in BMR. These results suggest that the Evenki display elevated metabolic needs, and this long-term adaptation reflects the interaction of genetics and level of acculturation. Am. J. Hum. Biol. 12:75-87, 2000. Copyright 2000 Wiley-Liss, Inc.

Determinants of obesity in relation to socioeconomic status among middle-aged Swedish women

BACKGROUND

It has been previously demonstrated that obesity is common among women with low socioeconomic status (SES), but the factors accounting for this association are not well known. According to our hypothesis, low SES is associated with psychosocial stress, an unhealthy lifestyle, and reproductive history, which may increase the likelihood of women with low SES to be overweight or obese.

METHODS

We examined overweight and obesity in relation to SES among 300 healthy women ages 30-65 years, who constitute the control group of the Stockholm Female Coronary Risk Study, a population-based case-control study of women with coronary heart disease. This control group was compared with a large population-based sample and found to be representative of healthy Swedish women ages 30-65 years. We used an aggregate of education and occupation as a measure of SES and defined overweight as body mass index (BMI) between 23.8 and 28.6 kg/m2 and obesity as BMI > 28.6 kg/m2.

RESULTS

Low SES was a strong determinant of overweight and obesity among middle-aged healthy Swedish women. The odds of being overweight or obese increased with lower social position. After adjustment for age, the odds ratios for overweight and obesity among women in a low vs high position were 2.2 [95% confidence interval (CI) 1.1 to 4.4) and 2.7 (95% CI 1.1 to 6.7), respectively. Both low social position and obesity were related to reproductive history (higher parity and earlier age at menarche), unhealthy dietary habits, and unfavorable psychosocial factors (poor quality of life, low self-esteem, and job strain). These factors together explained 53% of the low-SES-obesity association.

CONCLUSIONS

Reproductive history, unhealthy dietary habits, and psychosocial stress accounted for a large part of the association between low SES and obesity. Dietary habits and psychosocial stress are potentially modifiable factors, which should be taken into account in intervention programs among women with low SES.

Hormonal control of thermogenesis and energy dissipation

Facultative (adaptive) thermogenesis is primarily controlled by the sympathetic nervous system (SNS). The participation of thyroid hormones in adaptive thermogenesis has been considered minor or, at most, permissive. The finding of type II-thyroxine (T(4)) 5'-deiodinase in brown adipose tissue (BAT) has opened a way to uncover a more important role for thyroid hormone in adaptive thermogenesis. This enzyme is activated by the. SNS and insulin. When activated, it generates high BAT concentrations of triiodothyronine (T(3)) from plasma T(4). T(3), intrinsically 10 times more active than T(4), has been shown essential for the expression of the key protein in BAT thermogenesis, uncoupling protein (UCP). The multihormonal control of BAT type-II 5'-deiodinase and the marked influence of T(3) on UCP and BAT thermogenesis suggest that the local control of T(3) generation may be an important source of variability in the potential of mammals to maintain temperature and dissipate energy.

Socioeconomic and behavioral correlates of body mass index in black adults: the Pitt County Study

BACKGROUND

Obesity is more prevalent among Black women than Black men, but there is little information on the correlates of obesity in Blacks. This study describes the relations of sociodemographic factors and health behaviors to body mass index in a southern, Black population.

METHODS

In 1988, a community probability sample of 1784 Black adults, aged 25 to 50, was examined in Pitt County, NC.

RESULTS

More women than men were at least 20% overweight (57% vs 36%). The relation of socioeconomic status (a composite of education and occupation) to age-adjusted body mass index level was inverse in women but not in men. Body mass index did not differ with either current energy intake or energy expenditure. Smokers and drinkers had lower age-adjusted levels than non-smokers and abstainers.

CONCLUSIONS

Since the excess body mass index levels associated with low socioeconomic status in women could not be explained after controlling for adverse health behaviors, further epidemiologic study of risk factors for obesity in Black women is recommended.

Measurement reliability and reactivity using repeated measurements of resting energy expenditure with a face mask, mouthpiece, and ventilated canopy

This investigation evaluated the measurement reliability and reactivity of repeated measurements of resting energy expenditure using different methods of data collection. Thirty subjects were randomly assigned to either face mask, mouthpiece/nose clip, or ventilated canopy collection systems for 45 min a day over 3 days. Results indicated that there were no significant differences among data collection systems nor were there any differences either within or between systems over time. Across all three days of measurement, the first 5 min of data collection on all systems were reactive compared to the subsequent 40 min of assessment. Analyses indicated that acceptable reliability coefficients were obtained after 20 min of continuous data collection in the ventilated canopy and after 40 min with the face mask after a 5-min acclimation period. The results suggest that, following an acclimation period, a single 20-min assessment of resting energy expenditure in both a face mask and ventilated canopy are stable and reliable.

Management of obesity in adolescence

A great deal of the discouragement about treating adolescents who are obese is related to the traditional treatment approaches. Obesity is a complex problem needing comprehensive treatment. Focusing on weight loss as a short-term goal is unreasonable because of individual variation in the physiologic potential to lose weight. Short-term goals and rewards are related to adopting daily habits that will lead to a decrease in energy storage in the long term. Support for changing habits and improving psychosocial adjustment is a necessary component of effective treatment, enabling patients and their families to make changes.