How does weight affect rmr

At visit C-3 after Finally, at visit C-4 the patients were out of ketosis 0. Table 1 , Fig. The measured RMR was not significantly different from the baseline at any time during the study, although a downward trend in these values was observed Fig.

Resting metabolic rate RMR changes during the study. RMR-expected refers to the change in energy expenditure explained by changes in free fat mass FFM or muscle mass.

The difference between the measured and expected RMR defined the degree of metabolic adaptation. At visit C-2 maximum ketosis , the measured RMR was At visit C-3, the measured RMR was Finally, at visit C-4, the measured RMR was None of the differences between the measured and expected RMR was statistically different Fig. The concern regarding the possible preservation of the RMR as a consequence of the presence of stressing factors induced by the VLCK-diet and the rapid weight loss was focused by a strict analysis of the protein metabolism.

Although there were some differences in protein status, renal function and nitrogen balance-related parameters, none of them was considered as clinically relevant Table 2.

It is noteworthy that despite the considerable weight loss induced by the VLCK-diet, there was a positive nitrogen balance throughout the entire study. At visit C-2, the positive nitrogen balance was 1. It was not possible to calculate the nitrogen balance at baseline since the protein intake was not assessed at that visit. Besides the FFM, that is considered the major contributing factor, several variables have been described as positive determinants of the RMR, including thyroid hormones, catecholamines, leptin and ketone bodies.

In this study, the level of influence of these mentioned factors on the measured RMR was determined during the study. As Fig. Adrenaline and dopamine did not significantly change during the study, but noradrenaline had a progressive decrease in their plasma levels that reached significant differences at visit C Similarly, leptin values were severely reduced at visit 2, 3 and 4 in accordance with the FM reduction.

Thyroid hormones a , Catecholamines b and Leptin c levels during the study. Changes in Catecholamines; and c. Changes in Leptin. FT3: free triiodothyronine; FT4: tyroxine. The main findings of this work were: 1 the rapid and sustained weight reduction induced by the VLCK-diet did not induce the expected drop in RMR, 2 this observation was not due to a sympathetic tone counteraction through the increase of either catecholamines, leptin or thyroid hormones, 3 the most plausible cause of the null reduction of RMR is the preservation of lean mass muscle mass observed with this type of diet.

The greatest challenge in obesity treatment is to avoid weight recovery sometime after the previous reduction. In fact, after one or few years the most obese patients recover or even increase their weight, previously reduced by either, dietetic, pharmacological or behavioral treatments [ 8 ], bariatric surgery being the only likely exception [ 7 ].

Since obesity reduction is accompanied by a slowing of energy expenditure in sedentary individuals, mostly RMR, this fact has been blamed for this negative outcome of the diet-based treatments [ 12 ]. Therefore any RMR reduction after treatment, translates in a large impact on energy balance, making subjects more prone to weight regain over time [ 17 ].

This phenomenon was called metabolic adaptation or adaptive thermogenesis, indicating that RMR is reduced after weight loss, and furthermore that this reduction is usually larger than expected or out of proportion with the decrease in fat or fat free mass [ 2 ].

Therefore, preservation of initial RMR after weight loss could play a critical role in facilitating further weight loss and preventing weight regain in the long-term [ 4 ]. Although that follow up was not long enough, the finding may be of particular importance for long-term effects. The present work shows that in a group of obese patients treated with a VLCK-diet, the RMR was relatively preserved, remaining within the expected limits for the variations in FFM, and avoided the metabolic adaptation phenomenon.

Because FFM includes total body water, bone minerals and protein [ 14 ], the results were corroborated by analyzing the FFM without bone minerals and total body water muscle mass.

As the mechanisms supporting the metabolic adaptation phenomenon are not known, unraveling the reasons behind the present findings is challenging enough in itself. Changes in any circulating hormone that participate in thermogenesis could be the explanation for the absence of a reduction in RMR, for example a concomitant increase in the sympathetic system activity, either directly or indirectly.

An increase in thyroid hormones generated by the VLCK-diet was discarded because free T3 experienced the well described reduction after losing weight [ 20 , 24 ] without alterations in free T4 or TSH. As thermogenesis in humans is largely a function of the sympathetic nervous system activity, and that activity decreases in response to weight loss the results here reported may be the net result of a maintenance or relative increase in the plasma catecholamine levels.

However, it was found that adrenaline and dopamine remained unchanged throughout the study, while noradrenaline decreased considerably discarding their contribution to any increase in the activity of the autonomic nervous system. Leptin experienced a rapid decline in circulation in situations of weight reduction, although the reduction is observed in energy restriction states it occurs before any change in body weight [ 8 ].

On the other hand, leptin positively has been associated with sympathetic nervous system activity in humans, and weight loss associated changes in RMR and fat oxidation were previously related to leptin levels changes [ 25 ].

If leptin is sensitive to the energy flux and activate the autonomic nervous system, the absence of metabolic adaptation here observed could be due to a leptin increase, or maintenance in the basal levels. However, in this work, leptin levels decreased in accordance to the weight reduction. Then, an expected increase in thyroid hormones, catecholamines, or leptin levels was discarded as explanation for the observed minor or absent reduction in RMR.

This was also endorsed by the undertook multiple regression analysis Table 3. In fact, a clear preservation of FFM was reported in obese subjects on VLCK-diet, in whom 20 kg reduction after 4 months of treatment was accompanied by less than 1 kg of muscle mass lost [ 6 ]. The assumption of muscle mass preservation is also supported by the data on kidney function Table 2 which shows that not only was renal activity not altered as reported in other studies [ 23 ] but that even the nitrogen balance was positive.

The strength of this study is its longitudinal design, which allows the evaluation of the time-course of changes of RMR during a VLCK diet, by comparing each subject to himself, as his own control. The scarce number of subjects and the short duration of this study might be a limitation, since one cannot make claims regarding the RMR status long-term after the completion of the VLCK diet.

However, no significant variations in body weight had been observed after 4 months in previous studies [ 10 , 11 ]. In addition, although participants were instructed to exercise on a regular basis using a formal exercise program, we could not verify adherence to this instruction which precludes determining whether changes in physical activity patterns affected study outcomes. In the current work a portable device that allows for easier measurement of RMR and with lower cost was employed.

This approach may lead to errors when compared with the gold standard, Deltatrac, but it is an easy-to-use metabolic system for determining RMR and VO2 in clinical practice with a better accuracy than predictive eqs.

The Deltatrac device is expensive and requires careful calibration. The Fitmate has been previously validated as a suitable alternative to the traditional indirect calorimetry by both in-house analysis Additional file 1 : Figure S1 , as well as by previous studies.

Despite not measuring CO2 production it is a very convenient in the clinical setting assuming a minimal error of analysis. In summary, this study shows that the treatment of obese patients with a VLCK-diet favors the maintenance of RMR within the expected range for FFM changes and avoids the metabolic adaptation phenomenon. This finding might explain the long-term positive effects of VLCK-diets on weight loss.

Although, the mechanisms by which this effect could be justified are unclear, classical determinants of the energy expenditure, as thyroid hormones, catecholamines as well as leptin were discarded. The relative good preservation of FFM muscle mass observed with this dietetic approach could be the cause for the absence of metabolic adaptation.

Human energy expenditure in affluent societies: an analysis of doubly-labelled water measurements. Eur J Clin Nutr. Evidence for the existence of adaptive thermogenesis during weight loss. Br J Nutr. Scientific opinion on the essential composition of total diet replacements for weight control. The ability to preserve muscle mass or even better, build muscle mass can help preserve our age-related losses.

It might interest you to know that even a lack of sleep i. Thirty years of research demonstrates how the practice of eating very low caloric intakes e. Under this stress, sustained, elevated levels of cortisol can suppress thyroid stimulating hormone production which will ultimately impact thyroid hormones that regulate metabolism. Furthermore, these starvation states can also waste away valuable muscle mass which in turn will also reduce RMR. For more on hormone production and how it pertains to metabolic function , follow the link.

So, how do you gauge whether you are in starvation states where RMR might be negatively impacted? Unless true RMR is known which can set a minimal threshold for daily caloric intake, you might just be guessing with mathematical formulas even though the Mifflin St Jeor is probably the best to use.

An alternative to the BMR formulas is to simply follow the commonly suggested minimal numbers of 1,to-1, calories for women and 1,to-1, calories for men. These numbers, however, provide estimates at best because the macronutrient composition of a diet e.

The sensation of hunger is another viable option to use as a guide, but the sensation of hunger is considered plastic i. Regardless, the hunger scale can help you gain a sense of whether you are providing adequate food calories to your body to avoid starvation — in other words, the opportunity to listen to your body.

Ideally , you would spend your waking hours between hunger scores of 4-and Lastly, take the time to understand some basic differences between hunger and appetite which are outlined below:. Subsequently, we resort to mathematical formulas, but considering their potential errors, the values determined should always be considered a general estimate rather than an accurate value.

Given this, there may also be value in including other methods as a guide to avoiding starvation. Lastly, while we need to acknowledge the fact that RMR is not entirely controllable, there are some influencing factors we can manipulate and should leverage every opportunity to exploit them. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. The American Journal of Clinical Nutrition , 40 1 A new predictive equation for resting energy expenditure in healthy individuals.

The American Journal of Clinical Nutrition , 51 2 Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association , 5 Frankenfield DC, National Heart Lung and Blood Institute. Bethesda: National Institutes of Health, Effect of caloric restriction and excessive caloric intake on energy expenditure. Am J Clin Nutr ; 24 : — Lansky D, Brownell KD. Estimates of food quantity and calories: errors in self-reporting.

Am J Clin Nutr ; 35 : — Long-term effects of dieting on resting metabolic rate in obese outpatients. JAMA ; 6 : — Forbes G. Human Body Composition. New York: Springer-Verlag, Ravussin E, Bogardus C. Relation of genetics, age, and physical fitness to daily energy expenditure and fuel utilization. Am J Clin Nutr ; 49 : — American Dietetic Association. Position of the American Dietetic Association on weight management. J Am Dietetic Assoc ; 97 1 : 71 — Oxford University Press is a department of the University of Oxford.

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Volume Article Contents Introduction. Concluding remarks. Effects of dieting and exercise on resting metabolic rate and implications for weight management. Josephine Connolly , Josephine Connolly. Oxford Academic. Google Scholar. Theresa Romano. Marisa Patruno. Select Format Select format. Permissions Icon Permissions. Introduction The significance of the rising prevalence of obesity for morbidity and associated health care costs is clearly delineated by the United States National Institutes of Health's Clinical Guidelines on the Identification, Evaluation and Treatment of Overweight and Obesity in Adults.

Summary This study examined the effects of three interventions diet; diet and aerobic exercise; diet, aerobic exercise and resistance training on resting metabolic rate and body composition, as well as other physiological and metabolic parameters which are beyond the scope of this review.

Comment The findings regarding no loss of fat-free mass in the diet-only group are surprising, as some degree of obligatory loss of fat-free mass is expected with significant weight loss. Summary This two-part study is based on the assumption that a decrease in calorie intake and weight loss is associated with a decrease in resting metabolic rate and fat oxidation.

Comments In the first part of the study, subjects' resting metabolic rate decreased to a greater extent than their weight or fat-free mass. Summary The authors sought to examine the potential of strength training as a means to prevent the decline in fat-free mass and resting metabolic rate associated with very-low calorie diets.

Comment Dietary factors are addressed in this study in that all meals were provided to patients. Summary It is difficult to summarize the results of studies examining the effect of exercise on resting metabolic rate during a hypocaloric dieting period due to the number of variables that are involved type, duration, frequency and intensity of exercise, degree of energy deficit, total daily calorie intake, and distribution of calories among carbohydrates, proteins and fats.

Comment The use of meta-analysis in this area of research is useful because it allows for a systematic examination of the many variables involved. Concluding remarks Based on the above reviews, we can revisit the controversial issues delineated in the introduction of this paper, and apply these issues to a family physician's practice.

Am J Clin Nutr. J Am Dietetic Assoc. Issue Section:. Download all slides. View Metrics. Email alerts Article activity alert. However, the formula does not take into account all of the factors mentioned above, and as a result, it can under-estimate or over-estimate the RMR. It is important to keep in mind that the equation cannot entirely be relied upon, since each individual is different. For instance, you might find that your actual measured RMR is calories less than your estimated one.

The difference is enough to cause weight gain of several pounds over a few months. The metabolic rate declines with age because of loss of skeletal mass in increased percentage of fat tissue. Your RMR depends on the amount of fat you have. If your body fat percentage is high, your RMR might be lower than that of an individual with a lower body fat percentage. The RMR is lower in women than in men, mostly because men, on average, have a greater muscle mass and a lower body-fat percentage than women.

A smaller body requires fewer calories to maintain the same physiological functions, whereas a larger body requires more calories. Also, during weight loss your body may try to conserve energy in response to a lower calorie intake, this can also cause a reduction in RMR. Taller people typically have greater body surface area and more lean body mass.