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The thermogenic responses to overfeeding and cold are differentially regulated.
Peterson, CM, Lecoultre, V, Frost, EA, Simmons, J, Redman, LM, Ravussin, E
Obesity (Silver Spring, Md.). 2016;(1):96-101
Abstract
OBJECTIVE Brown adipose tissue (BAT) is a highly metabolic tissue that generates heat and is negatively associated with obesity. BAT has been proposed to mediate both cold-induced thermogenesis (CIT) and diet-induced thermogenesis (DIT). Therefore, it was investigated whether there is a relationship between CIT and DIT in humans. METHODS Nine healthy men (23 ± 3 years old, 23.0 ± 1.8 kg m(-2) ) completed 20 min of cold exposure (4°C) 5 days per week for 4 weeks. Before and after the intervention, CIT (the increase in resting metabolic rate at 16°C relative to 22°C) was measured by a ventilated hood indirect calorimeter, whereas DIT was measured as the 24-h thermic response to 1 day of 50% overfeeding (TEF150% ) in a respiratory chamber. RESULTS After the cold intervention, CIT more than doubled from 5.2% ± 14.2% at baseline to 12.0% ± 11.1% (P = 0.05), in parallel with increased sympathetic nervous system activity. However, 24-h energy expenditure (2,166 ± 206 vs. 2,118 ± 188 kcal day(-1) ; P = 0.15) and TEF150% (7.4% ± 2.7% vs. 7.7% ± 1.6%; P = 0.78) were unchanged. Moreover, there was no association between CIT and TEF150% at baseline or post-intervention, nor in their changes (P ≥ 0.47). CONCLUSIONS Cold acclimation resulted in increased CIT but not TEF150% . Therefore, it is likely that CIT and DIT are mediated by distinct regulatory mechanisms.
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No effect of caloric restriction on salivary cortisol levels in overweight men and women.
Tam, CS, Frost, EA, Xie, W, Rood, J, Ravussin, E, Redman, LM
Metabolism: clinical and experimental. 2014;63(2):194-8
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Plain language summary
Alterations in normal cortisol patterns have been observed in people who are obese. The effect of weight loss on cortisol levels, a measure of hypothalamic pituitary adrenal (HPA) activity, in overweight individuals is not known. The aim of this study was to test the hypothesis that 6 months of moderate caloric restriction would alter morning and diurnal salivary cortisol levels. Thirty-five overweight adults (average BMI 27.8 kg/m2) took part in this randomised control trial. Participants were assigned to either calorie restriction (CR: 25% reduction in energy intake), calorie restriction+exercise (CR+EX: 12.5% reduction in energy intake+12.5% increase in exercise energy expenditure) or control (healthy weight-maintenance diet) for 6 months. Salivary cortisol was measured at 8:00, 8:30, 11:00, 11:30, 12:30, 13:00, 16:00 and 16:30. Morning cortisol was defined as the mean cortisol concentration at 08:00 and 08:30. Diurnal cortisol was calculated as the mean of the 8 cortisol measures across the day. Across all groups, higher morning and diurnal cortisol levels were associated with impaired insulin sensitivity. There was no significant effect of group, time or sex on morning or diurnal cortisol levels. The authors concluded that a 10% weight loss with a 25% CR diet alone or with exercise did not impact morning or diurnal salivary cortisol levels in overweight individuals. Their findings suggest that prolonged restriction of energy intake is not perceived by the body as a stressor, and therefore CR may present a viable intervention.
Abstract
OBJECTIVE The effect of weight loss by diet or diet and exercise on salivary cortisol levels, a measure of hypothalamic pituitary adrenal activity, in overweight individuals is not known. The objective was to test the hypothesis that 24 weeks of moderate caloric restriction (CR) (25%) by diet or diet and aerobic exercise would alter morning and diurnal salivary cortisol levels. DESIGN AND SETTING Randomized control trial in an institutional research center. PARTICIPANTS Thirty-five overweight (BMI: 27.8±0.7 kg/m(2)) but otherwise healthy participants (16 M/19 F). INTERVENTION Participants were randomized to either calorie restriction (CR: 25% reduction in energy intake, n=12), calorie restriction+exercise (CR+EX: 12.5% reduction in energy intake+12.5% increase in exercise energy expenditure, n=12) or control (healthy weight-maintenance diet, n=11) for 6 months. MAIN OUTCOME MEASURE Salivary cortisol measured at 8:00, 8:30, 11:00, 11:30, 12:30, 13:00, 16:00 and 16:30. Morning cortisol was defined as the mean cortisol concentration at 08:00 and 08:30. Diurnal cortisol was calculated as the mean of the 8 cortisol measures across the day. RESULTS In the whole cohort, higher morning and diurnal cortisol levels were associated with impaired insulin sensitivity (morning: P=0.004, r(2)=0.24; diurnal: P=0.02, r(2)=0.15). Using mixed model analysis, there was no significant effect of group, time or sex on morning or diurnal cortisol levels. CONCLUSION A 10% weight loss with a 25% CR diet alone or with exercise did not impact morning or diurnal salivary cortisol levels.
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Interaction between dietary fat and exercise on excess postexercise oxygen consumption.
Frost, EA, Redman, LM, de Jonge, L, Rood, J, Zachwieja, JJ, Volaufova, J, Bray, GA, Smith, SR
American journal of physiology. Endocrinology and metabolism. 2014;(9):E1093-8
Abstract
The objective of this study was to determine the effect of increased physical activity on subsequent sleeping energy expenditure (SEE) measured in a whole room calorimeter under differing levels of dietary fat. We hypothesized that increased physical activity would increase SEE. Six healthy young men participated in a randomized, single-blind, crossover study. Subjects repeated an 8-day protocol under four conditions separated by at least 7 days. During each condition, subjects consumed an isoenergetic diet consisting of 37% fat, 15% protein, and 48% carbohydrate for the first 4 days, and for the following 4 days SEE and energy balance were measured in a respiration chamber. The first chamber day served as a baseline measurement, and for the remaining 3 days diet and activity were randomly assigned as high-fat/exercise, high-fat/sedentary, low-fat/exercise, or low-fat/sedentary. Energy balance was not different between conditions. When the dietary fat was increased to 50%, SEE increased by 7.4% during exercise (P < 0.05) relative to being sedentary (baseline day), but SEE did not increase with exercise when fat was lowered to 20%. SEE did not change when dietary fat was manipulated under sedentary conditions. Physical activity causes an increase in SEE when dietary fat is high (50%) but not when dietary fat is low (20%). Dietary fat content influences the impact of postexercise-induced increases in SEE. This finding may help explain the conflicting data regarding the effect of exercise on energy expenditure.
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The technology boom: a new era in obesity management.
Gilmore, LA, Duhé, AF, Frost, EA, Redman, LM
Journal of diabetes science and technology. 2014;(3):596-608
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Abstract
As technology continues to develop rapidly, the incidence of obesity also continues to climb at an alarming rate. The increase in available technology is thought to be a contributor in the obesogenic environment, yet at the same time technology can also be used to intervene and improve health and health behaviors. This article reviews the components of effective weight management programs and the novel role that technology, such as SMS, websites, and smartphone apps, is playing to improve the success of such programs. Use of these modern technologies can now allow for individualized treatment recommendations to be delivered to individuals remotely, increased self-monitoring/tracking of health-related data, broader and more rapid dissemination of health information/recommendations, and increased patient-dietician/physician contact. The use of technology in weight management programs results in improved long-term weight management, and in most cases improved cost-effectiveness. Rather than blaming increased food intake and sedentary lifestyle on technology, rapidly developing and innovative technologies should be used to our advantage and deployed to combat the obesity epidemic.
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Perioperative considerations for the patient on herbal medicines.
Sabar, R, Kaye, AD, Frost, EA
Middle East journal of anaesthesiology. 2001;(3):287-314
Abstract
Herbal medicines have enormous presence in the United States health care system. There is an increasing trend towards reimbursement of herbal medicines by insurance companies, which further encourage their utilization. Herbs are listed under the "supplement" category by the Food and Drug Administration. The Dietary Supplement and Health Education Act signed into law in October 1994, requires no proof of efficacy, no demonstration of safety, and sets no standards for quality control for the products labeled as "supplements" thereby increasing the risk of adverse effects of these herbs. The United States has experienced an epidemic of over-the-counter "natural" products over the last two decades; but there is little motivation for the manufactures to conduct randomized, placebo-controlled, double-blinded clinical trials to unequivocally prove the safety and efficacy of these drugs. Physicians, irrespective of their specialty, should not underestimate the potential risks associated with the use of herbs as reports indicate that within the last two decades, more than 100 herbogenic deaths have occurred, many serious complications have been reported, patients have required renal dialysis, renal transplantation and hepatic transplantation after taking botanicals. Internists must inquire about the patient's use of herbal products. In addition, the education of each patient regarding the serious, potential drug-herb interactions should be a routine component of preoperative assessment. The American Society of Anesthesiologists (ASA) recommends that all herbal medications should be discontinued 2-3 weeks prior to an elective surgical procedure. If the patient is not sure of the content of the herbal medicine, he/she should be urged to bring the container so that an attempt can be made to review the contents of the preparation. While such an action holds some promise in the elective setting, emergency care should be based on a thorough drug-intake history from the patient or a relative, if possible. Medical research and medical literature in general has not addressed this new group of health supplements, despite the fact that many of these herbs have the potential to cause serious health problems and drug interations. There is a need to conduct scientific clinical trials to study the anesthetic drug responses to commonly used neutraceutical agents.