Open Access

Reduced postprandial energy expenditure and increased exogenous fat oxidation in young woman after ingestion of test meals with a low protein content

Nutrition & Metabolism20085:25

DOI: 10.1186/1743-7075-5-25

Received: 02 June 2008

Accepted: 17 October 2008

Published: 17 October 2008

Abstract

Background

Macronutrient composition of diets can influence energy balance in humans. We tested the hypothesis whether low protein content in single meals may induce lower values of energy expenditure (EE) and fat oxidation (FO) as compared to adequate protein content.

Methods

Indirect calorimetry was combined with a breath test using naturally 13C-enriched corn oil to differentiate between postprandial exogenous and endogenous FO. Young women ingested single meals containing either 3.9% (low protein, LP) or 11.4% (adequate protein, AP) of total energy (~3100 kJ) as protein.

Results

Postprandial EE was 160 kJ/6 h lower (p < 0.01) after LP meals and diet induced thermogenesis (DIT) increased less (p < 0.001) as compared to AP meals. Total postprandial FO was not significantly different between meals (~17 g/6 h). However, exogenous postprandial FO was significantly (p < 0.01) higher (4.28 ± 1.57 g/6 h) after exposure to LP meals as compared to AP meals (1.87 ± 1.00 g/6 h). Less than 10% of ingested fat (50 g) was oxidized in the postprandial phase. The overall postprandial fat balance was approximately + 33 g.

Conclusion

Breath tests using naturally 13C-labeled corn oil mirror exogenous FO. Low protein meals resulted in reduced postprandial EE and increased exogenous FO as compared to adequate protein meals without differences in total FO.

Background

Obesity is an increasing health problem in both developed and developing countries [1]. Genetic predisposition, physical inactivity, and the consumption of high-energy dense foods are risk factors for obesity [2]. It was shown that diet composition influences energy storage in the body which supported the view that macronutrients may play a role in the development of obesity. However, the results are contradictory and it remains unclear what the relative importance and metabolic advantages of protein, carbohydrate and fat are [3, 4]. Therefore, studies of in vivo effects of macronutrients on body fat storage and metabolism could enhance our understanding of the aetiology of obesity and improve methods for body-weight management.

In order to achieve a reduction in body fat, weight reducing diets must attain a negative energy or fat balance. An increase of the protein content of diets at the expense of carbohydrates has brought such an advantage [46]. Fat oxidation (FO) was shown to depend on dietary composition, being higher after a relatively high protein meal as compared to a balanced diet [7]. Furthermore, there is increasing evidence of higher energy expenditure (EE) following protein ingestion as compared to carbohydrates or fat [812]. However, the mechanisms for the influence of dietary protein on energy expenditure are not clear and controversially discussed [6, 13, 14].

The combination of indirect calorimetry with isotope techniques is an effective tool for the examination of the oxidation of endogenous and ingested nutrients in vivo [1519]. As demonstrated in recent reports 13CO2 breath tests are now widely used in metabolic studies of nutrients using stable isotopic labeled precursors [20, 21]. 10 to 30% of ingested fat were reported to be oxidized postprandially in subjects exposed to different experimental conditions usually using fat supplemented with 13C-labeled fatty acids [1517]. Only few studies were published using 13C-labeled triglycerides as tracers [22]. However, there are no reports in the recent literature available using non supplemented naturally enriched fat such as corn oil to study FO. The use of uniformly labeled naturally enriched fat in metabolic studies may have the advantage of avoiding artefacts due to possible differences in metabolism of artificially with stable isotopes labeled precursors as it was shown e. g. for crystalline amino acids compared to protein-bound amino acids [23]. Therefore, we examined in a pilot study the effects of different test meals with low or adequate protein content and an equal fat content on postprandial EE and substrate oxidation. We hypothesized that an exposure of subjects to test meals with lower protein content may cause reduced rates of EE and FO with possible consequences on energy balance. Exogenous FO was measured using corn oil naturally enriched in 13C-content as the only fat component.

Methods

Subjects

6 healthy young women volunteered for the study (Table 1). They were students from Potsdam University and took part in a traineeship of studies in physiology of nutrition. Participants reported to be non smokers, normo-glycemic, and normo-lipidemic, and free of any endocrine or organ disorders. Furthermore, women were neither pregnant nor lactating and between 3 and 10 d after menstruation. The body mass index (BMI, in kg/m2) was within normal range for all of the subjects and they did not perform any extreme physical activities. Baseline breath 13CO2 enrichments were characteristic for a C3 plant based habitual diet [24]. All subjects volunteered gave an informed consent before participation in the study.
Table 1

General characteristics of the study participants

 

Mean (n = 6) ± SD

Age (y)

25.5 ± 2.6

Weight (kg)

59.8 ± 8.3

Height (m)

1.7 ± 0.1

BMI (kg/m2)

20.6 ± 2.5

Baseline δ13C in breath CO2 [‰ vs. PDB]

-25.8 ± 0.7

Test meals

Composition and sources of the test meals are provided in Table 2 and Table 3. The meals were comparable in energy content but either low (LP, 3.9% of energy) or adequate (AP, 11.4% of energy) in protein content. The terms "low" or "adequate" is based on the Recommended Dietary Allowance for men and women of 0.8 g good quality protein/kg body weight/day. This amount of protein corresponds to about 10% of the energy content of a balanced mixed diet [25]. The carbohydrate content was either 35.4 or 27.8% of energy in the LP or AP test meal, respectively. The total fat content was about 60% of energy in both test meals and consisted practically exclusively of C4 plant based corn oil. 13C abundance of test meal components was determined (Table 2). The low 13C abundance (expressed as δ13C vs. PeeDee Belemnite Limestone carbonate, PDB), see below) of skimmed milk powder showed that animals were not fed with corn based food. Furthermore, the 13C abundance of saccharose is characteristic for beet sugar. Both of these components are C3 plant-based. This is an important condition to measure ingested FO using C4 plant-based naturally 13C-enriched corn oil. As shown previously [26] and tested prior to the beginning of this study, C3 based low 13C meal components have no effect on baseline breath 13CO2 production [Unpublished observations by Petzke]. 13C abundance of corn oil was by about 10 to 12 ‰ δ13C higher than that of the other macronutrient components of the test meals (Table 2). All solid components of each meal were of similar weight (130 g). All components were mixed with water free of carbonic acid to reach a mushy consistency and an equal volume (250 mL). Meals were ingested after baseline measurement of energy expenditure (EE) within 10 min at the beginning of the study at 09:00 to 09:30 h. Additional drinking of mineral water free of carbonic acid was allowed during the study protocol.
Table 2

Composition and sources of test meals

Test meal

 

LP

AP

δ13C [‰ vs. PDB]5

Skimmed milk powder1

(g)

20

60

-28.2 ± 0.7

 

(kJ)

297

895

 

Corn oil2

(g)

50

50

-16.1 ± 0.2

 

(kJ)

1881

1881

 

Wheat starch3

(g)

40

0

-26.9 ± 0.2

 

(kJ)

581

0

 

Saccharose4

(g)

20

20

-27.8 ± 0.2

 

(kJ)

334

334

 

11492 kJ/100 g, Naturaflor®, Töpfer GmbH, Dietmannsried, Germany

23762 kJ/100 g, Mazola®, Unilever Deutschland, Hamburg, Germany

31450 kJ/100 g, Weizella, Hermann Kröner Weizenstärkefabrik, Ibbenbüren, Germany

41668 kJ/100 g, Zucker, Nordzucker, Braunschweig, Germany

5Data are mean values ± SD, n = 5 measurements.

Table 3

Macronutrient composition of test meals1

Test meal

LP

AP

Energy content (kJ)

3114

3131

Protein (g)

7.2

21.0

Protein (kJ)

121

357

Protein (% total energy)

3.9

11.4

Total fat (g)

50.2

50.6

Total fat (kJ)

1890

1903

Total fat (% total energy)

60.7

60.8

Carbohydrate (g)

64.9

51.6

Carbohydrate (kJ)

1102

872

Carbohydrate (% total energy)

35.4

27.8

1Based on calculations using [Food Composition and Nutrition Tables, 5th revised and completed version, compiles by Schertz H and Senser F, medpharm Scientific Publishers, Stuttgart, 1994]

Study protocol and calorimetry

Studies were performed after an overnight (12 h) fast. All participants took part twice and consumed both test meals randomly in a distance of 2 days in between. All subjects underwent measurements of EE using an open-circuit indirect calorimeter with a ventilated-hood system (Deltatrac™ II, Datex Instrumentarium Corp., Helsinki, Finland). The system was calibrated daily according to the instructions using 5% CO2 in O2 calibration gas (QUICK CAL™, GE Healthcare Finland Oy, Helsinki). After a run-in period of 30 min, energy expenditure (EE) was determined between 08:00 and 09:00 within 30 min. Then, subjects ingested the test meals over a period of 10 min and postprandial EE was measured three times after 30, 150, and 270 min of the study protocol. Breath samples were collected 5-fold at baseline (-10 min) and twice every 30 min for a period of 6 h after the meal into tubes (10 mL Exetainer®, Labco Ltd., Buckinghamshire, U.K.) for measurement of breath13CO2 enrichments. The bladder was emptied before the study. During the experimental period within a total time interval of 360 min, complete urine samples were collected for the assessment of nitrogen excretion. Nitrogen content in urine was determined by Kjeldahl method (Kjeldatherm-Turbosog-Vapodest 45, C. Gerhardt GmbH & Co. KG, Bonn, Germany). For each measurement of EE the first 5 to 10 min were discarded to allow subjects to adapt to the measurement procedure, and data from the remaining 20 min were averaged and used to calculate EE and substrate oxidation based on oxygen consumption, carbon dioxide production, and urinary nitrogen excretion.

Stable isotopic analysis

The bulk 13C abundances in food components were determined using an elemental analyser (EA 1108, Fisons Instruments, Rodano, Italy) coupled on-line via a conflo interface to an isotope-ratio mass spectrometer (EA/IRMS; Delta C, Thermo Electron GmbH, Bremen, Germany) as described [27]. Breath 13CO2 enrichments were analysed by isotope ratio mass spectrometry (BreathMAT, Thermo Electron GmbH). Isotopic compositions of carbon are reported in the conventional delta per mill notation in the range of natural abundance expressed in parts per thousand relative to the international standard PDB (δ13C in ‰ vs. PDB) as described [27]:
(1)

where Rstandard = [13C]/[12C] = 0.0112372 for PDB that has been assigned a δ13C value of 0.0‰. Rsample is derived from the ratios of the mass spectrometer ion currents ranging from m/z 44 to m/z 46.

Calculations and statistics

EE (kcal per day) was calculated as
(2)
where VO2 is the oxygen consumption (Liters per day), VCO2 is the CO2 production (Liters per day) and Nex is the urinary nitrogen excretion (grams per day) [28]. Respiratory quotient (RQ) is defined as VCO2 divided by VO2. DIT was calculated by obtaining the increment in postprandial EE above pre-meal baseline values (Table 4) during the measurement period of the protocol as described previously [29]. DIT was expressed in absolute terms (kJ/6 h) and as a percentage of the energy in the test meals. Whole body substrate oxidation rates were calculated before (fasting) and during 6 h after test meal ingestion (postprandial) based on measurements of EE at 30, 150, and 270 min of the study protocol. Net rates of FO, carbohydrate oxidation (CO), and protein oxidation (PO) (in grams per day) were calculated as [30]:
Table 4

Baseline measurements before ingestion of test meals (n = 6)

Test meal

LP

AP

EE (kJ/h)

218 ± 12

230 ± 13

RQ

0.87 ± 0.04

0.86 ± 0.08

PO (g/h)

2.73 ± 0.66

2.73 ± 0.66

FO (g/h)

2.72 ± 1.53

3.05 ± 2.53

CHO (g/h)

10.7 ± 2.9

8.65 ± 4.41

(3)
(4)
(5)
Ingested FO was estimated as reported by Sonko et al. [15, 16] using the following equation:
(6)

where QexFO is the quantity of ingested fat oxidized, δb is the baseline breath 13CO2 abundance (‰ δ13C vs. PDB) δt is the breath 13CO2 abundance at time t post meal ingestion, δt-1 is breath 13CO2 abundance at any other time after t, δs is the 13C abundance of labeled fat ingested, QCO2 is the quantity of CO2 expired in breath (moles) for the time interval in question, MW is the average molecular weight (866 g/mol) of ingested corn oil triglycerides, and n (= 55) is the number of carbon atoms in corn oil triglyceride molecule. 0.56 is the acetate correction factor to account for label fixation that might occur at any step between the entrance of labeled acetyl-CoA into the tricarboxylic acid cycle until the recovery of label in breath CO2 [31].

Data are reported as means ± SD. Comparison of means was performed with two-sided paired t-test. Pearson correlation coefficients were calculated to determine the relationship between selected parameters. Differences with p < 0.05 were considered statistically significant. WinSTAT® (vers. 1999.2, R. Fitch software, Staufen, Germany) was used to compute statistical analysis.

Results

EE and DIT expressed in absolute terms (kJ/6 h) or as percentage of energy in test meals were significantly lower after ingestion of LP meals compared to AP meals (Table 5). There was no change in RQ following both test meals and no significant difference in RQ between different test meals. The relatively high baseline RQ (Table 4) can not be satisfactorily explained. It could be that the overnight fasting period was not sufficient to deplete glycogen stores. Alternatively, the resting period of 30 min before measurement of the resting EE might not have been sufficient for young, healthy normal weight female subjects. As expected, a lower protein intake with the LP meal reduced postprandial PO in relation to fasting levels. On the other hand postprandial PO increased relative to fasting levels following AP meals. The change in PO between test meals was significantly different. Total postprandial CO was not significantly different (p > 0.05) after exposure to different test meals. Total postprandial FO was not significantly different between both test meals. However, postprandial FO slightly increased or decreased as compared to measurements during fasting after exposure to LP or AP meals, respectively. Interestingly, exogenous postprandial FO was significantly higher (p = 0.005) by about 2.4 g/6 h after ingestion of LP meals compared to AP meals. However, the total amount of oxidized exogenous fat during 6 h was relatively low (less than 10% compared to ingested fat mass). On the other hand, endogenous postprandial FO was not significantly different between young woman ingesting LP or AP test meals due to high individual variations. The overall postprandial fat balance was approximately + 33 g. Interestingly, DIT positively correlated with PO (R2 = 0.739, p = 0.011), and exogenous FO negatively correlated with change in PO (R2 = 0.532, p = 0.037).
Table 5

The influence of the test meals on postprandial energy expenditure and substrate oxidation (n = 6)

Test meal

LP

AP

p <

Postprandial EE (kJ/6 h)

1356 ± 69

1516 ± 66

0.01

DIT (kJ/6 h)1

46.5 ± 5.7

134.6 ± 34.3

0.001

DIT (%)

9.0 ± 1.1

25.9 ± 6.6

0.001

RQ

0.87 ± 0.04

0.87 ± 0.03

ns4

Change in RQ

-0.01 ± 0.06

0.01 ± 0.05

ns

Postprandial PO (g/6 h)

14.9 ± 4.20

18.0 ± 4.2

ns

Change in PO (g/6 h)1

-1.50 ± 1.23

1.55 ± 1.29

0.001

Postprandial CO (g/6 h)

55.6 ± 17.8

58.7 ± 14.1

ns

Change in CO (g/6 h)1

-8.70 ± 27.65

6.77 ± 25.34

ns

Postprandial FO (g/6 h)

16.9 ± 7.5

16.8 ± 8.8

ns

Change in FO (g/6 h)1

0.55 ± 7.91

-1.50 ± 7.00

ns

Endogenous postprandial FO (g/6 h)2

12.6 ± 7.8

14.9 ± 9.2

ns

Exogenous postprandial FO (g/6 h)3

4.28 ± 1.57

1.87 ± 1.00

0.01

Contribution of exogenous postprandial FO of energy expenditure (kJ/6 h; % of postprandial EE)

169; 12

74; 5

 

1Calculated as sum of postprandial values over 6 h – (fasting value per h × 6).

2Calculated as exogenous FO – postprandial FO.

3Based on 13CO2 breath test.

4ns = p > 0.05.

Baseline breath δ13CO2 values (Table 1) were similar to those of C3 plant based nutrients (Table 2, [22]). In response to test meal ingestion it was evident that DOB values of breath 13CO2 progressively increased in all subjects (Figure 1). A peak value of 13C enrichment in breath 13CO2 was not reached during 6 h of the study protocol. DOB values increased within 6 h up to 1 or 2 ‰ δ13C after ingestion of AP- or LP-meals, respectively. The δ13C values in breath CO2 of young woman were significantly different (p < 0.05) from 180 min and thereafter comparing between the exposure to LP and AP meals.
Figure 1

Delta value over baseline (DOB) of breath 13 CO 2 of young woman after ingestion of test meals with either 3.9% (LP) or 11.4% (AP) of energy as protein and with naturally enriched corn oil as 13 C source. Data are means ± SD, n = 6. Values with indications are significantly different (*p < 0.05, **p < 0.01, ***p < 0.001). For meal composition and details, see method section.

The time course of cumulative exogenous postprandial FO calculated from δ13CO2 breath values is shown in Figure 2. Cumulative exogenous postprandial FO based on 13CO2 production from corn oil was significantly higher (p < 0.05) as of 270 min and thereafter of young woman exposed to the LP meal as compared to AP meal.
Figure 2

Cumulative exogenous fat oxidation (FO) of young woman after ingestion of test meals with either 3.9% (LP) or 11.4% (AP) of energy as protein and with naturally enriched corn oil as 13 C source. Data are means ± SD, n = 6. Values with indications are significantly different (*p < 0.05, **p < 0.01). For meal composition and details, see method section.

Discussion

In the present pilot study we examined the effect of single ingestions of different test meals with either low or higher but adequate protein content on postprandial energy metabolism and FO in young woman. This was performed to test our hypothesis that an exposure to low protein containing meals may lead to reduced rates of EE and FO as compared to adequate protein meals which may have consequences on energy balance. Our results confirmed that dietary protein may influence postprandial EE and DIT. The postprandial EE was significantly higher in woman after exposure to the AP meal (protein content of 11.4% of energy) as compared to the LP meal (protein content of 3.9% of energy). The value of postprandial EE of young woman was approximately by 160 kJ/6 h higher after exposure to the AP meal as compared to the LP meal. This accounts to approximately 5% of the energy content of test meals. Therefore, the present results confirmed former studies which have shown that protein can induce a higher thermic effect compared to other macronutrients and that high protein diets have a higher potential to increase EE than low protein diets [10, 32, 33]. However, data in literature are not uniform. It was shown under conditions of energy-restriction that a short-term replacement of dietary carbohydrate with protein did not increase the thermic effect of food to facilitate weight loss in type 2 diabetes patients [34]. Moreover, overfeeding of either low- or high-protein diets were found to increase DIT as compared to AP diets [12]. Although, habitual energy intake of young woman was not evaluated in our present pilot study, we assumed no restriction or excess in food energy consumption before test meal consumption. In future studies of postprandial effects of protein consumption an evaluation of the role of previous energy intake will be necessary because food energy deficiency was supposed to prevent thermic effects of dietary proteins [35]. The mechanisms regulating thermic effects after consumption of high protein diets remain to be elucidated. However, based on the prevention of thermic effects in energy deficient states a role of mitochondrial metabolism in modifying energy efficiency may be supposed [35].

In addition, it has been shown that subjects consuming high protein diets (30% of energy) for 4 d exhibited an increased EE and higher rates of FO resulting in lower body fat mass when fed at energy balance and compared to diets containing an adequate protein content (10% of energy) [33, 36]. In the present study we did not find differences in total FO in subjects exposed to LP or AP test meals. Interestingly, exogenous postprandial FO was significantly lower in subjects exposed to AP meals compared to LP meals. It was shown in former studies that net lipid oxidation is dependent on short-term changes in dietary intake, being significantly higher after a high protein meal compared to a meal relatively balanced in macronutrient composition [7]. The reason for lower rates of exogenous FO after exposure to AP meals compared to LP meals is not clear. However, lower rates of gastric emptying after administration of diets containing higher proportions of milk proteins can not be excluded and have to be evaluated in future studies [37]. Taken together, it seems that although able to exhibit higher rates of exogenous FO, meals with a relatively low protein content are not advantageous compared to adequate protein meals with respect of lowering total energy or fat balance.

The measurement of enrichment in expired 13CO2 is widely used to determine nutrient oxidation rates using different infusion techniques or oral consumption of 13C-labeled substrates. Mostly substrates are applied which were exogenously labeled with 13C as fatty acids to enrich the precursor pools by supplementation to fat of test meals to increase the outcome of 13CO2 enrichment in breath samples. However, fatty acids may be metabolized differently than nutrients like fat usually consumed with complex diets. Therefore, intrinsically or naturally enriched tracers should be preferred. Analytical techniques are now sensitive enough to detect relatively small changes of enrichments in the range of natural abundances. Corn oil is naturally enriched (about -16 ‰ δ13C) due to discriminatory accumulation of 13C during photosynthesis. Naturally 13C-labeled triglycerides from corn oil are absorbed and cleaved by lipolysis to 13C-labeled fatty acids and glycerol before incorporation into endogenous fat deposits or subsequent mitochondrial β-oxidation, which results in the production of 13CO2 in breath. Therefore, naturally 13C-enriched corn oil can be used to examine exogenous FO when the subject's habitual diet and test meal components do not contain other corn based products. In the present experiment we have shown that a supplementation of corn oil with 13C-fatty acids was not required. This avoids possible artefacts due to different absorption and metabolism of fatty acids as compared to triglycerides normally available from dietary fat. In addition, no additional assumptions are necessary with respect to not uniformly labeled fatty acids usually supplemented as a tracer. The calculation of exogenous postprandial FO was possible although the mean increase of δ13C values over baseline in breath CO2 amounted to only 1 to 2 ‰ vs. PDB. The method permitted a significant differentiation of effects due to differences in test meal composition on FO. However, it was an essential preposition that baseline values of 13CO2 enrichment did not change during experimental period which we have tested using sunflower seed oil instead of corn oil [Unpublished observations by Petzke].

Conclusion

We have shown that corn oil naturally enriched with 13C can be used to evaluate postprandial FO in vivo. Furthermore, we provide evidence that the amount of dietary protein in relation to other macronutrients may influence postprandial exogenous and endogenous FO the consequences and mechanisms of action of which has to be examined in future studies.

Abbreviations

AP: 

Adequate protein

BMI: 

Body mass index

CHO: 

Carbohydrate oxidation

DIT: 

Diet induced thermogenesis

DOB: 

Delta value over baseline

EE: 

Energy expenditure

EA/IRMS: 

Elemental analyser/isotope ratio mass spectrometer

FO: 

Fat oxidation

LP: 

Low protein

PDB: 

PeeDee Belemnite Limestone carbonate

PO: 

Protein oxidation

RQ: 

Respiratory quotient.

Declarations

Acknowledgements

Petra Albrecht is gratefully acknowledged for excellent technical assistance.

Authors’ Affiliations

(1)
Group of Stable Isotopes and of Energy Metabolism, German Institute of Human Nutrition in Potsdam-Rehbruecke (DIfE)

References

  1. Hedley AA, Ogden CL, Johnson CL, Carroll MD, Curtin LR, Flegal KM: Prevalence of overweight and obesity among US children, adolescents, and adults, 1999–2002. J Am Med Assoc 2004, 291: 2847-2850. 10.1001/jama.291.23.2847View ArticleGoogle Scholar
  2. Hill JO, Melanson EL, Wyatt HT: Dietary fat intake and regulation of energy balance: implications for obesity. J Nutr 2000, 130: 284S-288S.Google Scholar
  3. Astrup A, Grunwald GK, Melanson EL, Saris WH, Hill JO: The role of low-fat diets in body weight control: a meta-analysis of ad libitum dietary intervention studies. Int J Obes Relat Metab Disord 2000, 24: 1545-1552. 10.1038/sj.ijo.0801453View ArticleGoogle Scholar
  4. Schoeller DA, Buchholz AC: Energetics of obesity and weight control: Does diet composition matter? J Am Diet Assoc 2005, 105: S24-S28. 10.1016/j.jada.2005.02.025View ArticleGoogle Scholar
  5. Westerterp-Plantenga MS: The significance of protein in food intake and body weight regulation. Curr Opin Clin Nutr Metab Care 2003, 6: 635-638. 10.1097/00075197-200311000-00005View ArticleGoogle Scholar
  6. Halton TL, Hu FB: The effects of high protein diets on thermogenesis, satiety and weight loss: a critical review. J Am Coll Nutr 2004, 23: 373-385.View ArticleGoogle Scholar
  7. Labayen I, Diez N, Parra D, Gonzales A, Martinez JA: Basal and postprandial substrate oxidation rates in obese woman receiving two test meals with different protein content. Clin Nutr 2004, 23: 571-578. 10.1016/j.clnu.2003.10.004View ArticleGoogle Scholar
  8. Due A, Toubro S, Skov AR, Astrup A: Effect of normal-fat diets, either medium or high in protein, on body weight in overweight subjects: a randomised 1-year trial. Int J Obes Relat Metab Disord 2004, 28: 1283-1290. 10.1038/sj.ijo.0802767View ArticleGoogle Scholar
  9. Mikkelsen PB, Toubro S, Astrup A: Effect of fat-reduced diets on 24-h energy expenditure: comparisons between animal protein, vegetable protein, and carbohydrate. Am J Clin Nutr 2000, 72: 1135-1141.Google Scholar
  10. Johnston CS, Day CS, Swan PD: Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women. J Am Coll Nutr 2002, 21: 55-61.View ArticleGoogle Scholar
  11. Whitehead JM, McNeill G, Smith JS: The effect of protein intake on 24-h energy expenditure during energy restriction. Int J Obes Relat Metab Disord 1996, 20: 727-732.Google Scholar
  12. Stock MJ: Gluttony and thermogenesis revisited. Int J Obes Relat Metab Disord 1999, 23: 1105-1117. 10.1038/sj.ijo.0801108View ArticleGoogle Scholar
  13. Marsset-Baglieri A, Fromentin G, Tome D, Bensaid A, Makkarios L, Even PC: Increasing the protein content in a carbohydrate-free diet enhances fat loss during 35% but not 75% energy restriction in rats. J Nutr 2004, 134: 2646-2652.Google Scholar
  14. Crovetti R, Porrini M, Santangelo A, Testolin G: The influence of thermic effect of food on satiety. Eur J Clin Nutr 1998, 52: 482-488. 10.1038/sj.ejcn.1600578View ArticleGoogle Scholar
  15. Sonko BJ, Prentice AM, Coward WA, Murgatroyd PR, Goldberg GR: Dose-response relationship between fat ingestion and oxidation: quantitative estimation using whole-body calorimetry and 13 C isotope ratio mass spectrometry. Eur J Clin Nutr 2001, 55: 10-18. 10.1038/sj.ejcn.1601112View ArticleGoogle Scholar
  16. Sonko BJ, Fennessey BV, Donelly JE, Bessesen D, Sharp TA, Jacobsen DJ, Jones RH, Hill JO: Ingested fat oxidation contributes 8% of 24-h total energy expenditure in moderately obese subjects. J Nutr 2005, 135: 2159-2165.Google Scholar
  17. Maffeis C, Armellini F, Tato L, Schutz Y: Fat oxidation and adiposity in prepubertal children: Exogenous versus endogenous fat utilization. J Clin Endocrinol Metab 1999, 84: 654-658. 10.1210/jc.84.2.654View ArticleGoogle Scholar
  18. Wallis GA, Dawson R, Achten J, Webber J, Jeukendrup A: Metabolic response to carbohydrate ingestion during exercise in males and females. Am J Physiol Endocrinol Metab 2006, 290: E708-E715. 10.1152/ajpendo.00357.2005View ArticleGoogle Scholar
  19. Mittendorfer B, Fields DA, Klein S: Excess body fat in man decreases plasma fatty acid availability and oxidation during endurance exercise. Am J Physiol Endocrinol Metab 2004, 286: E354-E362. 10.1152/ajpendo.00301.2003View ArticleGoogle Scholar
  20. Stellard F, Elzinga H: Analytical techniques in biomedical stable isotope applications: (isotope ratio) mass spectrometry or infrared spectrometry? Isotopes Environ Health Stud 2005, 41: 345-361. 10.1080/10256010500384333View ArticleGoogle Scholar
  21. Parra MD, Martinez JA: Nutritional aspects of breath testing based on stable isotopes. Nutr Rev 2006, 64: 338-347. 10.1301/nr.2006.jul.338-347View ArticleGoogle Scholar
  22. Metges CC, Wolfram G: Medium and long-chain triglycerides labelled with 13 C: a comparison of oxidation after oral or parenteral administration in humans. J Nutr 1991, 121: 131-136.Google Scholar
  23. Daenzer M, Petzke KJ, Bequette BJ, Metges CC: Whole-body nitrogen and splanchnic amino acid metabolism differ in rats fed mixed diets containing casein or its corresponding amino acid mixture. J Nutr 2001, 131: 1965-1972.Google Scholar
  24. Schmidt H-L, Metges C: Variations of the natural isotope abundance in diet – causes of artifacts or the base of new possibilities in stable isotope tracer work? Clin Nutr Matab Res. Proc 7th Congr ESPEN 1985, 156-168.Google Scholar
  25. German Nutrition Society: Reference values for nutrient intake. Umschau Braus GmbH, Frankfurt am Main, Germany; 2000.Google Scholar
  26. Schoeller DA, Klein PD, Watkins JB, Heim T, MacLean MC: 13 C abundances of nutrients and the effect of variations in 13 C isotopic abundances of test meals formulated for 13 CO 2 breath tests. Am J Clin Nutr 1980, 33: 2375-2385.Google Scholar
  27. Petzke KJ, Boeing H, Metges CC: Choice of dietary protein of vegetarians and omnivores is reflected in their hair protein 13 C and 15 N abundance. Rapid Commun Mass Spectrom 2005, 19: 1392-1400. 10.1002/rcm.1925View ArticleGoogle Scholar
  28. Takala J, Keinänen O, Väisänen P, Kari A: Measurement of gas exchange in intensive care: laboratory and clinical validation of a new device. Crit Care Med 1989, 17: 1041-1047. 10.1097/00003246-198910000-00015View ArticleGoogle Scholar
  29. Piers LS, Soares MJ, Makan T, Shetty PS: Thermic effect of a meal 1. Methodology and variation in normal young adults. Br J Nutr 1992, 67: 165-175. 10.1079/BJN19920020View ArticleGoogle Scholar
  30. Takala Takala J, Meriläinen PT: Handbook of gas exchange and indirect calorimetry. Helsinki: Datex-Ohmeda Inc., Document No. 876710; 1987.Google Scholar
  31. Sidossis LS, Coggan AR, Gastaldelli A, Wolfe RR: A new correction factor for use in tracer estimations of plasma fatty acid oxidation. Am J Physiol 1995, 269: E649-E656.Google Scholar
  32. Tappy L: Thermic effect of food and sympathetic nervous system activity in humans. Reprod Nutr Dev 1996, 36: 391-397. 10.1051/rnd:19960405View ArticleGoogle Scholar
  33. Lejeune MPGM, Kovacs EM, Westerterp-Platenga MS: Additional protein intake limits weight regain after weight loss in humans. Br J Nutr 2005, 95: 281-289. 10.1079/BJN20041305View ArticleGoogle Scholar
  34. Luscombe ND, Clifton PM, Noakes M, Parker B, Wittert G: Effects of energy-restricted diets containing increased protein on weight loss, resting energy expenditure, and the thermic effect of feeding in type 2 diabetes. Diabetes Care 2002, 25: 652-657. 10.2337/diacare.25.4.652View ArticleGoogle Scholar
  35. Petzke KJ, Friedrich M, Metges CC, Klaus S: Long-term dietary high protein intake up-regulates tissue specific gene expression of uncoupling proteins 1 and 2 in rats. Eur J Nutr 2006, 44: 414-421. 10.1007/s00394-004-0545-4View ArticleGoogle Scholar
  36. Lejeune MPGM, Westerterp KR, Adam TCM, Luscombe-Marsh ND, Westerterp-Platenga MS: Ghrelin and glucagons-like peptide 1 concentrations, 24-h satiety, and energy and substrate metabolism during a high-protein diet and measured in a respiration chamber. Am J Clin Nutr 2006, 83: 89-94.Google Scholar
  37. Calbet JA, Holst JJ: Gastric emptying, gastric secretion and enterogastrone response after administration of milk proteins or their peptide hydrolysates in humans. Eur J Nutr 2004, 43: 127-139. 10.1007/s00394-004-0448-4View ArticleGoogle Scholar

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© Petzke and Klaus; licensee BioMed Central Ltd. 2008

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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