Thermogenesis and weight loss in obese individuals: a primary association with organochlorine pollution

Abstract

The main objective of this study was to investigate the potential impact of body organochlorine (OC) pollution on the adaptive change in thermogenesis induced by body weight loss. Fat mass (FM), fat-free mass (FFM), and sleeping metabolic rate (SMR) were measured in obese individuals before and after a weight-reducing program. The measured values of SMR were then compared to those predicted from a reference equation established from FM and FFM in control subjects. Plasma OC, leptin, total tri-iodothyronine, and free thyroxine concentrations were also measured in obese subjects before and after weight loss. After weight loss, the measured decrease in SMR was greater than that predicted by changes in FM and FFM. Increased plasma OC concentration was the factor explaining the greatest proportion of the difference between predicted and measured SMR changes induced by body weight loss. OC pollution seems to be a new factor affecting the control of thermogenesis in some obese individuals experiencing body weight loss. IntroductionThe total body burden of organochlorines (OCs) is greater in obese than in lean individuals because of their increased body fat stores and plasma and adipose tissue OC concentration. 1 In response to body weight loss, OC concentration increases in plasma 2,3 and they are more susceptible to exert their adverse effects on metabolism. In this regard, the increase in OC concentration induced by weight loss has been shown to be an independent predictor of the decrease in plasma tri-iodothyronine (T 3 ), 4 resting metabolic rate, 4 and skeletal muscle oxidative enzyme activity 5 resulting from weight loss. Considering that OCs are also known to alter the functionality of mitochondria, 6 it is realistic to hypothesize that the increase in plasma OCs is a factor implicated in the adaptive decrease in thermogenesis occurring with weight loss. 7,8 To investigate this issue, we measured the sleeping metabolic rate (SMR) and its deviations from predicted values before and after weight loss in obese individuals. This allowed an estimation of adaptive thermogenesis, defined as the difference between the expected decrease in SMR due to the decreases of fat mass (FM) and fat-free mass (FFM) and the decrease in SMR really measured. This difference was then used as the dependent variable in a stepwise multiple regression analysis to compare the contribution of OCs to variations in thermogenesis to that of other factors known to affect thermogenesis in the context of a weight-reducing program. MethodsIn all, 58 men and 28 women with a wide range of body weight (47.5-146.1 kg) were used as control subjects to establish a reference equation predicting the SMR from gender, age, FM, and FFM. Eight men and seven women who gave their written consent to participate in a weight-loss program approved by the Laval University Ethics Committee and for whom all the variables of interest were available before and after weight loss were analyzed in the present study. The weight-loss program, which was conducted between 1995...

Clinical significance of adaptive thermogenesis

“…Indeed, in the context of a 15-week weight reduction program, an increase in plasma organochlorine concentration has successively been shown to be the best predictor of the significant decrease in resting metabolic rate 61 and of the significant greater than predicted decrease in sleeping EE, 12 explaining 32 and 47% of these variables, respectively (see Table 3). Interestingly, in this last study, 12 this corresponded to a greater percentage than what change in plasma leptin concentration (20%) and plasma leptin concentration after weight loss (13%) did explain. These relationships are surprising but could nevertheless be explained, at least partly, through the relation between plasma organochlorine concentration and lowered plasmafree thyroxine and total thyroxine levels that have been reported in several human studies.…”

“…Indeed, it has been well demonstrated that the decrease in EE during energy restriction and weight loss programs can be greater than expected from the decrease in fat mass and fat-free mass, [3][4][5] despite these two variables accounting for over 82% of the variance in EE. [6][7][8][9][10] This paper thus specifically focuses on an adaptive reduction in EE in response to energy restriction that can be observed in any component of total EE, 3,4,11,12 traditionally divided into resting and non-resting EEs (including physical activity and non-exercise activity EEs), and thermic effect of food.…”

Airborne occupational exposure, ABO phenotype, and risk of obesity

“…In a recent paper, Yudkin et al 6 suggested that similar inflammatory mediators may be a link connecting obesity and coronary heart disease. The suggestion that environmental pollutants may be a risk factor for obesity has gained support from the results of another recent study by Tremblay et al 7 In a 15-week weightloss program of 15 obese subjects and 86 nonobese controls, they showed that the obese group had lost on average a little more than 10 kg, and that, as a group, their metabolic rate had decreased by approximately 12%. In a multiple regression analysis, total plasma organochlorine (OC) concentration was the factor explaining the greatest proportion of the difference between predicted and measured metabolic rate changes during sleep induced by body weight loss.…”

Relationship between severity of nocturnal desaturation and adaptive thermogenesis: preliminary data of apneic patients tested in a whole-body indirect calorimetry chamber

“…It could also be defined as a non-obligatory thermogenesis which is affected by some hormones and neurosystems as well as by some environmental factors such as pollution. 17 In this regard, the main factor of this study is OSAS which is also susceptible to influence this adaptive component of energy expenditure. We hypothesized that an hypoxic stress that is sufficiently severe may promote a decreased adaptive thermogenesis in apneic patients.…”