Changes In Body Energy Stores Research Articles

Effect of Sleep Extension on Objectively Assessed Energy Intake Among Adults With Overweight in Real-life Settings

Short sleep duration has been recognized as a risk factor for obesity. Whether extending sleep duration may mitigate this risk remains unknown. To determine the effects of a sleep extension intervention on objectively assessed energy intake, energy expenditure, and body weight in real-life settings among adults with overweight who habitually curtailed their sleep duration. This single-center, randomized clinical trial was conducted from November 1, 2014, to October 30, 2020. Participants were adults aged 21 to 40 years with a body mass index (calculated as weight in kilograms divided by height in meters squared) between 25.0 and 29.9 and had habitual sleep duration of less than 6.5 hours per night. Data were analyzed according to the intention-to-treat principle. After a 2-week habitual sleep period at baseline, participants were randomized to either an individualized sleep hygiene counseling session that was intended to extend their bedtime to 8.5 hours (sleep extension group) or to continue their habitual sleep (control group). All participants were instructed to continue daily routine activities at home without any prescribed diet or physical activity. The primary outcome was change in energy intake from baseline, which was objectively assessed as the sum of total energy expenditure and change in body energy stores. Total energy expenditure was measured by the doubly labeled water method. Change in body energy stores was computed using regression of daily home weights and body composition changes from dual-energy x-ray absorptiometry. Sleep duration was monitored by actigraphy. Changes from baseline were compared between the 2 groups using intention-to-treat analysis. Data from 80 randomized participants (mean [SD] age, 29.8 [5.1] years; 41 men [51.3%]) were analyzed. Sleep duration was increased by approximately 1.2 hours per night (95% CI, 1.0 to 1.4 hours; P < .001) in the sleep extension group vs the control group. The sleep extension group had a significant decrease in energy intake compared with the control group (-270 kcal/d; 95% CI, -393 to -147 kcal/d; P < .001). The change in sleep duration was inversely correlated with the change in energy intake (r = -0.41; 95% CI, -0.59 to -0.20; P < .001). No significant treatment effect in total energy expenditure was found, resulting in weight reduction in the sleep extension group vs the control group. This trial found that sleep extension reduced energy intake and resulted in a negative energy balance in real-life settings among adults with overweight who habitually curtailed their sleep duration. Improving and maintaining healthy sleep duration over longer periods could be part of obesity prevention and weight loss programs. ClinicalTrials.gov Identifier: NCT02253368.

An objective measure of energy intake using the principle of energy balance.

The measurement of energy intake is central to the understanding of energy balance and predicting changes in body weight. Until recently, the most commonly used methods of assessing intake were self-reported diet recalls, diet diaries, or food-frequency questionnaires. These methods, however, are subject to systematic biases and are often inaccurate. Review the validations and applications of an expenditure/balance method for measuring energy intake. Review the literature regarding the theory and practice of objectively measuring energy intake based on the principle of energy balance i.e., energy intake is calculated from the measured total energy expenditure plus the change in body energy stores (ES). The attainable precision is modeled and compared with the accuracy and precision of validations against known energy intake. Measurement of energy intake, calculated in this way, is accurate to within 2% and has a precision of 4-37% depending on the expenditure and body composition methods used and the time interval between measures. Applications of this expenditure/balance (EB) method have provided novel data on the compliance to dietary restriction and its association with physical activity interventions, and the effects of bariatric surgery on energy intake and weight gain. Practical limitations to this method, however, include cost and limited access to the analyses required by the DLW method. The EB method of objectively measuring energy intake is objective, accurate, and reasonably precise. It is practical for moderate-sized studies.

Leptin and the maintenance of elevated body weight.

Obesity represents the single most important risk factor for early disability and death in developed societies, and the incidence of obesity remains at staggering levels. CNS systems that modulate energy intake and expenditure in response to changes in body energy stores serve to maintain constant body adiposity; the adipocyte-derived hormone leptin and its receptor (LEPR) represent crucial regulators of these systems. As in the case of insulin resistance, a variety of mechanisms (including feedback inhibition, inflammation, gliosis and endoplasmic reticulum stress) have been proposed to interfere with leptin action and impede the systems that control body energy homeostasis to promote or maintain obesity, although the relative importance and contribution of each of these remain unclear. However, LEPR signalling may be increased (rather than impaired) in common obesity, suggesting that any obesity-associated defects in leptin action must result from lesions somewhere other than the initial LEPR signal. It is also possible that increased LEPR signalling could mediate some of the obesity-associated changes in hypothalamic function.

Validation of an inexpensive and accurate mathematical method to measure long-term changes in free-living energy intake

Accurate measurement of free-living energy intake (EI) over long periods is imperative for understanding obesity and its treatment. Unfortunately, traditional methods rely on self-report and are notoriously inaccurate. Although EI can be indirectly estimated by the intake-balance method, this technique is prohibitively labor-intensive and expensive, requiring repeated measures of energy expenditure via doubly labeled water (DLW) along with multiple dual-energy X-ray absorptiometry (DXA) scans to measure changes in body energy stores. Our objective was to validate a mathematical method to measure long-term changes in free-living energy intake. We measured body weight and EI changes (ΔEI) over 4 time intervals by using the intake-balance method in 140 individuals who underwent 2 y of caloric restriction as part of the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy study. We compared the ΔEI values calculated by using DLW/DXA with those obtained by using a mathematical model of human metabolism whose only inputs were the initial demographic information and repeated body weight data. The mean ΔEI values calculated by the model were within 40 kcal/d of the DLW/DXA method throughout the 2-y study. For individual subjects, the overall root mean square deviation between the model and DLW/DXA method was 215 kcal/d, and most of the model-calculated ΔEI values were within 132 kcal/d of the DLW/DXA method. Accurate and inexpensive estimates of ΔEI that are comparable to the DLW/DXA method can be obtained by using a mathematical model and repeated body weight measurements.

Estimating energy expenditure in mice using an energy balance technique

To compare, in mice, the accuracy of estimates of energy expenditure (EE) using an energy balance technique (TEEbal: food energy intake and body composition change) vs indirect calorimetry (TEEIC). In 32 male C57BL/6J mice, EE was estimated using an energy balance (caloric intake minus change in body energy stores) method over a 37-day period. EE was also measured in the same animals by indirect calorimetry. These measures were compared. The two methods were highly correlated (r(2)=0.87: TEEbal=1.07*TEEIC-0.22, P<0.0001). By Bland-Altman analysis, TEEbal estimates were slightly higher (4.6±1.5%; P<0.05) than TEEIC estimates (Bias=0.55 kcal per 24 h). TEEbal can be performed in 'home cages' and provides an accurate integrated long-term measurement of EE while minimizing potentially confounding stress that may accompany the use of indirect calorimetry systems. The technique can also be used to assess long-term energy intake.

Approaches for quantifying energy intake and %calorie restriction during calorie restriction interventions in humans: the multicenter CALERIE study.

Calorie restriction (CR) is a component of most weight loss interventions and a potential strategy to slow aging. Accurate determination of energy intake and %CR is critical when interpreting the results of CR interventions; this is most accurately achieved using the doubly labeled water method to quantify total energy expenditure (TEE). However, the costs and analytical requirements of this method preclude its repeated use in many clinical trials. Our aims were to determine 1) the optimal TEE assessment time points for quantifying average energy intake and %CR during long-term CR interventions and 2) the optimal approach for quantifying short-term changes in body energy stores to determine energy intake and %CR during 2-wk DLW periods. Adults randomized to a CR intervention in the multicenter CALERIE study underwent measurements of TEE by doubly labeled water and body composition at baseline and months 1, 3, and 6. Average %CR achieved during the intervention was 24.9 ± 8.7%, which was computed using an approach that included four TEE assessment time points (i.e., TEE(baseline, months 1, 3, and 6)) plus the 6-mo change in body composition. Approaches that included fewer TEE assessments yielded %CR values of 23.4 ± 9.0 (TEE(baseline,) months 3 and 6), 25.0 ± 8.7 (TEE(baseline,) months 1 and 6), and 20.9 ± 7.1% (TEE(baseline, month 6)); the latter approach differed significantly from approach 1 (P < 0.001). TEE declined 9.6 ± 9.9% within 2-4 wk of CR beginning and then stabilized. Regression of daily home weights provided the most reliable estimate of short-term change in energy stores. In summary, optimal quantification of energy intake and %CR during weight loss necessitates a TEE measurement within the first month of CR to capture the rapid reduction in TEE.

A computational model to determine energy intake during weight loss

Energy intake (EI) during weight loss is difficult and costly to measure accurately. The objective was to develop and validate a computational energy balance differential equation model to determine individual EI during weight loss. An algorithm was developed to quantify EI during weight loss based on a validated one-dimensional model for weight change. By using data from a 24-wk calorie-restriction study, we tested the validity of the EI model against 2 criterion measures: 1) EI quantified through food provision from weeks 0-4 and 4-12 and 2) EI quantified through changes in body energy stores [measured with dual-energy X-ray absorptiometry (DXA)] and energy expenditure [measured with doubly labeled water (DLW)] from weeks 4-12 and 12-24. Compared with food provision, the mean (±SD) model errors were 41 ± 118 kcal/d and -22 ± 230 kcal/d from weeks 0-4 and 4-12, respectively. Compared with EI measured with DXA and DLW, the model errors were -71 ± 272 kcal/d and -48 ± 226 kcal/d from weeks 4-12 and 12-24, respectively. In every comparison, the mean error was never significantly different from zero (P values > 0.10). Furthermore, Bland and Altman analysis indicated that error variance did not differ significantly over amounts of EI (P values > 0.26). Almost all individual participants' values were within CI limits. The validity of the newly developed EI model was supported by experimental observations and can be used to determine an individual participant's EI during weight loss.

Examination of Cognitive Function During Six Months of Calorie Restriction: Results of a Randomized Controlled Trial

Calorie restriction increases longevity in many organisms, and calorie restriction or its mimetic might increase longevity in humans. It is unclear if calorie restriction/dieting contributes to cognitive impairment. During this randomized controlled trial, the effect of 6 months of calorie restriction on cognitive functioning was tested. Participants (n = 48) were randomized to one of four groups: (1) control (weight maintenance), (2) calorie restriction (CR; 25% restriction), (3) CR plus structured exercise (CR + EX, 12.5% restriction plus 12.5% increased energy expenditure via exercise), or (4) low-calorie diet (LCD; 890 kcal/d diet until 15% weight loss, followed by weight maintenance). Cognitive tests (verbal memory, visual memory, attention/concentration) were conducted at baseline and months 3 and 6. Mixed linear models tested if cognitive function changed significantly from baseline to months 3 and 6, and if this change differed by group. Correlation analysis was used to determine if average daily energy deficit (quantified from change in body energy stores) was associated with change in cognitive test performance for the three dieting groups combined. No consistent pattern of verbal memory, visual retention/memory, or attention/concentration deficits emerged during the trial. Daily energy deficit was not significantly associated with change in cognitive test performance. This randomized controlled trial suggests that calorie restriction/dieting was not associated with a consistent pattern of cognitive impairment. These conclusions must be interpreted in the context of study limitations, namely small sample size and limited statistical power. Previous reports of cognitive impairment might reflect sampling biases or information processing biases.

Assessment of energy status in hill sheep using computer tomography

Breeding leaner sheep is a desirable goal provided reductions in fatness do not compromise survival and productivity, particularly in harsh environments. Whether some energy stores are more labile than others, the internal fat depots in particular, is not clear. Genetic variation in this trait could be usefully exploited in hill sheep where carcass fat is undesirable but energy reserves are important. Patterns of change in body energy stores need to be examined to determine when it is best to assess energy stores in animals. X-ray computer tomography (CT) provides a means to examine depletion and repletion of body energy but scans are not cheap. In order to use CT in a cost effective way, a number of variables need to be assessed from just a few scans. This report presents results of a study designed to define such a scanning approach in terms of which scans were most informative and which produced most accurate predictions of tissue size.

Energy expenditure and requirement while climbing above 6,000 m.

Humans survive the low barometric pressure of altitudes above 6,000 m only by making a complex series of adaptations. However, the effects of such adaptations on energy metabolism have not been widely studied. To determine daily energy requirement at extreme altitude, energy expenditure (EE) was measured by doubly labeled water (DLW) and energy intake-balance (IB) methods in five men and one woman while climbing between 5,900 and 8,046 m over a 7-day period. Energy intakes were determined by dietary record (13.8 +/- 2.0 MJ/day). Change in body energy stores, estimated from differences in body weight, skinfold thickness, limb circumference, and isotope-dilution techniques, was -5.1 +/- 1.6 MJ/day. DLW (19.4 +/- 1.2 MJ/day) and IB (18.9 +/- 2.7 MJ/day) measurements of EE provided similar estimates of group mean EE. These results suggest that IB and DLW techniques can yield comparable estimates of group mean EE at extreme altitude. It is concluded that problems of meeting energy requirements while climbing at extreme altitude are related to energy intakes amounting to only roughly 70% of EE.

Estimation of energy requirements in persons with severe central nervous system impairment

We measured resting metabolic rate (RMR) in 12 persons (aged 10 to 30 years) with severe impairment of the central nervous system requiring gastrostomy feedings, and compared our findings with the RMR predicted from standardized equations. The RMR was 70.6% ± 15.7% of that predicted from the Mayo Clinic nomogram, 63.7% ± 18% of that predicted from the Food and Agriculture Organization/World Health Organization/United Nations University equation, and 75.4% ± 17.3% of that predicted from the Robertson and Reid equation. Energy intake was 756 ± 225 kcal/day and RMR was 708 ± 231 kcal/day; RMR adjusted for changes in body energy stores was 729 ± 231 kcal/day. No significant differences were found between energy intake and RMR, or between energy intake and the sum of RMR and changes in body energy stores. These findings demonstrate that standardized equations overestimate energy needs of individuals with severe CNS impairment. Measures of energy intake adjusted for weight changes represent a valid method to determine energy requirements in a group of individuals with severe CNS impairment. Length was found to be significantly correlated with RMR ( r = 0.79; p <0.01). When the regression equation was tested on another group of subjects from the same residential facility, the equation predicted energy needs reasonably well for those individuals with similar energy intakes but not for all patients with CNS disorders. (J P EDIATR 1995;126:828-32)

A new method for the estimation of the components of energy expenditure in patients with major trauma.

The management of critically ill patients would be better understood if the total energy expenditure (TEE) and its components are known. To quantify the different components of energy expenditure in patients with major trauma, we used a technique combining measurements of body composition and oxygen consumption. We determined changes in body weight, total body water, total body protein, total body potassium, total body fat, and bone mineral content every 5 days over a 10-day period in a group of nine multiply injured patients. Resting energy expenditure was measured by indirect calorimetry (REEm), and a predicted value was obtained from total body potassium (REEp). TEE was assessed by adding the total calorie intake to the changes in body energy stores, and the activity energy expenditure (AEE) was calculated by subtracting REEm from TEE. Mean daily values for REEm, REEp, TEE, and AEE were 2,236 +/- 140, 1,683 +/- 82, 3,029 +/- 276, and 793 +/- 213 kcal/day, respectively, over the 10-day study period. Although not statistically significant, the mean AEE was four times smaller for the first 5 days of study than for the second 5 days (298 +/- 400 vs. 1,254 +/- 588 kcal/day). The technique of combining indirect calorimetry and body composition measurements offers a new approach to evaluate energy expenditure and a new way to study metabolic disorders and therapeutic strategies in critically ill patients.

Total energy expenditure of healthy Swedish women during pregnancy and lactation

Total energy expenditure (TEE) was estimated in healthy Swedish women by the doubly labeled water method in a longitudinal study during pregnancy and lactation. Measurements were made before pregnancy (A); in gestational weeks 16-18 (B), 30 (C), and 36 (D); as well as 2 (F) and 6 (G) mo after delivery. When the results were interpreted, earlier published data regarding resting metabolic rate (RMR), energy intake, and energy in breast milk were also considered. TEE (MJ/d) and TEE/RMR were 10.5 +/- 2.2 (mean +/- SD) and 1.87 +/- 0.42 (n = 28), 9.6 +/- 2.8 and 1.65 +/- 0.67 (n = 22), 12.5 +/- 3.4 and 1.82 +/- 0.45 (n = 22), 12.2 +/- 4.1 and 1.66 +/- 0.52 (n = 19), 10.6 +/- 2.0 and 1.82 +/- 0.41 (n = 23), and 10.8 +/- 2.7 and 1.79 +/- 0.42 (n = 23) at A, B, C, D, F, and G, respectively. The results indicated that physical activity tended to be decreased during early pregnancy. Taking changes in body energy stores into consideration, it was estimated that subjects recorded 86% and 77% of their energy intakes at A and F respectively.

Doubly labeled water measurement of human energy expenditure during strenuous exercise

The energy expenditures (EE) of 23 adult male Marines were measured during a strenuous 11-day cold-weather field exercise at 2,200- to 2,550-m elevation by both doubly labeled water (2H2 18O, DLW) and intake balance methods. The DLW EE calculations were corrected for changes in baseline isotopic abundances in a control group that did not receive 2H2 18O. Intake balance EE was estimated from the change in body energy stores and food intake. Body energy-store changes were calculated from anthropometric [-1,574 +/- 144 (SE) kcal/day] and isotope dilution (-1,872 +/- 293 kcal/day) measurements made before and after the field exercise. The subjects kept daily logbook records of ration consumption (3,132 +/- 165 kcal/day). Mean DLW EE (4,919 +/- 190 kcal/day) did not differ significantly from intake balance EE estimated from food intake and either anthropometric (4,705 +/- 181 kcal/day) or isotope dilution (5,004 +/- 240 kcal/day) estimates of the change in body energy stores. The DLW method can be used with at least the same degree of confidence as the intake balance method to measure the EE of active free-living humans.

Validity of reported energy intake in obese and nonobese adolescents

Daily metabolizable energy intake (ME) and total daily energy expenditure (TEE) were measured in 28 nonobese and 27 obese adolescents over a 2-wk period. Reported ME was significantly (p less than 0.001) lower than measured TEE in both the nonobese and the obese groups (2193 +/- 618 vs 2755 +/- 600 kcal/d and 1935 +/- 722 vs 3390 +/- 612 kcal/d, respectively). Reported ME as a percentage of TEE was significantly lower in the obese than the nonobese group (58.7 +/- 23.6% vs 80.6 +/- 18.7%, respectively). When reported ME was adjusted to account for changes in body energy stores, reported ME still remained significantly lower than TEE in both groups. ME was highly reproducible over the 2-wk period. Intraclass correlation coefficients among days for subjects with complete 14-d diaries were 0.87 and 0.89 for nonobese and obese groups, respectively. In both groups, interindividual variability in ME was significantly greater than intraindividual variability. Our data suggest that reported ME in nonobese and obese adolescents is not representative of TEE or energy requirements.

Use of the doubly labeled water method for measurement of energy expenditure, total body water, water intake, and metabolizable energy intake in humans and small animals.

The basis of the doubly labeled water method is measurement of the differential rates of disappearance of two isotopes of water (H2 18O and either 2H2O or 3H2O, administered at the start of the study) from body water. Published studies indicate that, in its current forms, this technique can be used to provide accurate and reasonably precise information on carbon dioxide production, total body water, and water intake in free-living humans and many small animals. Total energy expenditure can be calculated from carbon dioxide production with little loss of precision. Metabolizable energy intake can also be predicted, as the sum of total energy expenditure plus an estimate for the change in body energy stores during the measurement, but this prediction is unlikely to be accurate and precise unless the subject is in approximate energy balance.

Accuracy of heart-rate monitoring and activity diaries for estimating energy expenditure

The accuracy of heart-rate monitoring and activity diaries for measuring energy expenditure in free-living individuals was studied in 12 women. Estimates of energy expenditure were calculated from heart-rate monitoring by use of four different prediction equations to describe the relationship between heart rate and energy expenditure. Estimates of energy expenditure from activity diaries were calculated using both individually measured and published values for the energy cost of activities. Energy intake adjusted for changes in body-energy stores was used as a reference. Heart-rate monitoring overestimated group energy expenditure from 2 to 9% and the errors in estimating individual energy expenditure ranged from -53 to 67%. Activity diaries underestimated group energy expenditure by 2-6% and the errors in estimating individual energy expenditure ranged from -39 to 56%. Heart-rate monitoring and activity diaries may prove useful for estimating the energy expenditure of groups but not individuals.

Validation of doubly labeled water for measuring energy expenditure during parenteral nutrition

The doubly labeled water method was compared with intake-balance for measuring energy expenditure in five patients receiving total parenteral nutrition (TPN). Because parenteral solutions were isotopically different from local water, patients had to be placed on TPN at least 10 days before the metabolic period. Approximately 0.1 g 2H2O and 0.25 g H218O per kg total body water were given orally. We collected saliva before, 3 h, and 4 h after the dose for measurement of total body water and urine before, 1 day, and 14 days after the dose for measurement of isotope eliminations. On day 14, total body weight was remeasured and change in body energy stores was calculated, assuming constant hydration. Intake was assessed from weights of TPN fluids plus dietary record for any oral intake. Energy expenditure from doubly labeled water (±SD) averaged 3 ± 6% greater than intake-balance. Doubly labeled water method is a noninvasive, nonrestrictive method for measuring energy expenditure in patients receiving TPN.