Background— Obesity is a risk factor for impaired cardiac performance, particularly in women. Animal studies suggest that alterations in myocardial fatty acid metabolism and efficiency in obesity can cause decreased cardiac performance. In the present study, we tested the hypothesis that myocardial fatty acid metabolism and efficiency are abnormal in obese women. Methods and Results— We studied 31 young women (body mass index [BMI] 19 to 52 kg/m ² ); 19 were obese (BMI >30 kg/m ² ). Myocardial oxygen consumption (MV̇ o ₂ ) and fatty acid uptake (MFAUp), utilization (MFAU), and oxidation (MFAO) were quantified by positron emission tomography. Cardiac work was measured by echocardiography, and efficiency was calculated as work/MV̇ o ₂ . BMI correlated with MV̇ o ₂ ( r =0.58, P =0.0006), MFAUp ( r =0.42, P <0.05), and efficiency ( r =−0.40, P <0.05). Insulin resistance, quantified by the glucose area under the curve (AUC) during an oral glucose tolerance test, correlated with MFAUp ( r =0.55, P <0.005), MFAU ( r =0.62, P <0.001), and MFAO ( r =0.58, P <0.005). A multivariate, stepwise regression analysis showed that BMI was the only independent predictor of MV̇ o ₂ and efficiency ( P =0.0005 and P <0.05, respectively). Glucose AUC was the only independent predictor of MFAUp, MFAU, and MFAO ( P <0.05, <0.005, and <0.005, respectively). Conclusions— In young women, obesity is a significant predictor of increased MV̇ o ₂ and decreased efficiency, and insulin resistance is a robust predictor of MFAUp, MFAU, and MFAO. This increase in fatty acid metabolism and decrease in efficiency is concordant with observations made in experimental models of obesity. These metabolic changes may play a role in the pathogenesis of decreased cardiac performance in obese women.

Body composition is a key component for maintaining good general health and longevity. It can be influenced by a variety of factors, including genetics, environment, and lifestyle choices. The assessment of body composition is an essential tool for nutrition specialists to effectively evaluate nutritional status and monitor progression during dietary interventions. As humans age, there is a natural increase in fat mass coupled with a gradual decline in lean mass, specifically in bone and muscle mass. Individuals with a high body fat percentage are at a greater risk of cardiovascular diseases, type 2 diabetes, several types of cancer, and early mortality. Significant decreases in bone mineral density signify osteopenia and osteoporosis, while reductions in skeletal muscle mass increase the risk of developing sarcopenia. Moreover, undernutrition exacerbates the effects of many medical conditions and is important to address. Though weight tracking and calculation of BMI are used commonly by clinicians and dietitians, these measures do not provide insight on the relative contributions of fat mass and fat-free mass or the changes in these compartments that may reflect disease risk. Therefore, it is important that healthcare professionals have a critical understanding of body composition assessment and the strengths and limitations of the methods available.

Weight gain and behavioral patterns during college may contribute to overweight and obesity in adulthood. The aims of this study were to assess weight, exercise, and dietary patterns of 764 college students (53% women, 47% men) during freshman and sophomore years. Students had their weight and height measured and completed questionnaires about their recent exercise and dietary patterns. At the beginning of freshman year, 29% of students reported not exercising, 70% ate fewer than 5 fruits and vegetables daily, and more than 50% ate fried or high-fat fast foods at least 3 times during the previous week. By the end of their sophomore year, 70% of the 290 students who were reassessed had gained weight (4.1 ± 3.6 kg, p> .001), but there was no apparent association with exercise or dietary patterns. Future research is needed to assess the contributions of fat, muscle, and bone mass to observed weight gain and to determine the health implications of these findings.

Western lifestyles differ markedly from those of our hunter-gatherer ancestors, and these differences in diet and activity level are often implicated in the global obesity pandemic. However, few physiological data for hunter-gatherer populations are available to test these models of obesity. In this study, we used the doubly-labeled water method to measure total daily energy expenditure (kCal/day) in Hadza hunter-gatherers to test whether foragers expend more energy each day than their Western counterparts. As expected, physical activity level, PAL, was greater among Hadza foragers than among Westerners. Nonetheless, average daily energy expenditure of traditional Hadza foragers was no different than that of Westerners after controlling for body size. The metabolic cost of walking (kcal kg⁻¹ m⁻¹) and resting (kcal kg⁻¹ s⁻¹) were also similar among Hadza and Western groups. The similarity in metabolic rates across a broad range of cultures challenges current models of obesity suggesting that Western lifestyles lead to decreased energy expenditure. We hypothesize that human daily energy expenditure may be an evolved physiological trait largely independent of cultural differences.

Background: Weight loss, through calorie restriction or increases in energy expenditure via exercise, improves glucose tolerance and insulin action. However, exercise-induced energy expenditure may further improve glucoregulation through mechanisms independent of weight loss. Objective: The objective was to assess the hypothesis that weight loss through exercise-induced energy expenditure improves glucoregulation and circulating factors involved in insulin action to a greater extent than does similar weight loss through calorie restriction. Design: Sedentary men and women aged 50–60 y with a body mass index (kg/m²) of 23.5–29.9 were randomly assigned to 1 of 2 weight-loss interventions [12 mo of exercise training (EX group; n = 18) or calorie restriction (CR group; n = 18)] or to a healthy lifestyle (HL) control group (n = 10). The insulin sensitivity index and areas under the curve for glucose and insulin were assessed with an oral-glucose-tolerance test. Adiponectin and tumor necrosis factor α concentrations were measured in fasting serum. Fat mass was measured by dual-energy X-ray absorptiometry. Results: Yearlong energy deficits were not significantly different between the EX and CR groups, as evidenced by body weight and fat mass changes. The insulin sensitivity index increased and the glucose and insulin areas under the curve decreased in the EX and CR groups, remained unchanged in the HL group, and did not differ significantly between the EX and CR groups. Marginally significant increases in adiponectin and decreases in the ratio of tumor necrosis factor α to adiponectin occurred in the EX and CR groups but not in the HL group. Conclusions: Weight loss induced by exercise training or calorie restriction improves glucose tolerance and insulin action in nonobese, healthy, middle-aged men and women. However, it does not appear that exercise training–induced weight loss results in greater improvements than those that result from calorie restriction alone.

Research from JAMA Internal Medicine — Bone Mineral Density Response to Caloric Restriction–Induced Weight Loss or Exercise-Induced Weight Loss — A Randomized Controlled Trial