Human energy metabolism below, near and above energy equilibrium

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Human energy metabolism below, near and above energy equilibrium

Transcript Of Human energy metabolism below, near and above energy equilibrium

https://doi.org/10.1079/BJN19840111 Published online by Cambridge University Press

British Journal of Nutrition (1984), 52, 429442

429

Human energy metabolism below, near and above energy equilibrium

BY A. J. H. VAN ES, J. E. VOGT, CH. NIESSEN, J. VETH, L. R O D E N B U R G , V. T E E U W S E A N D J. D H U Y V E T T E R Department of Animal Physiology, Agricultural University, Haarweg 10,
6709 PJ Wageningen, The Netherlands
A N D P. D E U R E N B E R G AND J. G. A. J. HAUTVAST Department of Human Nutrition, Agricultural University, De Dreijen 12,
6703 BC Wageningen, The Netherlands
AND E. VAN D E R BEEK Central Institute for Nutrition and Food Research (TNO),P.O. Box 360,
3700 AJ Zeist, The Netherlands

(Received 7 February 1984 - Accepted 22 March 1984)
I . Complete 24 h energy and nitrogen balances were measured for fifteen subjects at three levelsof energy intake and for two other subjects at two levels of intake.
2. At each level, the fifteen subjects ate diets consisting of fifteen to twenty separate foods for 7 or 8 d. Faeces and urine were collected for the final 4 d. Respiratory gas exchange was measured during the final 72 h while the subjects stayed in an 11 ms open-circuit respiration chamber, and simulated office or light household work. The energy balance of the other two subjects was determined initially in a similar way when they consumed a diet which was sufficient for energy equilibrium. Subsequently, the measurements were repeated twice at the same high level of metabolizable energy (ME) intake after 4 and 18 d on that diet.
3. Neither energy nor N digestibilities were significantly affected by intake level or subject. Due to relatively small urinary energy losses the M E content of the gross energy increased slightly a t the higher intake.
4. Respiratory quotient increased with intake level from 0.78 to 0.87. 5. The efficienciesof utilization of ME were approximately 1.O for maintenance (from the low to the intermediate intake level) and decreased to about 0.9 for maintenance and energy deposition (from the intermediate to the high intake level). 6. Estimates of daily ME requirements at energy equilibrium were 149 (SD 13) kJ ME/kg body-weight, 432 (SD 33) kJ ME/kg b o d y - ~ e i g h t ~a'n' ~d 204 (SD 22) kJ/kg lean body mass. The former two values were negatively correlated with percentage body fat although not significantly so. 7. ME utilization and heat production of the other two subjects were nearly equal after 6 and 20 d on a diet supplying 1.5-1.7 times the ME needed for energy equilibrium.

Information on the amount of metabolizable energy (ME) required at energy equilibrium of individuals performing office or light household work is scarce. The same is true for our knowledge of the efficiency of utilization of ME when ingested in amounts smaller or greater than needed for energy equilibrium. Energy balance measurements are well suited to provide such information. However, the number of such measurements lasting 24 h or more is small (Apfelbaum et al. 1971;Agricultural Research Council/Medical Research Council Committees, 1974;Dauncey, 1979,1980; Irsigler et al. 1979;Webb, 1981 ;Ravussin et al. 1982; Schutz et al. 1982). In some of these studies intake of ME was not measured but calculated, the calorimetric rooms used for measurements were small, having a volume of only 5 m3, and room temperatures were sometimes high (see Table 7, p. 440).
The aim of the present study was to obtain more reliable information on 24 h energy metabolism of human adults performing office or light household work during the day and consuming the same diet. The study consisted of three series of experiments (Table 1). In

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A. J. H. V A N Es A N D OTHERS

Table 1. Experimental scheme

Experi-
mental Period. ..
series no. Day of experimental period. . .
1 and 2* Diet ingestion Excreta collection Gas exchange measurement
3 t Period...
Day of experimental period.. .
Level of ME intake Diet ingestion Excreta collection Gas exchange measurement (3 d)

Preliminary (P)

Experimental (E)

1st 2nd 3rd 4th 5th 6th 7th 8th

(+I$+

+ + ++ ++ ++ ++ +++

First

Second

Third

P

E

P

E

P

E

lst-4th 5th-8th 9th-12th 13th-16th 17th-27th 28th-32nd

+ + Intermediate + +

+ High + + +

+ High + + +

ME, metabolizable energy.
* Seven and eight volunteers respectively. t Two volunteers.
$ In series 1, preliminary period of 3 d.

the first series of experiments, energy and nitrogen balances (during days 5-8 on the diet) for sevenvolunteerswere measured far below, slightlybelow and above energy equilibrium. The second series of experiments was a duplication of the first series with eight other volunteers. It was expected that these two series of experiments would provide information on utilization of ME and on diet-induced thermogenesis. Furthermore, the experiments would provide information on the variation in 24 h requirements between subjects. In the third seriesof experimentsthe energy balances of two volunteerswere measured three times, first for 3 d at approximatelyenergy equilibrium after 4 d on the diet, and then after 4 and after 18 d while on a diet supplying 1.5-1.7 times the ME consumed daily in the first week. This third series of experiments was an attempt to test the theory of Garrow (1978) that utilization of ME might change during the course of long periods of high ME intake, which was also discussed by Hervey & Tobin (1983).

MATERIALS AND METHODS
Subjects
Seventeen volunteers (eight females, nine males) aged 18-64 years took part. Before the experiments they were made familiar with experimental procedures and respiration chambers. All were, according to medical examination, in good health. Their body-weights, heights and skinfold thicknesses were measured (Durnin & Womersley, 1974). Specific density was also determined by underwater weighing with correction for lung volume for the subjects of the second and third series of experiments (Table 6, p. 438). While in the respiration chambers, subjects weighed themselves twice daily. None of the subjects smoked tobacco.

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Human energy metabolism

43 1

Diets

The diets were formulated so that they were not very different from a habitual diet but still

could be analysed without difficulties. They consisted of fifteen to twenty foods, each

weighed in daily portions and sampled, providing breakfast, lunch and dinner (to be heated

in hot water) as well as milk, coffee, juice, etc. Some volunteers of experimental series 1 preferred a vegetariandiet, so in their diets meat and meat products were replaced by cheese

and margarine. The approximate energy composition of the diet was; 42% from fat, 13% from protein,
45% from carbohydrate. Thus, the composition of the diet and foods it contained reflected

an average diet in The Netherlands. Bread, margarine and minced meat contributed most

to the energy of the non-vegetarian diets in experimental series 1 and 2; bread, cheese,

minced meat, milk and yoghurt contributed most to the dietary N. For the vegetarian diets

the corresponding items were bread, margarine and cheese, and bread, cheese, milk and

yoghurt respectively.

In principle the diets at each of the three levels of energy intake of experimental series 1 and 2 were of similar composition except that the same daily quantity of vegetables was

used at all levels to supply adequate ‘bulk’. In experimental series 3 at the high level of

intake, in addition to increasing the quantities of several food items, some foods were

included which the subjects liked. A rough estimate of the subjects’usual ME intake at home was obtained by a 3 d weighed

dietary record, including one weekend day. Total ME intake was estimated by using The

Netherlands Foodtables (1981). These estimates and an enquiry on the subjects’ physical

activity formed the basis of their diet at the intermediate level of intake. At the low and high intake levels, 0.5 and 1-5 times as much was ingested respectively. The intermediate

diet was set rather low to ensure that the volunteerswould be able to consumethe high-intake

diet completely. For most ingredients daily portions were weighed for an entire experimental series at a

time. These portions were packed in plastic bags or boxes and stored, if necessary, at low

temperature. Daily portions of beverages and margarine were weighed for a 2-3 d period

1 d before the preliminaryperiod and before and during the main period. Items which might deteriorate during long cold storage were weighed only for two to four experiments at a time. Duplicate samples were taken from each portion just before weighing. For homo-

geneous items like milk, yoghurt an’d apple juice usually only one sample was taken. The vegetables and the minced meat were cooked before sampling and weighing of daily

portions.

Excreta

Total collection of faeces and urine (Table 1) was made during the last 4 d of each experiment after the diet had been eaten for 3 (experimental series l), 4 (experimentalseries 2 and first two experiments of series 3) or 18 d (last experiment of series 3). Excreta were collected several times daily and stored in a refrigerator.

Measurement of respiratory gas exchange
Two open-circuit respiration chambers of 1 1 m3, formerly used for farm animals (Van Es, 1966; Verstegen, 1971), were converted into hotel rooms and equipped with a bed, chair, bicycle home-trainer, wash-stand/writing desk, radio, television set and telephone. Two small airlocks served for the supply of food and removal of excreta. The volume of the air drawn from each chamber was measured by a small dry gas meter. Samples of in- and outgoing air were collected in glass tubes over mercury (composite sample) as well as analysed continuously by a paramagnetic oxygen analyser and an infrared carbon dioxide

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A. J. H. V A N Es AND OTHERS

analyser. The 24 h composite samples were analysed volumetrically with a Sonden apparatus. The results of the physical gas analysesserved to study variations in gas exchange during the 24 h. Heat production was calculated by Brouwer's (1965) equation from 0, consumption, CO, production and urinary N excretion. The composite samples were occasionally analysed also by the infrared analyser or with the Sonden apparatus for methane. At the start and end of each 24 h experiment, samples of chamber air were taken and analysed. The equipment was checked by introducing known quantities of CO, into the chambers. Recovery was 99 (SD 1.5)%. Moreover, the 0, analysis was checked by analysis of fresh outdoor air during each 24 h experiment.
Chamber temperatures were 21 or 22" (depending on the volunteers' wish) from 07.30 to 22.30 hours and 2" lower during the night. Relative humidity was kept at about 70%.
Subjects went to bed at approximately 23.00 hours and rose between 07.30 and 08.00 hours. They ate breakfast, lunch and dinner at about 08.30, 12.30 and 18.00 hours respectively and cycled for approximately 15min at moderate speed on the home-trainer at 08.30 or 08.45, 12.00or 12.15,13.15 or 13.30,17.30and 22.30 hours. They were otherwise free to do what they liked except physical exercise, other than moving occasionally from chair to desk, etc.

Analyses
N in foods and excreta was determined by the Kjeldahl method using mercury as a catalyst (International Organization for Standardization, 1979).
Energy was determined using a static bomb calorimeter. Wet samples were dried first, either by freeze-drying (vegetables, faeces), at room temperature in vacuo (fluids;dried in a polyethylenebag and after drying combusted with the bag) or at 70" in a forced-air drying oven. Samples of cheese, minced meat, sausages and saveloy were mixed with silica gel powder, homogenized and weighed in polyethylene bags. Samples of margarine were also weighed in such bags. Bags with contents were combusted.
All analyses were done at least in duplicate on each sample.

Statistical analysis
Variation in results between subjects was shown by standard deviations. Student's t test, usually for paired observations, was used to see if differences were significant.

Ethics

,

The study was approved by the Ethical Committee of the Department of Human Nutrition

of the Agricultural University.

RESULTS
Diets All dietary items were eaten completely. The coefficients of variation due to sampling and analytical error of the values for energy and N contents used in subsequent calculations
(averages of at least duplicate analyses, usually in two samples) were seldom above 1% .
Variation in energy and N contents of different batches of some items (mincedmeat, cheese, milk, yoghurt, sausage) was greater (up to 3%), so it was necessary to sample and analyse the foods of each new batch, certainly for the items mentioned and preferably for all.
Energy and N losses in faeces and urine Table 2 shows the composition of faeces, digestibilities of energy and N and energy losses in the urine at the three levels of ME intake. The composition of faecal dry matter was fairly constant.

Table 2. Energy and nitrogen in faeces, digestibilities of energy and N , energy in urine and N balance of human subjects at various levels of energy intake

Urine

Faeces

Digestibility

N balance

Experi- Level

kJ as part

5 mental of

DM

kJ/g DM

g N/g DM

Energy

N

kJ/d

of G E

(g/d)

% series energy
no. intake* n Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD

1

L 7 0.25 0.03 21.1

1.0 0.051 0.006 0.920 0.108t 0.825 0.242t 364

36 0.073 0.009 -3.9

0.6

a x

I 8 0.24 0.04 20.5 0.5 0447 0405 0.940 0.005 0.872 0.018 454

51 0.047 0,006 -1.6

1.2

m

2

H 7 0.24 0.03 20.3 0.5 0,047 0,006 0.950 0.011 0.896 0.031 508

55 0.037 0.004 0.6

0.8

L 8 0.27 0.05 21.4 0.5 0.052 0.005 0.938 0,004 0'874 0.018 350

59 0.068 0.009 -3.0

1.2

2

2 I 8 0.23 0.05 20.8 0.4 0,051 [email protected] 0.944 0.007 0.886 0.017 421

74 0.044 0.005 -0.4

1.2

H 8 0.21 0.06 20.8 0.4 0.051 0404 0.940 0.013 0.882 0.025 515

66 0.037 0.005 1.3

1.2

3

z 3

I 1 0.252

20.3

0.048

0.930

0.865

429

I

1 0.243

21.2

0.055

0.898

0.778

583

0,048 0.041

-1.8 - 1.0

8 H, 1 0.231

20.8

0.050

0.917

0.833

492

0.032

2.9

0

5 H, 1 0.244

21.7

0.050

0.921

0.839

656

0.030

4.7

H, 1 0.221

21.0

0.05 1

0.940

0.879

477

0.031

3.6

3

H, 1 0.241

21.8

0.054

0.900

0.786

706

0.032

1.2

L, low; I, intermediate;H, high; DM, dry matter; GE, gross energy; H, and H,, high, second and third periods respectively(see Table 1).
* For details, see p. 431.
t Excluding three atypical values, 0.946 (SD 0.010) for energy and 0,884 (SD0.035) for N.

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A. J. H. V A N Es A N D OTHERS

Irregular defaecation of three of the subjectsat the low intake level in experimental series 1 increased the variation of digestibility (see footnote of Table 2). In further calculations their digestibility values were replaced by the averageenergy and N digestibilities,excluding the extremes, i.e. 0.946 and 0.884 respectively, because the actual values were considered to be due to a short collection period and not to a low digestibility of the diet.
In both experimental series 1 and 2, intake level had no significant effect on the digestibilities of energy and N; also there was no significant variation between subjects.
In the urine, energy content was strongly correlated with N content (P< 0.01). At the low and intermediate energy intakes, N balances (ingested N minus N in faeces and urine)
were negative (Table 2). At the high-intake level some N was retained. This and the high correlation between the N and energy contents of the diets explains why urinary energy losses as a percentage of gross energy (GE) decreased with the higher intake; in absolute terms they increased (Table 2). Since ME is GE minus energy in faeces and urine, the ME content of the ingested energy (ME/GE, Table 3) increased with the higher intake level despite approximately constant energy digestibility.

Combustible gases
Methane production due to microbial conversions in the large intestine was very low or below the detection level. The highest quantity measured in experimental series 1 and 2 was
1 litre/24 h, about 40 kJ. Some subjects tended to produce hardly any methane. In further
calculations energy losses from methane were neglected.

N balances

In view of the short-term nature of the experimental periods, N balances were considered

to have low precision. Moreover, at the low and high intake levels of experimental series

1 and 2 and in the second experiment of series 3, they might not have stabilized because

of the short preliminary period. For these reasons no further attention will be paid to these

balances.

Respiratory gas exchange and calculated heat production

Respiratory quotients (Table 3) were less than 1 and increased with intake level. The diets’

fat content as well as the negative energy balance at the low energy intake, and often at

the intermediate level too (Table 3), were clearly responsible for the low values. At the high

intake, fat deposition caused a further increase.

Daily heat production, calculated from 0, consumption, CO, production and urinary

N, had an average coefficient of variation (%) of 2.8 (SD 1.4) in experimental series 1, and

2.2 (SD 1.5) in experimental series 2 for the same subjects in their 3 d gas exchange

measurement. Usually, despite the overnight stay in the chamber before the start of the

measurement, subjects tended to have a 1-3% higher heat production during the 1st day

of the three consecutivemeasurementsthan during the 2nd and 3rd days. The highest 1st-day

value was found for subjects for whom the chamber and its surroundings were known only

from a few short visitsbefore the experiments.Because differenceswere small,averagevalues

of heat production of all 3 d of one experiment were used in further calculations.

Within subjectsheat production at the intermediate level of intake was only 0.2 (SE 0.05)
MJ/d higher than at the low level (P< 0-01). This is obviously a consequence of

mobilization and utilization of energy of the body reserves at the lower intake with a similar

efficiency of utilization for maintenance purposes as for the diet. According to energy and

N balances, about 90% of the mobilized tissue energy consisted of energy in fat and about

10% in protein. Half the diets’ energy consisted also of fat and protein, the other half was

mostly carbohydrate. Utilization of carbohydrate energy for maintenance purposes is

slightlymore efficientthan that of fat energy because of the greaterpotential of carbohydrate

Table 3 . Metabolizable energy (ME): gross energy (GE), M E intake, energy balance (EB) and respiratory quotient ( R e )of human subjects at various levels of energy intake

ME/W

EB/W

ME/W0'7s

EB/W0'75

Level of

ME/GEt

(kJ/kg)

(kJ/kg)

(kJ/kg)

(kJ/kg)

RQ

Experimental energy

series no.

intake* n Mean

SD

Mean

SD

Mean

SD

Mean

SD

Mean

SD

Mean

SD

Q

1

L

7

0.85

0.11

63

10

-86

9

183

26 -248

23

0.78

0.01

P

(L

4

0.88

0.02)t

3

I

8

0.89

0.01

124

20

-27

8

357

52

- 79

24

0.82

0.02

3

2
3: Subject no. 16 Subject no. 17

H

7

0.91

0.01

175

26

19

14

510

66

55

39

0.85

0.02

(D

: L

8

0.87

0.01

64

12

-75

13

185

33 -219

40

0.78

0.01

$ I

8

0.90

0.01

122

23

-21

16

355

62

-60

48

0.83

0.01

H

8

0.90

0.01

178

32

32

22

518

85

91

62

0.87

0.02

I

1 0.88

146

- 18

396

- 47

0.84

3 2

H,

1 0.88

243

71

663

193

0.90

Q

H,

1 0.91

248

75

679

206

0.88

0-

2 1

1 0.86

144

-4

435

- 12

0.84

8. HI

1 0.89

226

67

688

206

0.90

H*

1 0.87

219

63

669

192

0.90

W, body-weight; W0'75m, etabolic body-weight; L, low; I, intermediate; H, high; H,and H,,high, second and third periods respectively (see Table 1).
* For details, see p. 431. t Excluding three atypical values.

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A. J. H. V A N Es A N D OTHERS

energy for ATP production. The diets, however, had to be digested, the reserves only to be mobilized, so the more efficient utilization of the carbohydrates may have been counteracted by the costs of digestion.
Heat production at the high intake was, within subjects, 0.6 (SD 0-03) MJ more than at
the intermediate level (P< 0-01). Obviously utilization of the ME of the diet for
maintenance and fat deposition was slightly less efficient than for maintenance only, probably due to the costs of conversion of dietary carbohydrate and protein to body fat.
In experimental series 3, heat production increased by 5 and 7% after the change from the intermediate to the high intake level and remained at that level during the next weeks on that level of intake.

Energy balances and M E requirements at energetic equilibrium
Energy balances (EB) were calculated by subtracting heat production from ME intake. Positive EB were found only at the high level of energy intake (Table 3). For better comparison both ME and EB values were divided by either body-weight (W, kg) or metabolic weight (W0.75k, g). Values of the efficiencyof the utilization of ME for maintenance (k,) and for a mixture of maintenance and fat deposition (k,,) were computed from the three or four results of each subject by dividing the difference in EB by the difference in ME intake between the low and intermediate and the intermediate and high intake levels respectively (e.g., k , = (AEB/W)/(AME/W) for the low and intermediate intake levels; k,, = (AEB/W)/(AME/W) for the intermediate and high levels (Table 4)).
The resulting values for k were used in various ways to estimate the ME requirement at energetic equilibrium (ME,) of the subjects of experimental series 1 and 2. The values ME/W or ME/Wo75of experiments with EB values closest to zero for each subject were corrected to values applying to zero balances by subtracting (1/ k )x (EB/W) or ( l / k )x (EB/W0'75).The value of k used was either the value of k , or k,, calculated for each subject or the average value of k , or k,, for all subjects of the same experimental series. Furthermore, a third estimate of ME, was obtained from the regression, for each subject, EB/W or EB/W0'75v. ME/W or ME/Wo'75and calculating the values of ME/W or ME/W0'75for EB/W or EB/Wo'75equal to zero from the regression equation.
The calculated values of k , and k,, were, for experimental series 1, 1.02 (SE 0.05) and 0.85 (SE 0.02) respectively and, for experimental series 2, 0.92 (SE 0.08) and 0.94 (SE 0.03) respectively; for experimental series 3 the values of k,, were 0.90 and 0.87 for subject nos. 16 and 17 respectively. The difference between k , and k,, of experimental series 1 was
significant (P< 0.01). The high standard deviation of k , in experimental series 2 was
probably caused by two subjects who during their experiment at the intermediate intake level showed a high heat production. They were not familiar with the department and it was the first of their three experiments, so they may have had an elevated heat production due to stress. Without their values the estimates of k , and k,, in experimental series 2 were
1.03 (SE 0.03) and 0.91 (SE 0.02) respectively, values which differed significantly (P< 0.01).
Thevaluesofmaintenance ME requirements (kJ/kg) ME,/W, MEm/W0'7a5nd ME,/lean body mass (LBM), calculated by using the subject's own or the average value for k, or the regression method, hardly differed (Table 5). Using the maintenance requirements obtained by regression for all subjects of experimental series 1 and 2, mean values for men and women were separately calculated and were found to be significantly different (P < 0.01) only when expressed as ME,/LBM (Table 5).
The maintenance requirements per W or W0'75were also correlated with body fat content (r -0-45 and -0.53 respectively), with age (r -0.41 and -0.28 respectively) and with height (r -0.21 and -0.03 respectively). Only the correlation with body fat percentage approached significance at the 5% level.

Table 4. Utilization of metabolizable energy (ME) and estimates of M E requirements at energetic equilibriumfor human subjects at various levels of energy intake

Intake levels L and I

Experimental

series no.

n

Mean

SE

Intake levels I and H

Mean

SE

Subject's ownk

Mean

SD

Average k

Mean

SD

Regression

Mean

SD

(a)Relutive to body-weight (W ; kg) k = (AEB/W)/(AME/W)

ME/W for EB = 0

1

7

2

8

3: Subject no. 16 6*

Subject no. 17

I .02

0.05

0.92

0.07

1.02

0.03

0.86

0.02

153

14

153

14

154

0.94

0.03

143

10

142

11

144

0.9 1

0.01

0.91,0.91

166

1641

0.87,0+?9

149

148$

(b) Relutive to mefubolic body-weight (Wa.75;kg) k = (AEB/Wo'7S)/(AME/Wo'5)

ME/WQ'75for EB = 0

5 15

rp

11
4
1

3 2
Q Q-

E?,

1

7

1.01

0.05

2

8

0.92

0.08

6*

1.03

0.03

3: Subject no. 16

Subject no. 17

0.84

0.02

445

30

445

28

446

23

0.94

0.03

415

26

413

28

420

28

0.90

0.02

0.90,0.89

449

443s

0.86,0.87

449

447$

L, low; I, intermediate; H, high; EB, energy balance; k, efficiency of utilization.
* Two atypical values excluded, see p. 436.
't Correction to EB = 0: see p. 436.
$ k=l.

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A. J. H. V A N Es A N D OTHERS

Table 5. Estimates of metabolizable energy (ME) requirements at energetic equilibrium for human subjects (experimental series 1 and 2)
(Mean values and their standard deviations)

~

~~~

~~

ME for
maintenance (ME,) (kJ/kg)

Subject's own k
Mean sD

Average k
Mean SD

Regression Mean SD

6 ( n 8) Mean SD

Q ( n7) Mean SD

MEln/W ME,/W".75
ME,/LBM

148

13

147

13

149

13

150

14

147

14

429

31

428

32

432

33

442

31

421

33

203

22

202

22

204

22

190

13 220** 19

W, body-weight; W0'75,metabolic W; LBM, lean body mass.
Significantly different from value for ME,/LBM for 6: ** P < 0.01.

Table 6. Details of subjects and estimates of their maintenance requirementsfor metabolizable energy (ME) expressed on a body-weight (W) and metabolic body-weight (W0.75b)asis

Experimental Subject

series no.

no.

I

1

2

3

4

5

6

7

Mean (SD)

Wt Height

(kg)

(4

68 62 85 67 75 63 79
71 (9)

1.81 1.63 1.84 1.78 1.75 1.70 1,82
1.76 (7)

Body fat (g/kg)

From skinfolds

From specific density

180

-

300

-

300

-

160

-

380

-

300

-

200

-

260 (80)

Age (years) Sex
28 6 22 P
53 6 22 6 19 P
19 P 55 6
31 (16)

Maintenance requirement

ME/W (kJ/kg)

MEf wo"5 (kJ/kg)

170* 165 133 159 137 167 144
154 (15)

490* 464 405 456 404 474 43 1
446 (34)

2

8

69

1.75

200

150

41

6

163

472

9

16

1.67

400

420

61

P

133

393

10

74

1.64

400

420

64

P

139

407

11

56

1.71

270

230

24

P

147

403

12

84

1.91

220

200

31

8

132

400

13

69

1.74

(250)t 230

24

P

1 40

405

14

77

1.81

(200)t

180

53 i3 145

430

15

73

1 .so

220

220

57

6

155

453

Mean (SD) 72 (8) 1.75 (9) 270 (80)

44 (17)

144 (11) 420 (28)

3

16

53

1.66

-

200

23 P

1643

4433

17

84

1.81

-

130

25

d

1483

4473

* Obtained by the regression method.
t Estimated from density; skinfold value not measured. 3 Energy utilization (k) = 1.

The maintenance requirements of subjectsnos. 16and 17 of experimentalseries 3 derived from their measurement at the intermediate level using a k , of 1.0 were (kJ/kg) 164 and 148 ME/W, 443 and 447 ME/W0.'IS,and 205 and 170 ME/LBM respectively.
Table 6 shows details of the subjects and their estimated maintenance requirements; in Fig. 1 the values ME/Wo'75are plotted against the values EB/W0'75for all seventeen
subjects.
SubjectsEnergyValuesIntakeDiet