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Article Archive: Energy Metabolism

Developmental changes in the relationship between leptin and adiposity among Tsimané children and adolescents
Huanca T, Kuzawa CW, Leonard WR, McDade TW, Reyes-García VE, Sharrock KC, Tanner S, Vadez V
Am J Hum Biol 20(4):392-8
1 July 2008
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Leptin is thought to signal energy stores, thus helping the body balance energy intake and expenditure. However, the strong relationship between leptin and adiposity in populations with adequate nutrition or common obesity is not universal across ecologic contexts, and leptin often correlates only weakly, or not at all, with adiposity in populations of lean or marginally-nourished males. To clarify whether the relationship between adiposity and leptin changes during development, this study examines leptin and body fat among children and adolescents of lowland Bolivia. Anthropometric measures of body composition and dried blood spot samples were collected from 487 Tsimane' ranging from 2 to 15 years of age. Leptin was assayed using an enzyme immunoassay protocol validated for use with blood spot samples. In this population, leptin concentrations were among the lowest reported in a human population (mean +/- SD: 1.26 +/- 0.5 and 0.57 +/- 0.3 in females and males). In addition, the relationship between leptin and adiposity follows distinct developmental trajectories in males and females. In males, leptin is weakly correlated with most measures of body composition at all ages investigated. However, in females, the level of body fat and the strength of the correlation between body fat and leptin (a measure of its strength as a signal of energy stores) both increase markedly with age. These findings suggest a more important role of leptin as a signal of energy stores among females as they approach reproductive maturity, while raising questions about the function of this hormone in lean males.

Academic Articles by NU Faculty
Adiposity, Adolescent, Age Factors, Anthropometry, Body Mass Index, Bolivia/epidemiology, Child, Child, Energy Metabolism, Female, Humans, Leptin/metabolism, Male, Nutritional Status, Obesity/epidemiology, Obesity/metabolism, Obesity/physiopathology, Pilot Projects, Preschool
Do the obese have lower body temperatures? A new look at a forgotten variable in energy balance
Landsberg L, Leonard WR, Linsenmeier RA, Turek FW, Young JB
Trans Am Clin Climatol Assoc 120:287-95
1 January 2009
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Understanding the pathogenesis of obesity is now more important than ever, given the remarkable world-wide epidemic. This paper explores the potential role of core temperature in energy balance, and develops the hypothesis that basal temperature and changes in the temperature response in various situations contribute to the enhanced metabolic efficiency of the obese state. The argument is based on the important contribution that heat production makes in establishing the basal or resting metabolic rate, as well as on an analysis of the adaptive role played by changes in temperature in response to environmental challenge. If this hypothesis is validated, new therapeutic approaches may ensue.

Academic Articles by NU Faculty
Adaptation, Animals, Basal Metabolism, Biological, Body Temperature/physiology, Brown/physiology, Energy Metabolism, Humans, Models, Motor Activity, Obesity/etiology, Obesity/physiopathology, Physiological Adipose Tissue, Thermogenesis
Is obesity associated with lower body temperatures? Core temperature: a forgotten variable in energy balance
Landsberg L, Leonard WR, Linsenmeier RA, Turek FW, Young JB
Metabolism 58(6):871-6
1 June 2009
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The global increase in obesity, along with the associated adverse health consequences, has heightened interest in the fundamental causes of excessive weight gain. Attributing obesity to "gluttony and sloth", blaming the obese for overeating and limiting physical activity, oversimplifies a complex problem, since substantial differences in metabolic efficiency between lean and obese have been decisively demonstrated. The underlying physiological basis for these differences have remained poorly understood. The energetic requirements of homeothermy, the maintenance of a constant core temperature in the face of widely divergent external temperatures, accounts for a major portion of daily energy expenditure. Changes in body temperature are associated with significant changes in metabolic rate. These facts raise the interesting possibility that differences in core temperature may play a role in the pathophysiology of obesity. This review explores the hypothesis that lower body temperatures contribute to the enhanced metabolic efficiency of the obese state.

Academic Articles by NU Faculty
Basal Metabolism, Body Temperature Regulation, Energy Metabolism, Humans, Obesity/etiology, Obesity/physiopathology
Nutritional status and spousal empowerment among native Amazonians
Godoy RA, Leonard WR, McDade T, Patel A, Reyes-García V, Seyfried CF Jr, Tanner S, Vadez V
Soc Sci Med 63(6):1517-30
1 September 2006
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Researchers and development organizations have shown interest in individual empowerment because it presumably improves well-being. Estimates of empowerment's effects on well-being contain biases from the potential endogeneity of empowerment. Using data from a sexually egalitarian and highly autarkic society of foragers and horticulturalists in the Bolivian Amazon, the Tsimane', we overcome the problems that this poses by: (1) matching spouses' responses to the same questions about who makes decisions or who breaks ties in 10 domains to improve accuracy in measures of empowerment; and (2) using parental attributes of spouses as instrumental variables for spousal empowerment. Outcomes include two anthropometric indices of short-run nutritional status: body-mass index and age and sex-standardized z scores of mid-arm muscle area. The amount of empowerment of household heads did not affect their nutritional status or other indicators of their well-being, such as income, wealth, expenditures, happiness, social capital, or self-perceived health. It also did not affect the nutritional status of their offspring. Nor did it affect the difference in income, wealth, or monetary expenditures between spouses. The insubstantial effects persisted with other definitions of empowerment or types of regressions. We end with a discussion of why empowerment, despite its popularity in development discourse, has such tenuous links with objective indicators of well-being, and the implication of this finding for future studies of empowerment's effects.

Academic Articles by NU Faculty
Adult, Asian Continental Ancestry Group/statistics & numerical data, Basal Metabolism, Body Composition, Body Size, Calorimetry, Deuterium Oxide/diagnostic use, Energy Metabolism, Female, Humans, Indirect, Life Style, Male, Middle Aged, Motor Activity, Physical Exertion, Sex Factors, Siberia
Total energy expenditure in the Yakut (Sakha) of Siberia as measured by the doubly labeled water method
Leonard WR, Schoeller DA, Snodgrass JJ, Tarskaia LA
Am J Clin Nutr 84(4):798-806
1 October 2006
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BACKGROUND: Populations in transition to a Western lifestyle display increased incidences of obesity, type 2 diabetes, and other chronic diseases; the mechanisms responsible for these changes, however, remain incompletely understood. Although reduced physical activity has been implicated, few studies have accurately quantified energy expenditure in subsistence populations.

OBJECTIVE: The aim of the study was to examine the relation of total energy expenditure (TEE) and activity [physical activity level (PAL), activity energy expenditure (AEE), and weight-adjusted AEE (AEE/kg)] with body composition and lifestyle in the Yakut (Sakha), an indigenous high-latitude Siberian group.

DESIGN: We measured TEE using doubly labeled water and resting metabolic rate using indirect calorimetry in 28 young adults (14 women and 14 men) from Berdygestiakh, Russia.

RESULTS: The men had higher TEE (12,983 compared with 9620 kJ/d; P < 0.01), AEE (5248 compared with 3203 kJ/d; P < 0.05), AEE/kg (72.7 compared with 48.8 kJ . kg(-1) . d(-1); P < 0.05), and PAL (1.7 compared with 1.5; P = 0.09) than did the women, although this may reflect, in part, body size and composition differences. Overweight men and women had modestly higher TEEs than did lean participants; when adjusted for body size, activity levels were not significantly different between the groups. Persons with more traditional lifestyles had higher TEEs and PALs than did persons with more modernized lifestyles; this difference correlated with differences in participation in subsistence activities.

CONCLUSIONS: Activity levels in the Yakut were lower than those in other subsistence groups, especially the women, and were not significantly different from those in persons in industrialized nations. Persons who participated in more subsistence activities and consumed fewer market foods had significantly higher activity levels.

Academic Articles by NU Faculty
Adult, Asian Continental Ancestry Group/statistics & numerical data, Basal Metabolism, Body Composition, Body Size, Calorimetry, Deuterium Oxide/diagnostic use, Energy Metabolism, Female, <