Effects of short-term carbohydrate or fat overfeeding on energy expenditure and plasma leptin concentrations in healthy female subjects

Abstract

To determine the effects of excess carbohydrate or fat intake on plasma leptin concentrations and energy expenditure.
Ten healthy lean females were studied: (a) during a 3 day isoenergetic diet (ISO); (b) during 3 day carbohydrate overfeeding (CHO OF); and (c) during 3 day fat overfeeding (FAT OF). During each test, basal metabolic rate, the energy expended during mild physical activity and recovery, and 24 h energy expenditure (24 h EE) were measured with indirect calorimetry. The concentrations of glucose and lactate were monitored in subcutaneous interstitial fluid over a 24 h period using microdialysis. Plasma hormone and substrate concentrations were measured in a blood sample collected in the morning of the fourth day.
CHO OF increased plasma leptin concentrations by 28%, and 24 h EE by 7%. Basal metabolic rate and the energy expended during physical activity were not affected. FAT OF did not significantly change plasma leptin concentrations or energy expenditure. There was no relationship between changes in leptin concentrations and changes in energy expenditure, suggesting that leptin is not involved in the stimulation of energy metabolism during overfeeding. Interstitial subcutaneous glucose and lactate concentrations were not altered by CHO OF and FAT OF.
CHO OF, but not FAT OF, increases energy expenditure and leptin concentration.

Full text

Effects of short-term carbohydrate or fat
overfeeding on energy expenditure and plasma
leptin concentrations in healthy female subjects
M Dirlewanger
1
, V di Vetta
1
, E Guenat
1
, P Battilana
1
, G Seematter
1
, P Schneiter
1
,EJe
Âquier
1
and L Tappy
1
*
1
Institute of Physiology, University of Lausanne, 7 rue du Bugnon, 1005 Lausanne Switzerland
OBJECTIVE: To determine the effects of excess carbohydrate or fat intake on plasma leptin concentrations and energy
expenditure.
DESIGN: Ten healthy lean females were studied: (a) during a 3 day isoenergetic diet (ISO); (b) during 3 day
carbohydrate overfeeding (CHO OF); and (c) during 3 day fat overfeeding (FAT OF). During each test, basal metabolic
rate, the energy expended during mild physical activity and recovery, and 24 h energy expenditure (24 h EE) were
measured with indirect calorimetry. The concentrations of glucose and lactate were monitored in subcutaneous
interstitial ¯uid over a 24 h period using microdialysis. Plasma hormone and substrate concentrations were measured
in a blood sample collected in the morning of the fourth day.
RESULTS: CHO OF increased plasma leptin concentrations by 28%, and 24 h EE by 7%. Basal metabolic rate and the
energy expended during physical activity were not affected. FAT OF did not signi®cantly change plasma leptin
concentrations or energy expenditure. There was no relationship between changes in leptin concentrations and
changes in energy expenditure, suggesting that leptin is not involved in the stimulation of energy metabolism during
overfeeding. Interstitial subcutaneous glucose and lactate concentrations were not altered by CHO OF and FAT OF.
CONCLUSIONS: CHO OF, but not FAT OF, increases energy expenditure and leptin concentration.
International Journal of Obesity (2000) 24, 1413±1418
Keywords: leptin; 24 h EE; basal metabolic rate; physical activity; insulin; glucose; microdialysis; overfeeding
Introduction
Maintenance of a constant body weight depends on
the balance between energy intake and energy expen-
diture. Such a balance is known to occur not on a day-
to-day basis but on average over extended periods of
time. Chronic ingestion of energy in excess of energy
expenditure will invariably result in energy storage,
essentially as fat tissue with only a modest stimulation
of energy expenditure.
1
The magnitude of the weight
gain shows considerable interindividual variations,
possibly due in part to genetic factors.
2±4
This obser-
vation of interindividual variations in net energy
deposition during a ®xed energy overload suggests
that overfeeding triggers a variable increase in energy
expenditure. In support of this hypothesis, it has
recently been observed that overfeeding stimulates
24 h energy expenditure (24 h EE), an increase nega-
tively correlated with weight gain.
5
The mechanisms
by which energy expenditure increases during over-
feeding remains unknown.
Overfeeding has been shown to increase leptin gene
expression in adipose tissue and to increase plasma
leptin concentrations.
6
Increased plasma leptin levels
may contribute to limiting weight gain by exerting a
negative feedback on energy intake and by stimulating
energy expenditure.
7±9
This latter effect of leptin
remains, however, poorly documented. In rats, an
increase in energy expenditure in response to exo-
genous leptin administration was observed only after
several days.
10
In contrast with this slow activation of
energy expenditure, leptin administration effectively
prevented the decrease in energy expenditure nor-
mally observed rapidly in food-restricted animals.
11
It also prevented the drop in brown adipose tissue
activity when administered to fasted rats.
12
No data
are available regarding the effects of leptin on energy
expenditure in humans. In non-human primates, how-
ever, leptin administration was shown to activate the
sympathetic nervous system,
13
which may in turn
stimulate energy expenditure.
There is considerable evidence that a high fat
content of the diet is a factor favouring passive over-
consumption and the development of obesity in both
animals and man.
14
It has recently been observed that
plasma leptin concentration decreases in humans
switched from a normal to a high-fat diet.
15
This
decrease in plasma leptin concentration may favour
excessive food intake and lower energy expenditure.
*Correspondence: L Tappy, Institut de physiologie, 7 rue du
Bugnon, 1005 Lausanne, Switzerland.
E-mail: Luc.Tappy@iphysiol.unil.ch
Received 6 October 1999; revised 4 February 2000; accepted
22 May 2000
International Journal of Obesity (2000) 24, 1413±1418
ß2000 Macmillan Publishers Ltd All rights reserved 0307±0565/00 $15.00
www.nature.com/ijo

The metabolic factors which relate energy and macro-
nutrient intake to leptin secretion by adipose tissue
remain incompletely understood. Insulin concentra-
tions may be a major factor linking carbohydrate
intake to leptin secretion.
16 ± 18
One mechanism by
which insulin may increase leptin production is via its
action to increase glucose utilization by adipose
tissue.
19
More speci®cally, stimulation of the oxida-
tive, but not non-oxidative glucose pathway appears to
be associated with leptin production.
19
Catechol-
amines
20
and cortisol
21
have also been shown to
modulate leptin secretion, and changes in the concen-
trations of these hormones during dietary manipula-
tions may participate in the regulation of plasma
leptin concentrations.
In order to further assess the speci®c effects of
nutrients during overfeeding on plasma leptin concen-
tration and on energy expenditure, we studied a group
of healthy lean women during isoenergetic conditions
and during a 3 day period with an excess of 40%
energy above requirements administered either as fat
or as carbohydrate. Energy expenditure was assessed
under each condition, and was related to changes in
plasma leptin concentration. In addition, the concen-
tration of glucose and lactate in subcutaneous adipose
tissue was monitored over 24 h periods by means of
in vivo microdialysis.
Subjects and methods
Subjects
Ten healthy lean women were selected to take part in
this study. Their percentage fat was determined from
skinfold thickness measurements.
22
Their anthropo-
metric characteristics are shown in Table 1. All were
in good physical condition, were not presently taking
any medication, and had no family history of diabetes
mellitus or metabolic disorders. The experimental
protocol was approved by the Ethical Committee
of Lausanne Medical School and all participants
provided informed, written consent.
Dietary conditions
At inclusion, resting energy expenditure was mea-
sured by indirect calorimetry during a 45 ± 60 min
period, using a ventilated hood. Twenty-four-hour
energy requirement was estimated to amount to rest-
ing energy expenditure (in MJ=day) multiplied by 1.3.
The subject was placed on a controlled diet during
three periods of 3 days. On one occasion (isoenergetic
diet, ISO) they received a diet containing 50% of total
energy as carbohydrate, 35% as lipid and 15% as
protein (which consisted mainly of a liquid formula
(Fresubin energy, Fresenius, Stans, CH), supplemen-
ted with orange juice, yoghurt and cream), to be
consumed at speci®ed times. They were instructed
not to consume any other food or drink. Subjects were
carefully instructed to strictly adhere to the dietary
recommendations but no assessment of compliance
could be performed during these 2 days spent as
outpatients. Food was administered under direct con-
trol on the third day which the subjects spent in the
respiratory chamber (see below). On a second occa-
sion, they received an hyperenergetic diet providing
40% excess energy as carbohydrate (carbohydrate
overfeeding: CHO OF). For this purpose, the isoener-
getic diet was supplemented with bread, rice, biscuits
and sugar. On a third occasion, they received the same
40% excess of energy as fat (fat overfeeding: FAT OF
(isocaloric diet supplemented with cheese, potato
chips and chocolate)). The average energy intake
and macronutrient composition corresponding to
these three conditions are shown in Table 2. The
order of administration of each diet was randomized
and each condition was separated by at least a 7
day interval. All studies were performed during the
follicular phase of the menstrual cycle.
Experimental protocol
In the morning of the third day of each dietary
condition, the subjects came to the Institute of Phy-
siology after an overnight fast. A microdialysis cath-
eter (CMA 100, CMA, Stockholm, Sweden) was
inserted into the periumbilical subcutaneous adipose
tissue and was perfused with 0.3 ml=min phosphate-
buffered saline by means of a portable infusion pump
(CMA 106). Thereafter, the subjects moved to a
respiratory chamber and their energy expenditure
was monitored by indirect calorimetry from 8:00 am
to 7:00 am the next day.
23
During this 23 h period,
they received a breakfast at 8:30 am, lunch at 12:00
mid-day and dinner at 6:00 pm, and they exercised on
a treadmill at 4 km=h with a slope of 3% between
10:00 am and 10:30 am. They were required to lay in
bed with the light off between 11:00 pm and 7:00 am
the next day. Dialysate was collected as 1 h fractions
between 8:00 am and 11:00 pm, and as 4 h fractions
between 11:00 pm and 7:00 am the next day. A urine
collection was performed for analysis of urinary
nitrogen excretion. The next day, basal energy expen-
Table 1 Characteristics of the subjects
Age Weight Height Body mass Fat mass
(y) (kg) (m) index (kg=m
2
) (%)
22.4 60.9 2.4 1.67 0.03 21.92.2 27.2 1.4
(20 ± 26) (54 ± 78) (1.52 ± 1.79) (19.3 ± 25.3) (21.5 ± 35.4)
Values are expressed as mean s.d. (range).
Table 2 Diet compositions
Energy intake Carbohydrate Fat Protein
(MJ=day) (%) (%) (%)
ISO 7.5 0.6 50 35 15
CHO OF 10.3 0.4 64 25 11
FAT OF 10.50.5 35 55 11
Energy expenditure and leptin during overfeeding
M Dirlewanger
et al
1414
International Journal of Obesity

diture was measured by indirect calorimetry during
60 min (ventilated hood) with the subject fasted over-
night and lying quietly, and two blood samples were
obtained 10 min apart for determination of basal
hormone and substrate concentrations.
Analytical procedure
Plasma glucose concentrations were measured with a
Beckman glucose analyzer (Beckman Instruments,
Fullerton, CA); plasma beta-hydroxybutyrate concen-
trations were measured enzymatically using a kit from
Boehringer Mannheim, Mannheim, Germany. Plasma
leptin (kit from Linco, St Charles, MO), insulin (kit
from Biochem Immunosystems GmbH, Freiburg, Ger-
many), glucagon (kit from Linco), and cortisol (kit
from DPC, Los Angeles, CA) were determined by
radioimmunoassay. Plasma epinephrine and norepine-
phrine concentrations were determined with HPLC
using electrochemical detection.
24
Calculation
Twenty-four-hours EE and basal energy expenditure
were calculated from
_
VO
2
,
_
VCO
2
and urinary nitrogen
using the equations of Livesey and Elia.
25
Suprabasal
energy expenditure was calculated as (24 h EE) ÿ
(basal energy expenditure).
The effect of exercise on energy expenditure
(energy for physical activities) was assessed by cal-
culating energy expenditure between 10:00 and
11:00 am, ie during the 30 min exercise plus the
30 min recovery period.
Statistical analysis
Plasma hormone and substrate concentrations and
energy expenditure data were compared with
ANOVA and paired t-tests with Bonferroni adjust-
ment. Correlations between changes in plasma leptin
concentration and 24 h EE were assessed using linear
regression analysis.
Results
Compared to an isoenergetic diet, carbohydrate over-
feeding led the next day in the postabsorptive state to
a 28% increase in plasma leptin concentrations, a 24%
decrease in plasma non-esteri®ed fatty acid concen-
trations and a 59% decrease in plasma b-hydroxy-
butyrate concentration, but did not change the plasma
concentrations of major glucoregulatory hormones,
catecholamines and glucose. Fat overfeeding did not
signi®cantly affect any of these parameters (Table 3).
Figure 1 shows the glucose and lactate concentrations
in subcutaneous tissue interstitial ¯uid over 24 h
periods. Both glucose and lactate showed three
major peaks at 9:00 ± 10:00 am, 1:00 pm and
7:00 pm, corresponding to postprandial periods. No
signi®cant difference was observed between the iso-
energetic and the carbohydrate or fat overfeeding
conditions.
Twenty-four-hour EE was increased by 7% after
carbohydrate overfeeding compared to isoenergetic
conditions (P<0.05). Basal energy expenditure and
the energy expended during physical activity were not
affected by carbohydrate overfeeding. Suprabasal 24 h
EE was increased by 31%, but the difference did not
reach statistical signi®cance (P0.07). Fat overfeed-
ing did not signi®cantly affect any component of EE
(Figure 2). There was no correlation between changes
in plasma leptin concentrations and changes in energy
expenditure either expressed as absolute values (car-
bohydrate overfeeding r
2
0.038, fat overfeeding
r
2
0.040), or relative values (r
2
0.074 and 0.051).
Table 3 Basal plasma substrate and hormone concentrations
Isocaloric Carbohydrate Fat
diet overfeeding overfeeding
Glucose (mmol=1) 4.120.07 4.40 0.11 4.30 0.04
Non esteri®ed fatty 0.495 0.031 0.374 0.035* 0.458 0.030
acids (mmol=1)
b-hydroxybutyrate 0.143 0.023 0.077 0.015* 0.148 0.030
(mmol=1)
Insulin (mU=1) 9.8 1.2 10.7 1.4 10.0 1.2
Glucagon (ng=1) 49 3484474
Cortisol (nmol=1) 50978 459 77 51986
Leptin (mg=1) 9.81.7 12.5 1.6* 10.9 1.4
Epinephrine 26 4263263
(pmol=1)
Norepinephrine 20522 207 17 199 13
(pmol=1)
*P<0.05 vs isocaloric diet.
Figure 1 Interstitial glucose and lactate concentrations in sub-
cutaneous adipose tissue in isonergetic conditions (ISO) or
during carbohydrate (CHO OF) or fat (FAT OF) overfeeding.
Energy expenditure and leptin during overfeeding
M Dirlewanger
et al
1415
International Journal of Obesity

There was also no relationship between changes in
leptin concentrations and suprabasal energy expendi-
ture (r
2
0.186 during carbohydrate overfeeding and
0.249 during fat overfeeding).
Discussion
Several observations performed in humans have
demonstrated that leptin secretion and leptin gene
expression in adipocytes are regulated by nutrient
balances. In a study performed in healthy humans, it
was observed that massive overfeeding (120 kcal=kg
body weight) increased plasma leptin concentrations
within a 12 h period; prolonged overfeeding leading to
a 10% weight gain further increased leptin concentra-
tions up to three-fold. This increase was positively
correlated with body fat gain, suggesting that it was
primarily attributable to changes in body composi-
tion.
6
However, short-term fasting led to substantial
reductions of plasma leptin concentrations within
24 h.
26
In both cases, plasma leptin concentrations
rapidly returned to normal levels after the intervention
periods.
The mechanisms responsible for changes in plasma
leptin concentration during over- or underfeeding
remain incompletely elucidated. The drop in plasma
leptin concentration during fasting is concomitant
with the rise in ketone body concentrations, but is
not elicited by infusion of exogenous ketone bodies.
26
The fasting-induced drop in plasma leptin levels
coincides with decreases in both plasma glucose and
insulin concentrations and is prevented by glucose
infusion.
27
However, overfeeding increases both
plasma insulin and glucose concentrations and it is
likely that the high plasma insulin levels stimulate
leptin gene expression and secretion of leptin by the
adipocytes. Insulin-stimulated glucose oxidation in
adipocytes has been shown to regulate leptin secretion
and therefore is also a candidate for stimulating leptin
secretion during carbohydrate overfeeding.
19
In this
study, we measured interstitial glucose and lactate
concentrations in subcutaneous adipose tissue
throughout a 24 h period. Fat or carbohydrate over-
feeding did not alter these two parameters. However,
it has to be kept in mind that interstitial glucose
concentration does not provide information on the
¯ux of glucose into adipocytes, which can be expected
to have been increased during carbohydrate overfeed-
ing. It is therefore likely that the absence of an
increased interstitial lactate concentration during
carbohydrate overfeeding was due to stimulation of
glucose utilization and oxidation in the adipose tissue,
with concomitant reduction of relative non-oxidative
glucose disposal. In a recent study, it was observed
that leptin concentration decreased in women who
switched from a high-carbohydrate to a high-fat iso-
energetic diet, and that this effect may have been
related to decreased plasma glucose and insulin con-
centrations.
15
In the present study we observe that a
short period (3 days) of carbohydrate overfeeding
leads to a moderate 25% increase in plasma leptin
concentration. This effect of carbohydrate overfeeding
occurred without changes in interstitial adipose tissue
concentrations of glucose or lactate. Postabsorptive
plasma insulin, glucagon, cortisol and catecholamine
concentrations, measured the morning after the 3 day
tests, were not signi®cantly altered by the three nutri-
tional conditions. For practical reasons, it was not
possible to obtain blood samples during the experi-
mental days within the respiration chamber. Since
carbohydrate overfeeding is known to stimulate
insulin secretion, it is likely that hyperinsulinaemia
was responsible for the increase in plasma leptin
concentration.
Interestingly, fat overfeeding failed to stimulate
leptin secretion; this condition does not stimulate
insulin secretion, which probably accounts for the
absence of leptin response. These results are consis-
tent with the hypothesis of Havel et al, which suggests
that high-fat feeding leads to an excessive sponta-
neous intake of energy due to a failure to elicit leptin-
mediated suppression of food intake.
15
Carbohydrate, but not fat overfeeding, led to a
modest 7% (about 580 kJ=day) increase in 24 h EE.
Of this 580 kJ=day increase in energy expenditure,
about 150 kJ (5% of the energy content of excess
carbohydrate) can be attributed to the obligatory
thermic effect of the extra amount of carbohydrate
intake. The rest remains unaccounted for. Basal
energy expenditure and the energy expended during
an imposed bout of exercise and its recovery period
were not altered, indicating no change in the energetic
Figure 2 Twenty-four-hour energy expenditure (24 h EE), basal
energy expenditure (BEE), suprabasal energy expenditure
(suprabasal EE), and thermic effect of exercise (TEE) in isoener-
getic conditions (ISO) and during carbohydrate (CHO OF) or fat
(FAT OF) overfeeding. TEE was measured over 1 h, correspond-
ing to 30 min exercise 30 min recovery.
Energy expenditure and leptin during overfeeding
M Dirlewanger
et al
1416
International Journal of Obesity

ef®ciency of exercise. This modest increase in 24 h
EE may be attributed to the stimulation of the facul-
tative components of dietary thermogenesis, or to an
increase in the amount of energy expended in non-
exercise physical activity. A recent report indicates
that 8-weeks of overfeeding increases total energy
expenditure while leaving basal energy expenditure,
the thermic effect of food and the energy cost and
physical activity unchanged.
5
In this study, this
increase in energy expenditure was attributed to
non-exercise physical activity, that is to voluntary
movements not associated with exercise, but occur-
ring throughout the day. It was also observed that this
component of 24 h EE was inversely related to weight
gain. It is therefore possible that carbohydrate over-
feeding stimulates non-exercise physical activity
through mechanisms which remain to be speci®ed.
In contrast with the effects of carbohydrate over-
feeding, fat overfeeding failed to increase signi®cantly
any component of energy expenditure. This may be
partially explained by the fact that the obligatory
energy cost of storing and processing fat is low
compared to carbohydrate.
28
This difference may
also be due to the lack of activation of sympathetic
nervous system activity or to a lower stimulation of
thyroid hormone secretion.
Several observations suggest that leptin administra-
tion increases energy expenditure when administered
in fasted and leptin-de®cient animals,
12,29
as well as
in normal animals
10
(although prolonged periods of
leptin administration are required in the latter case). In
humans, a relationship between plasma leptin concen-
trations and energy expenditure has been observed.
30
Our present observation indicates that carbohydrate
overfeeding increases fasting leptin concentrations,
but not basal energy expenditure. There was also no
correlation between changes in fasting leptin concen-
tration and in 24 h EE. Since we did not measure
plasma leptin concentrations throughout the day, we
cannot exclude a relationship post-prandial leptin
concentration and suprabasal energy expenditure.
However, our results do not support the hypothesis
of a leptin-driven stimulation of energy expenditure
during carbohydrate overfeeding in humans. These
conclusions are consistent with the recent report that a
9-y-old leptin-de®cient girl had normal basal energy
expenditure in regard of her body composition which
did not increase after 12 months of leptin replacement
therapy.
31
We cannot, however, discard the possibility
that the important fat mass loss would have resulted in
a decrease in energy expenditure which was prevented
by leptin treatment. In a recent study,
5
Levine and
collaborators observed that 24 hour energy expendi-
ture was stimulated in healthy lean volunteers sub-
mitted to a period of overfeeding. This stimulation
corresponded essentially to an increase in suprabasal
energy expenditure, while the resting energy expen-
diture, the thermic effect of food and the energetic
ef®ciency of skeletal muscle work were all
unchanged, and was attributed by these authors to
`non-volitional physical activity'. Furthermore, stimu-
lation of this component of energy expenditure
showed considerable interindividual variability and
was inversely correlated with weight gain. Further
studies will be required to assess whether increased
leptin production contributes to stimulate this compo-
nent of energy expenditure during carbohydrate over-
feeding.
In conclusion, our present observations show that
carbohydrate, but not fat overfeeding, leads to modest
increases in both plasma leptin concentrations and
24 h EE but no correlation was found between these
two responses. Stimulation of leptin secretion
occurred without alterations of interstitial glucose
concentrations in adipose tissue. Hyperinsulinaemia
or increased insulin-mediated glucose utilization in
adipose tissue is likely to be involved. Stimulation
of 24 h EE by carbohydrate overfeeding was not
explained by alterations of basal energy expenditure
or the energetic ef®ciency of exercise; it can be
attributed to either stimulation of facultative dietary
thermogenesis or to stimulation of the amount of
energy expended in non-exercise physical activity.
The present data do not support the hypothesis that
stimulation of energy expenditure after carbohydrate
overfeeding is mediated by leptin secretion in humans.
Acknowledgements
This work was supported by a grant from the Swiss
National Science Foundation (no. 32-45387.95, E.
Je
Âquier). The authors thank Fresenius AG (Stans,
Switzerland) for having provided the nutrition
solutions.
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