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Medium-Chain Triglycerides Increase Energy Expenditure and Decrease Adiposity in Overweight Men

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The objectives of this study were to compare the effects of diets rich in medium-chain triglycerides (MCTs) or long-chain triglycerides (LCTs) on body composition, energy expenditure, substrate oxidation, subjective appetite, and ad libitum energy intake in overweight men. Twenty-four healthy, overweight men with body mass indexes between 25 and 31 kg/m(2) consumed diets rich in MCT or LCT for 28 days each in a crossover randomized controlled trial. At baseline and after 4 weeks of each dietary intervention, energy expenditure was measured using indirect calorimetry, and body composition was analyzed using magnetic resonance imaging. Upper body adipose tissue (AT) decreased to a greater extent (p < 0.05) with functional oil (FctO) compared with olive oil (OL) consumption (-0.67 +/- 0.26 kg and -0.02 +/- 0.19 kg, respectively). There was a trend toward greater loss of whole-body subcutaneous AT volume (p = 0.087) with FctO compared with OL consumption. Average energy expenditure was 0.04 +/- 0.02 kcal/min greater (p < 0.05) on day 2 and 0.03 +/- 0.02 kcal/min (not significant) on day 28 with FctO compared with OL consumption. Similarly, average fat oxidation was greater (p = 0.052) with FctO compared with OL intake on day 2 but not day 28. Consumption of a diet rich in MCTs results in greater loss of AT compared with LCTs, perhaps due to increased energy expenditure and fat oxidation observed with MCT intake. Thus, MCTs may be considered as agents that aid in the prevention of obesity or potentially stimulate weight loss.
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Medium-Chain Triglycerides Increase Energy
Expenditure and Decrease Adiposity in
Overweight Men
Marie-Pierre St-Onge,* Robert Ross,† William D. Parsons,* and Peter J.H. Jones*
Abstract
ST-ONGE, MARIE-PIERRE, ROBERT ROSS, WILLIAM
D. PARSONS, AND PETER J.H. JONES. Medium-chain
triglycerides increase energy expenditure and decrease
adiposity in overweight men. Obes Res. 2003;11:395–402.
Objective: The objectives of this study were to compare the
effects of diets rich in medium-chain triglycerides (MCTs)
or long-chain triglycerides (LCTs) on body composition,
energy expenditure, substrate oxidation, subjective appetite,
and ad libitum energy intake in overweight men.
Research Methods and Procedures: Twenty-four healthy,
overweight men with body mass indexes between 25 and 31
kg/m
2
consumed diets rich in MCT or LCT for 28 days each
in a crossover randomized controlled trial. At baseline
and after 4 weeks of each dietary intervention, energy
expenditure was measured using indirect calorimetry, and
body composition was analyzed using magnetic resonance
imaging.
Results: Upper body adipose tissue (AT) decreased to a
greater extent (p 0.05) with functional oil (FctO) com-
pared with olive oil (OL) consumption (0.67 0.26 kg
and 0.02 0.19 kg, respectively). There was a trend
toward greater loss of whole-body subcutaneous AT volume
(p 0.087) with FctO compared with OL consumption.
Average energy expenditure was 0.04 0.02 kcal/min
greater (p 0.05) on day 2 and 0.03 0.02 kcal/min (not
significant) on day 28 with FctO compared with OL con-
sumption. Similarly, average fat oxidation was greater (p
0.052) with FctO compared with OL intake on day 2 but not
day 28.
Discussion: Consumption of a diet rich in MCTs results in
greater loss of AT compared with LCTs, perhaps due to
increased energy expenditure and fat oxidation observed
with MCT intake. Thus, MCTs may be considered as agents
that aid in the prevention of obesity or potentially stimulate
weight loss.
Key words: body composition, magnetic resonance im-
aging, energy expenditure, medium-chain triglycerides,
weight loss
Introduction
The prevalence of overweight and obesity has been in-
creasing worldwide. In the U.S., the prevalence of over-
weight has increased from 25.4% to 33.3% in the adult
population from National Health and Nutrition Examination
Study II to phase I of National Health and Nutrition Exam-
ination Study III (1,2). Therefore, it is apparent that strate-
gies designed to prevent or treat obesity are of paramount
importance. Medium-chain triglycerides (MCTs)
1
have
been proposed previously as a tool in the prevention of
human obesity (3,4) due to their effects on fat deposition in
animals. When compared with long-chain triglyceride
(LCT) consumption, MCTs are known to increase energy
expenditure (EE) in humans (5–11) and are associated with
lower body weight (BW) gain and fat depot size (3,4,12,13)
in growing animals. Recent findings (10,14), however, have
failed to demonstrate convincing results regarding the long-
term benefits of MCT consumption on BW in humans.
From our previous research in women (9,10), there is
evidence to support the hypothesis that women do not
respond to MCT intake as strongly as men. In fact, previ-Received for review July 23, 2002.
Accepted in final form November 21, 2002.
*School of Dietetics and Human Nutrition, McGill University, Ste-Anne-de-Bellevue,
Quebec, Canada and †School of Physical and Health Education, Queen’s University,
Kingston, Ontario, Canada.
Address correspondence to Peter J.H. Jones, School of Dietetics and Human Nutrition,
21111 Lakeshore Rd., Ste-Anne-de-Bellevue, Quebec, Canada H9X 3V9.
E-mail: jonesp@macdonald.mcgill.ca
Copyright © 2003 NAASO
1
Nonstandard abbreviations: MCT, medium-chain triglyceride; EE, energy expenditure;
BW, body weight; LCT, long-chain triglyceride; OL, olive oil; VAS, visual analog scale;
CNRU, Clinical Nutrition Research Unit; FctO, functional oil; MRI, magnetic resonance
imaging; AT, adipose tissue; LT, lean tissue; TEF, thermic effect of food; PP, postprandial;
RMR, resting metabolic rate.
OBESITY RESEARCH Vol. 11 No. 3 March 2003 395
ously published studies that have been conducted in men
(5,7,8) report greater differences in EE between MCT and
LCT consumption than those observed by our group when
studying women (9,10). Because long-term controlled feed-
ing studies examining the effects of MCTs on EE and body
composition have not been conducted in men, the present
objective was to assess whether feeding men diets rich in
MCT or olive oil (OL), as a source of LCT, would result in
greater EE and weight loss after 4 weeks. We hypothesized
that MCT consumption would result in greater EE and
weight loss compared with OL over a 28-day feeding pe-
riod. In addition, it is suggested that MCT consumption may
lead to increased levels of satiety and, thus, lower caloric
ingestion than with LCT consumption (1518). Therefore, a
secondary objective was to determine if appetite ratings on
a visual analog scale (VAS) and food intake at an ad libitum
intake lunch session would be altered by the type of fat
contained in the diet.
Research Methods and Procedures
Subjects
Subjects were recruited by advertisement in local news-
papers and were required to have a body mass index be-
tween 25 and 31 kg/m
2
and fasting plasma total cholesterol
and triglycerides concentrations below 7.0 mmol/L and 3.0
mmol/L, respectively. Exclusion criteria were reported his-
tory of cardiovascular disease, diabetes, hypertension, gas-
trointestinal disorders, and unusual eating patterns. The
study protocol was reviewed and accepted by the Human
Ethical Review Committee of the Faculty of Agriculture
and Environmental Sciences of McGill University, and all
subjects signed informed consent forms before entrance into
the protocol.
Study Design
The study employed a randomized crossover controlled
feeding design with periods of 28 days each, separated by a
4-week washout period. The research was conducted at the
Mary Emily Clinical Nutrition Research Unit (CNRU) of
McGill University. Subjects were required to come to the
CNRU every morning for breakfast and to return to con-
sume one other meal under supervision at the CNRU every
day. The third meal was prepared and packed for the sub-
jects to consume outside of the unit. Diets were designed to
resemble a typical North American diet and contained 40%
of energy as fat, 15% as protein, and 45% as carbohydrates.
The two different diets were consumed in random order for
a period of 4 weeks each, separated by a 4-week washout
period. These diets were identical except for the quality of
the fat. The MCT-containing diet contained a functional oil
(FctO) composed of 64.7% MCT oil (Neobee 1053, Stepan
Company, Northfield, IL), 12.6% OL, 6.8% each of canola
and flaxseed oil, and 5.8% coconut oil as the main source of
fat (75% of total fat). The control diet (OL) contained 75%
of total fat as OL. The rest of the fat came from the other
foods in the meals that were identical in both diets. The fatty
acid composition of the FctO is provided in Table 1. The
FctO also contained 3.4% of unesterified stanol/sterol mix-
ture (Forbes Medi-Tech, Vancouver, Canada) because pre-
vious studies have shown increased plasma lipid concentra-
tions with MCT consumption (6,18,20). Lipid level data
were obtained and form the basis for a complementary
manuscript currently under consideration for publication.
Energy intake was calculated on an individual basis using
the Mifflin equation (21) and an activity factor of 1.7. This
activity factor was shown to be appropriate for weight
maintenance (22) and has been used by our group previ-
ously (9,10). During the 1st week of the first experimental
phase, energy intake was adjusted to compensate for any
change in BW that may have occurred. However, after this
initial 1-week period, energy intake was kept constant
throughout both experimental phases. Meals were isoener-
getic and were provided in a 3-day rotating cycle menu.
Subjects were instructed to consume all foods provided to
them and nothing else for the duration of the trial. They
were also advised to maintain a regular exercise pattern
throughout the trial in accordance with habitual levels.
Methods
BW was measured every morning before breakfast using
a standard scale. Body composition was assessed using
magnetic resonance imaging (MRI) on days 1 and 29 of
each experimental phase. The MRI protocol is described in
detail elsewhere (10). Briefly, images were acquired using a
Siemens 1.5 Tesla MRI scanner (Siemens, Mississauga,
Canada) using a T-1 weighted, spin-echo sequence with a
210-ms repetition time and a 17-ms echo time. Subjects lay
in the magnet in a prone position with their arms straight
Table 1. Fatty acid composition of the functional oil
Fatty acid Functional oil (%)
6:0 0.17
8:0 36.95
10:0 30.35
12:0 3.61
14:0 1.06
16:0 3.52
16:1 0.23
18:0 0.65
18:1 13.81
18:2n-6 4.62
18:3n-3 4.94
20:0 0.05
MCT, Energy Expenditure, and Body Composition, St-Onge et al.
396 OBESITY RESEARCH Vol. 11 No. 3 March 2003
above their head. Using the intervertebral space between the
fourth and fifth lumbar vertebrae as the point of origin,
transverse images with 10-mm slice thickness were ob-
tained every 40 mm from hand to foot, resulting in a total of
45 images for each subject. MRI data were analyzed using
specially designed image analysis software (Tomovision
Inc., Montreal, Canada). Details of the data analysis proce-
dure have been published previously (10).
It is reported that the mean difference for repeat measure-
ments of whole-body adipose tissue (AT) and lean tissue
(LT) was 3% and 2%, respectively (23), and the mean
difference for subcutaneous and visceral AT at the fourth
and fifth lumbar vertebrae was 1.1% and 5.5%, respectively
(24). Thus, MRI measures the different AT compartments
with an error of estimate of 2% to 10% (25). More recently,
Mitsiopoulos et al. (26) determined the reproducibility of
MRI subcutaneous AT volume measurements by comparing
the intra- and interobserver estimates for MRI measure-
ments and found that these were 2.9 1.2% and 1.5
1.5% for intra- and interobserver variability of subcutane-
ous AT, respectively. Results from our group showed intra-
observer differences of 2.1 1.2% for total, 1.8 1.1% for
subcutaneous, and 8.1 3.9% for visceral AT when com-
paring two analyses of five MRI datasets by a single ob-
server (10).
EE was measured with a metabolic monitor (Delta Trac,
Sensor Medics, Anaheim, CA) on days 2 or 3 and 27 or 28
for 19 of the subjects. After an overnight warm-up period,
the metabolic monitor was calibrated daily using gas con-
taining 96% O
2
and 4% CO
2
at ambient pressure. Expired
gases were analyzed against ambient air. Subjects were
required to arrive at the CNRU 1 hour before the start of the
measurement period to allow for their metabolism to return
to a state that approximated basal state. EE was then mea-
sured for 30 minutes before consumption of a standard
breakfast. Subjects were required to consume the breakfast
within a 30-minute period, after which EE measurements
resumed for 5.5 h. This length of monitoring was recom-
mended previously to capture most of the thermic effect of
food (TEF) (27). EE was measured for 30 minutes of each
hour after breakfast. Fat and carbohydrate oxidation rates
were calculated every minute using the equations derived by
Lusk (28).
Total fecal samples were collected over 3 days midway
through each experimental phase for 19 of the subjects for
determination of fecal fat excretion. Samples were weighed
and diluted by 50% with water, aliquoted, and lyophilized.
Fecal lipids were extracted from 3 g of the combined
3-day dried samples, with each day of sampling being
proportionately represented. Lipid extraction was carried
out using the method of Folch et al. (29) in duplicate. The
lipid fraction was then weighed and used to calculate total
fecal fat excretion over 3 days.
Total daily EE was calculated using the following
equation:
Total EE energy intake
( total AT ⫹⌬LT energy excreted)
where AT represents total energy stored in AT mass, and LT
represents total energy stored in LT mass. Energy stored in
AT was determined by multiplying the change in AT vol-
ume by 0.92 g/cm
3
(30) and further multiplying by 7650
kcal/kg, assuming that 85% of AT is fat (31). To determine
energy stored in LT, the change in LT volume was multi-
plied by 1.04 g/cm
3
(30) and again by 2920 kcal/kg, assum
-
ing 73% hydration of LT (32). Both values were then
divided by 28 to obtain daily values. Energy excreted was
determined as the product of daily fecal fat excretion mul-
tiplied by 9 kcal/g of fat.
For a subgroup of 5 subjects, for whom we did not
measure EE and fecal fat excretion but who were part of the
main group of 24 subjects, we tested the effects of FctO and
OL on satiety and food intake. Subjects were required to
rank their level of satiety by answering six questions on a
validated VAS (33) immediately after (0 hours), at 2 hours,
and at 4 hours after consuming a standard breakfast con-
taining either FctO or OL. Questions included in the VAS
were: 1) how hungry do you feel?; 2) how full do you feel?;
3) how strong is your desire to eat?; 4) how much do you
think about food?; 5) urge to eat; and 6) preoccupations with
thoughts on food. Subjects were asked to place a mark on a
continuous scale from 0 to 10, where 0 meant not at all
and 10 meant very much. After answering the last ques-
tionnaire (4 hours), subjects were given foods, which did
not contain the test fats, in excess of their expected food
intake and were instructed to consume as much of these
foods as they wanted until they felt satiated. The amount of
food consumed at this ad libitum lunch session was mea-
sured and energy and macronutrient intakes analyzed using
Food Processor Nutrition Analysis Software (version 7.81,
ESHA Research, Salem, OR).
Statistical Analyses
The effect of each diet on EE and substrate oxidation was
analyzed using ANOVA with a mixed model procedure.
Diet, day, and hour were tested as variables in the model.
Interactions between diet and day and among diet, day, and
hour were also examined. Paired Students t test was used to
determine differences in EE between FctO and OL at each
time-point. Paired Students t test was used to assess dif-
ferences between FctO and OL on average postprandial
(PP) EE, average TEF, average PP fat oxidation, calculated
total daily EE, changes in body composition, fecal fat ex-
cretion, and food intake during the satiety test. ANOVA was
used to assess differences between treatments in response to
questions on the VAS. Diet, hour, and diet-by-hour inter-
MCT, Energy Expenditure, and Body Composition, St-Onge et al.
OBESITY RESEARCH Vol. 11 No. 3 March 2003 397
actions were used as variables in the model. All statistical
analyses were conducted using SAS statistical software
(SAS/STAT version 8.0, SAS Institute, Cary, NC). A p
value of 0.05 was taken as statistically significant. Data are
reported as means SEM.
Results
Twenty-five of the 30 men enrolled in the study success-
fully completed the protocol. Three subjects were asked to
withdraw from the study due to poor compliance, one with-
drew due to medical reasons unrelated to the trial, and one
withdrew for work-related reasons. Data from one subject
were not analyzed due to difficulties with the acquisition of
images during the last MRI scan. Subject characteristics at
recruitment are shown in Table 2.
BWs at endpoint were lower than at baseline for both
FctO (p 0.001) and OL (p 0.05) feeding periods. BWs
were 87.4 2.0 kg at baseline and 86.3 1.9 kg at the end
of the FctO feeding period and were 86.6 2.0 kg and
85.9 1.8 kg at baseline and at the end of the OL feeding
period, respectively. Weight loss occurred gradually over
the entire 28-day period for both FctO and OL feeding
periods. Table 3 shows changes in BW and body composi-
tion values with FctO and OL consumption. Using MRI to
assess body composition changes, there was a significant
decrease (p 0.01) in total body mass from 70.2 1.6 kg
on day 1 to 69.2 1.5 kg on day 29 with FctO consump-
tion, whereas the change from 69.5 1.5 kg to 69.0 1.5
kg with OL consumption was not statistically significant.
Total AT masses were 24.7 1.0 kg and 23.9 1.1 kg on
days 1 and 29, respectively, with FctO consumption (p
0.01, within diet difference) and 24.3 1.0 kg and 24.0
1.0 kg on days 1 and 29, respectively, with OL consump-
tion. There was a trend (p 0.087) for greater loss of total
subcutaneous AT with FctO compared with OL consump-
tion. FctO consumption resulted in a significant decrease
(p 0.01) from 18.1 0.9 kg to 17.6 0.9 kg in
subcutaneous AT. With OL consumption, subcutaneous AT
mass varied from 17.8 0.9 kg on day 1 to 17.7 0.9 liters
on day 29. When regional adiposity was analyzed, there was
greater (p 0.05) loss of upper body AT with FctO con-
sumption compared with OL. FctO consumption resulted in
a decrease (p 0.05) in upper body AT from 12.5 0.6 kg
on day 1 to 11.8 0.6 kg on day 29. Upper body AT masses
were 12.1 0.6 liters on days 1 and 29 during OL feeding.
Abdominal and lower body AT volumes were not altered by
FctO or OL consumption. There was no difference in
change in muscle mass and LT mass between FctO and OL
consumption. Changes in body composition with FctO con-
sumption were not correlated with initial body mass index.
Resting metabolic rate (RMR) was not different between
periods of FctO and OL consumption. Average RMR with
FctO consumption was 0.82 0.02 kcal/min on day 2 and
0.80 0.03 kcal/min on day 28, and with OL consumption,
RMR was 0.81 0.02 kcal/min on day 2 and 0.83 0.02
kcal/min on day 28.
Figure 1 shows basal and PP EE on days 2 and 28. There
was a significant effect of diet (p 0.01) and hour (p
0.01) on EE. Average PP EE tended to be greater (p
0.055) with FctO consumption compared with OL for both
days 2 and 28. On day 2, average PP EE was 1.04 0.02
kcal/min and 0.99 0.03 kcal/min for FctO and OL con-
sumption, respectively. On day 28, average PP EE was
1.01 0.02 kcal/min after consumption of the breakfast
containing FctO, compared with 0.98 0.03 kcal/min for
OL. Average TEF was calculated as the difference between
average PP EE and RMR. On day 2, TEF with FctO con-
sumption was 0.21 0.02 kcal/min compared with 0.19
0.01 kcal/min with OL consumption. For day 28, TEF after
consumption of the breakfast containing FctO was greater
Table 2. Subject characteristics at screening
Characteristic Average (SEM)
Age (y) 43.1 (2.3)
Weight (kg) 87.2 (1.9)
Height (m) 1.76 (0.01)
Body mass index (kg/m
2
)
28.2 (0.4)
Total cholesterol (mmol/L) 5.62 (0.18)
Triglyceride (mmol/L) 1.86 (0.15)
Table 3. Change in body weight and body compart-
ment volumes with functional oil and olive oil con-
sumption
Body compartment
Functional oil
(SEM)
Olive oil
(SEM)
Body weight (kg) 1.03 (0.25) 0.62 (0.29)
Total adipose tissue (kg) 0.83 (0.25)* 0.31 (0.30)
Subcutaneous adipose
tissue (kg) 0.54 (0.16)* 0.17 (0.19)
Upper body adipose
tissue (kg) 0.67 (0.26)* 0.02 (0.19)
Abdominal adipose
tissue (kg) 0.17 (0.13) 0.07 (0.08)
Lower body adipose
tissue (kg) 0.24 (0.21) 0.27 (0.16)
* Significant within-diet change, p 0.05, using paired Students
t test.
Significantly different from change with olive oil consumption,
p 0.05, using paired Students t test.
MCT, Energy Expenditure, and Body Composition, St-Onge et al.
398 OBESITY RESEARCH Vol. 11 No. 3 March 2003
(p 0.01) than that observed after the breakfast containing
OL. After consumption of the FctO-containing breakfast,
TEF was 0.21 0.01 kcal/min vs. 0.15 0.02 kcal/min for
the OL-containing breakfast.
Average EE over the entire measurement period, from
RMR until 6.5 hours after breakfast, was greater (p 0.05)
with consumption of the breakfast containing FctO com-
pared with OL on day 2, although this was no longer
significant for day 28. Average EE was 1.00 0.02 kcal/
min with FctO consumption and 0.96 0.03 kcal/min with
OL consumption on day 2, and 0.98 0.02 kcal/min with
FctO intake and 0.95 0.03 kcal/min with OL intake on
day 28. Using Equation 1 to calculate total daily EE, we
found that EE during FctO consumption was 3169.7
125.8 kcal/d and 3050.9 114.6 kcal/d during OL
consumption.
Figure 2 shows basal and PP fat oxidation on days 2 and
28. There was a significant effect of diet (p 0.01), hour
(p 0.01), and diet-by-hour interaction (p 0.01) on fat
oxidation. Basal fat oxidation was not different between
phases of FctO and OL consumption. On day 2, basal fat
oxidation was 0.054 0.004 g/min and 0.055 0.003
g/min with FctO and OL consumption, respectively. Simi-
larly, on day 28, basal fat oxidation was 0.055 0.003
g/min with FctO and 0.056 0.004 g/min with OL con-
sumption. Average PP fat oxidation was greater (p 0.052)
after consumption of the breakfast containing FctO com-
pared with the breakfast containing OL, but this difference
was not present on day 28 (p 0.32). Fat oxidation after the
FctO-containing breakfast was 0.052 0.003 g/min vs.
0.044 0.003 g/min after the OL-containing breakfast. On
day 28, average fat oxidation was 0.049 0.003 g/min and
0.047 0.003 g/min after the FctO- and the OL-containing
breakfasts, respectively.
Fecal fat excretion was similar between FctO consump-
tion and OL. Average fecal fat recovery was 0.481 0.05
g/d with FctO intake and 0.334 0.04 g/d with OL intake.
This represents 99.6% and 99.7% fat absorption for peri-
ods of FctO and OL consumption, respectively.
There was no effect of diet, but a significant effect of
hour, on hunger and satiety perceptions using the VAS.
Also, there was no significant interaction between diet and
hour on responses to the questions on the VAS. However,
there was a trend (p 0.062) toward lower energy intake at
Figure 1: EE after consumption of a breakfast containing OL or
FctO on day 2 (A) and 28 (B). FctO phase (closed squares), OL
phase (open squares). Values are means SEM, n 19. FctO
significantly different from OL, p 0.05 (*). Trend for diet
difference, p 0.1 (**).
Figure 2: Fat oxidation after consumption of a breakfast contain-
ing OL or FctO on day 2 (A) and 28 (B). FctO phase (closed
squares), OL phase (open squares). Values are means SEM, n
19. FctO significantly different from OL, p 0.05 (*). Trend for
diet difference, p 0.1 (**).
MCT, Energy Expenditure, and Body Composition, St-Onge et al.
OBESITY RESEARCH Vol. 11 No. 3 March 2003 399
the ad libitum lunch session after the breakfast containing
FctO compared with the session after OL breakfast con-
sumption. This was mostly due to lower (p 0.05) fat
consumption at the ad libitum lunch session after the FctO
breakfast compared with the one after the OL breakfast.
Discussion
This study shows, for the first time, that when consumed
as part of a strictly controlled targeted weight maintenance
diet, an FctO rich in MCT leads to greater loss of AT stores
compared with a diet rich in LCT. This change in total
adiposity may be due to a rise in EE and fat oxidation with
FctO consumption relative to a diet rich in LCT in the form
of OL.
Results obtained in this trial on body composition are in
contrast with those obtained previously in women, which
showed no significant effect of MCT consumption com-
pared with LCT on total adiposity (10). Differences in MCT
and LCT consumption on EE between men and women may
be due to hormonal differences or, more likely, to differ-
ences in intakes. Men generally consume more calories than
women and, therefore, would have a greater absolute intake
of MCT.
Although the magnitude of the difference observed in
total AT reduction between diets contrast, our results agree
with those of Tsuji et al. (14), who found greater body fat
loss with MCT compared with LCT supplementation in
their overweight subgroup. Reasons for discrepancies in
results likely include differences in study design. Because
the study by Tsuji et al. (14) was a supplementation trial, it
is possible that subjects consuming the MCT supplement
altered their diet or spontaneously consumed fewer calories
than those supplemented with LCT. In addition, the dose of
MCT given was low (10 g) to produce such an effect on
body composition (14). Also, our results are similar to those
of Matsuo et al. (34), who found that subjects supplemented
with structured MCT gained less body fat than subjects
supplemented with LCT over a 12-week period. However,
in this trial, intakes were not strictly controlled and, as in the
trial by Tsuji et al. (14), the dose of MCT supplied was low.
The use of MRI in this study allowed determination of
small variations in tissue volumes and is a well-established
method for measuring total and regional adiposity because
contiguous slices are acquired (23,35). The accuracy of
MRI in assessing body fat compartments has been demon-
strated previously (23,24). Therefore, we are confident that
the changes observed are biological and not due to meth-
odological error.
When extrapolating average measured EE to total daily
EE, the difference in EE between FctO and OL feeding
periods represents 63 kcal/d on day 2 and 43 kcal/d on day
28. This is slightly lower than observed by Scalfi et al. (7)
and Dulloo et al. (8), who have reported differences in daily
EE between MCT and LCT consumption of 86 and 120
kcal/d. However, when we calculated total EE based on the
difference between energy intake and energy output, we
found a difference of 119 kcal/d (not significant) between
FctO and OL consumption. Differences between previous
results (7,8) and those obtained in the present trial may be
due to differences in the quantities of MCT provided in the
diet. In this trial, subjects consumed an average of 21.5 g of
MCT per meal compared with 30 g for the previous trials
(7,8). Furthermore, it is possible that MCTs exert more
profound increments in EE when given in a single acute
ingestion than during chronic ingestion. Our results and
those of White et al. (9) support the idea that the initial
increase in EE with MCT consumption compared with LCT
is lessened when measured again after 14 days (9) and 28
days, as observed with diminished statistical power on day
28 in this trial. Nevertheless, the extent of increase in EE
observed in this trial can explain the differences in BW
change between FctO and OL phases. When daily EE is
extrapolated over a 28-day period, the total difference in EE
would lead to differences in BW change between the two
diets of 0.36 to 0.51 kg, when using EE values measured on
days 28 and 2, respectively.
Fat absorption was 99.6% with FctO consumption, which
is similar to that observed in an animal trial comparing the
digestibility of different types of fat (36). Also, earlier
studies of the absorbability of fats in rats showed that
coconut oil, which is rich in MCT, is 99.7% absorbed (37).
With OL consumption, fat absorption was measured to be
99.7%, which is greater than the 97.4% absorption rate
reported by Jones et al. (38) for oleic acid. However, OL
also contains 11.4% of fatty acids as linoleic acid (39),
which was found to be 99.4% absorbed (38).
Our data on subjective satiety and ad libitum intake at
lunch, although collected on only a small number of
subjects, extend and support existing literature. Data ob-
tained using VAS to assess perceived satiety showed no
difference between FctO and OL phases, as was observed
by VanWymelbeke et al. (16) when comparing OL, lard,
MCT oil, and a fat substitute, and by Bendixen et al. (11)
when comparing the effects of modified fats containing
medium chain fatty acids with rapeseed oil. The use of the
VAS to assess satiety sensations has been shown to be
reproducible under controlled conditions and with the use of
subject designs (40).
Bendixen et al. (11) also found no difference in ad libitum
food intake with consumption of modified fats compared
with the rapeseed oil. This is in contrast with what was
observed in this trial and that of others (15,16). We found a
strong trend toward lower energy intake of 221 kcal at the
lunch after the breakfast containing FctO compared with the
breakfast containing OL. VanWymelbeke et al. (16) found
differences in energy intakes between MCT and OL diets of
43 kcal, whereas in a subsequent study, the same group (17)
found that subjects consumed 129 kcal less at a meal after
MCT, Energy Expenditure, and Body Composition, St-Onge et al.
400 OBESITY RESEARCH Vol. 11 No. 3 March 2003
MCT consumption compared with LCT. Similarly, Stubbs
and Harbron (15) found differences in daily energy intakes
of 258 kcal between a diet containing large amounts of
MCTs compared with that containing the least amount of
MCT, when food intakes were precisely recorded.
In conclusion, we have shown that consumption of a diet
rich in MCT for 28 days improves adiposity, particularly
upper body adiposity in overweight men. This may be due
to enhanced EE and fat oxidation compared with OL con-
sumption and to greater fecal fat excretion. In addition,
there was a strong trend toward lower spontaneous energy
intake at the free lunch session after a standard breakfast
rich in MCT, compared with one rich in OL. Therefore, it is
possible that, under free-living conditions, subjects would
consume less energy and fat when their diet contained MCT
and, thus, would obtain this added benefit to increased EE,
resulting in better weight maintenance and possibly weight
loss. Therefore, future studies should be conducted on a
free-living population, replacing the major source of added
fat in the diet with MCTs for a period of 6 months and
comparing with a control group consuming an oil rich in
LCTs. This design would allow all aspects of MCT con-
sumption, increased EE, and satiety to exert their effect and
possibly produce beneficial changes in body composition.
Results from the present trial suggest that MCTs may be
considered as a potential tool in the prevention of weight
gain and obesity.
Acknowledgments
Funding was provided by Dairy Farmers of Canada and
Forbes Medi-Tech Inc. We acknowledge the help of Chris
Vanstone for the processing of fecal samples, the staff of the
Mary Emily Clinical Nutrition Research Unit for assistance
in meal preparation, Cathy Tucci for help in recruitment
of subjects, and Lindsay MacKinnon for help with MRI
analyses.
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There are a number of procedures for estimating predicted energy needs of study participants on controlled diets, one of which involves approximating basal metabolic rate using the Mayo Clinic Food Nomogram and multiplying by a factor representing activity needs. The factor 1.7 was used to predict energy needs of eight young men receiving a liquid diet for three 10-day periods and six receiving conventional foods for one 16-day period. Subjects active in athletics received additional compensatory energy, thus increasing the factor to 1.8 to 1.9. Absolute net weight change was small, averaging 0.41±0.26 percent body weight for the first study and 0.67±0.69 percent for the second study. Subjects' weight patterns support the use of this procedure for energy prediction.
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Energy intake, weight gain, carcass composition, plasma hormones and fuels, hepatic metabolites and the activities of phosphoenolpyruvate carboxykinase (PEPCK), malic enzyme, and glucose 6-phosphate dehydrogenase (G6P-DH) were examined in adult rats during a 44-day period of low fat, high carbohydrate (LF) feeding or of consumption of one or two high (70% metabolizable energy) fat diets composed of 63% (metabolizable energy) long-chain (LCT) or medium-chain (MCT) triglycerides. Energy intake was similar in the LCT and MCT groups but was less than that of LF group. The weight gain of rats fed MCT diet was 30% less than that of rats fed LF or LCT diets. Energy retention was less when the diet provided MCT than LCT or LF, and that resulted in a 60% decrease in the daily lipids deposition. Plasma glucose, free fatty acids, glycerol, and insulin/glucagon ratio were similar in the three groups. Blood ketone body (KB) concentrations in rats fed the high fat diets were extremely elevated, particularly in the MCT group, but declined throughout the experiment and by the 44th day hyperketonemia decreased by 50% but remained higher than in the LF diet. The blood beta-hydroxybutyrate/acetoacetate (B/A) ratio remained slightly elevated in rats fed the high fat diets. Similar changes were observed in liver KB concentration and in the B/A ratio. Liver lactate/pyruvate ratio elevated in the LCT and MCT groups at the initiation of the diets decreased by 50% at the end of the experiment. The consumption of high fat diets led to a 1.5-fold increase in liver PEPCK activity.(ABSTRACT TRUNCATED AT 250 WORDS)