Ketosis and appetite-mediating nutrients and hormones after weight loss

Abstract

Background/objectives:
Diet-induced weight loss is accompanied by compensatory changes, which increase appetite and encourage weight regain. There is some evidence that ketogenic diets suppress appetite. The objective is to examine the effect of ketosis on a number of circulating factors involved in appetite regulation, following diet-induced weight loss.

Subjects/methods:
Of 50 non-diabetic overweight or obese subjects who began the study, 39 completed an 8-week ketogenic very-low-energy diet (VLED), followed by 2 weeks of reintroduction of foods. Following weight loss, circulating concentrations of glucose, insulin, non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), leptin, gastrointestinal hormones and subjective ratings of appetite were compared when subjects were ketotic, and after refeeding.

Results:
During the ketogenic VLED, subjects lost 13% of initial weight and fasting BHB increased from (mean±s.e.m.) 0.07±0.00 to 0.48±0.07 mmol/l (P<0.001). BHB fell to 0.19±0.03 mmol/l after 2 weeks of refeeding (P<0.001 compared with week 8). When participants were ketotic, the weight loss induced increase in ghrelin was suppressed. Glucose and NEFA were higher, and amylin, leptin and subjective ratings of appetite were lower at week 8 than after refeeding.

Conclusions:
The circulating concentrations of several hormones and nutrients which influence appetite were altered after weight loss induced by a ketogenic diet, compared with after refeeding. The increase in circulating ghrelin and subjective appetite which accompany dietary weight reduction were mitigated when weight-reduced participants were ketotic.

Full text

ORIGINAL ARTICLE
Ketosis and appetite-mediating nutrients and hormones
after weight loss
P Sumithran
1
, LA Prendergast
1,2
, E Delbridge
1
, K Purcell
1
, A Shulkes
3
, A Kriketos
1
and J Proietto
1
BACKGROUND/OBJECTIVES: Diet-induced weight loss is accompanied by compensatory changes, which increase appetite and
encourage weight regain. There is some evidence that ketogenic diets suppress appetite. The objective is to examine the effect
of ketosis on a number of circulating factors involved in appetite regulation, following diet-induced weight loss.
SUBJECTS/METHODS: Of 50 non-diabetic overweight or obese subjects who began the study, 39 completed an 8-week ketogenic
very-low-energy diet (VLED), followed by 2 weeks of reintroduction of foods. Following weight loss, circulating concentrations of
glucose, insulin, non-esterified fatty acids (NEFA), b-hydroxybutyrate (BHB), leptin, gastrointestinal hormones and subjective ratings
of appetite were compared when subjects were ketotic, and after refeeding.
RESULTS: During the ketogenic VLED, subjects lost 13% of initial weight and fasting BHB increased from (mean±s.e.m.) 0.07±0.00
to 0.48±0.07 mmol/l (Po0.001). BHB fell to 0.19±0.03 mmol/l after 2 weeks of refeeding (Po0.001 compared with week 8). When
participants were ketotic, the weight loss induced increase in ghrelin was suppressed. Glucose and NEFA were higher, and amylin,
leptin and subjective ratings of appetite were lower at week 8 than after refeeding.
CONCLUSIONS: The circulating concentrations of several hormones and nutrients which influence appetite were altered after
weight loss induced by a ketogenic diet, compared with after refeeding. The increase in circulating ghrelin and subjective appetite
which accompany dietary weight reduction were mitigated when weight-reduced participants were ketotic.
European Journal of Clinical Nutrition (2013) 67, 759–764; doi:10.1038/ejcn.2013.90; published online 1 May 2013
Keywords: appetite; ketosis; very-low-energy diet; weight loss
INTRODUCTION
The increasing prevalence of overweight and obesity has been
widely reported. Ketogenic low-carbohydrate diets are a popular
means of weight loss, and in the short-term, often result in greater
weight loss than low-fat diets.
1
During fasting or restriction of
dietary carbohydrate intake, fatty acid oxidation in the liver results
in the production of ketones. Although the mechanism of the
efficacy of ketogenic diets has not been definitively established,
it is commonly proposed that ketones suppress appetite,
2,3
and it
has been observed that study participants on ad libitum ketogenic
diets spontaneously restrict their energy intake.
4,5
In the hypothalamus, signals from several circulating
hormones and nutrients are integrated to regulate appetite and
energy expenditure.
6
The peripheral modulators of appetite
include glucose,
7
free-fatty acids
8
and hormones from the
gastrointestinal tract, pancreas and adipose tissue, such as
leptin, insulin, ghrelin, cholecystokinin (CCK), glucagon-like
peptide 1, peptide YY and pancreatic polypeptide.
9–15
Following diet-induced weight loss, a number of compensatory
changes occur, which encourage weight regain and restoration
of energy balance. These include reductions in energy expendi-
ture
16
and circulating leptin,
17
and an increase in the orexigenic
hormone ghrelin.
18
It was recently reported that postprandial
release of CCK, a hormone which increases satiety, was
significantly reduced after diet-induced weight loss.
19
However,
when weight-reduced subjects were ketotic due to restriction of
dietary carbohydrate, CCK release was maintained at preweight
loss concentrations, raising the possibility of an interaction
between circulating ketones and hormonal mediators of appetite.
The aim of the present study was to examine whether a number
of circulating hormones involved in appetite regulation are altered
in the presence of ketosis following diet-induced weight loss.
SUBJECTS AND METHODS
The study was approved by the Austin Health Human Research Ethics
Committee, and all subjects provided written informed consent. A detailed
description of methods has previously been published.
20
In brief,
50 overweight or obese non-diabetic men and postmenopausal women
(mean (±s.d.) age 54.4±10.9 years) undertook a very-low-energy diet
(VLED) for 8 weeks, during which all three daily meals were replaced with a
VLED formulation (Optifast VLCD, Nestle
´Nutrition, Sydney, New South
Wales, Australia) and two cups of low-starch vegetables, according to the
manufacturer’s guidelines, which provided 2.1–2.3 MJ (500–550 kcal) per
day. During the subsequent 2 weeks, subjects who lostX10% of their
starting weight (n¼39) were instructed to gradually substitute the VLED
meal replacements with regular foods, with dietary recommendations
adjusted for individual energy requirements for weight maintenance.
Data collection
Data was collected at baseline (week 0), at week 8 and after the 2 week
transition to regular foods (week 10). After an overnight fast, measures of
anthropometry were taken with subjects wearing light clothing and
barefoot. Bioelectrical impedance was used to measure body weight and
composition (Tanita TBF-300, Tanita, Perth, Western Australia, Australia)
1
Department of Medicine (Austin Health), University of Melbourne, Melbourne, Victoria, Australia;
2
Department of Mathematics and Statistics, La Trobe University, Melbourne,
Victoria, Australia and
3
Department of Surgery (Austin Health), University of Melbourne, Melbourne, Vict oria, Australia. Correspondence: Professor J Proietto, Department of
Medicine, University of Melbourne, Level 2, Boronia Building, Heidelberg Repatriation Hospital, 300 Waterdale Rd, Heidelberg, Victoria 3081, Australia.
E-mail: j.proietto@unimelb.edu.au
Received 1 October 2012; revised 27 March 2013; accepted 3 April 2013; published online 1 May 2013
European Journal of Clinical Nutrition (2013) 67, 759– 764
&
2013 Macmillan Publishers Limited All rights reserved 0954-3007/13
www.nature.com/ejcn

using the standard adult mode of measurement. A baseline blood sample
was collected, and subjects were asked to rate their appetite using a
validated visual analogue scale.
21
A standardized breakfast was provided,
which consisted of a boiled egg, toast, margarine, orange juice, cereal
biscuits (Weet-Bix; Sanitarium, Berkeley Vale, New South Wales, Australia)
and whole milk. This meal contained 2.3 MJ (550 kcal), of which B51%
energy was from carbohydrate, 33% from fat and 16% from protein. Blood
samples and VAS ratings of appetite were collected 30, 60, 120, 180 and
240 min thereafter.
Biochemical assays
Blood was collected into prepared tubes, spun in a refrigerated centrifuge,
and frozen for later analysis. Plasma for b-hydroxybutyrate (BHB), non-
esterified fatty acids (NEFA) and CCK were stored at 801C. All other
aliquots were stored at 20 1C. Fasting and postprandial plasma acylated
ghrelin, active glucagon-like peptide 1, total glucose-dependent insulino-
tropic polypeptide (GIP), pancreatic polypeptide, amylin and peptide YY
concentrations were measured using the human gut hormone panel
Lincoplex kit (Millipore, Sydney, New South Wales, Australia), a multiplex
assay kit, which uses antibody-immobilised beads to simultaneously
quantify peptide hormones. The sensitivity of the assay is 1.8, 5.2, 0.2, 2.4,
3.2 and 8.4 pg/ml respectively, for the hormones as listed above.
Intra-assay and inter-assay variation are o11% and o19% respectively.
Plasma insulin and leptin were measured by commercial radioimmuno-
assay (Millipore). CCK was measured in ethanol-extracted plasma
using antiserum 92128 (generous donation of Prof Jens Rehfeld,
University Hospital, Copenhagen, Denmark) and
125
I-Bolton-Hunter-CCK8
label (Perkin Elmer, Melbourne, Victoria, Australia). The antiserum is specific
for CCK-amide with negligible cross-reactivity to gastrin-amide or gly-
extended forms of gastrin and CCK. NEFA was measured by enzymatic
colorimetry (Wako, Osaka, Japan). Glucose was measured by the glucose
oxidase method (GM7 Analox glucose analyzer, Helena Laboratories,
Melbourne, Victoria, Australia). BHB was measured using a colorimetric
assay (Unicel DxC 800 Synchron Clinical System analyzer, Beckman Coulter,
Sydney, New South Wales, Australia). Circulating levels of other ketones
(acetoacetate and acetone) were not measured, as the increase in ketones
during food restriction is predominantly due to BHB.
22
Statistical analysis
Analyses included the 39 of 50 subjects who completed all three data
collection visits. At baseline, data were missing from one subject for the
gut hormone multiplex, two subjects for CCK and three subjects for NEFA,
due to difficulty obtaining sufficient blood for analysis. Of the remaining
data, o2% was missing at random, and was replaced using linear
interpolation. Analyses were carried out using R version 2.13.1.
23
Repeated
measures ANOVA to compare measurements between study visits was
done by fitting a generalized least squares model with an unstructured
error covariance. Comparison between weeks was carried out using Wald
tests applied to the generalized least squares-fitted model. For data which
was not normally distributed, the log or square-root transformation was
used, although means and s.e.m. are reported on the original scale.
The pairwise comparisons between weeks in Tables 1 and 2 were also
adjusted by the Benjamini and Yekutieli method
24
to account for multiple
comparisons, and P-values which no longer remain significant after
adjustment are indicated on the tables. A table of changes in
anthropometry, fasting and 4-h area under curve (AUC) of nutrients,
hormones and VAS scores between weeks 0– 8, 0–10 and 8–10 showing
P-values for comparisons between weeks before and after adjustment for
multiple comparisons is provided in the Supplementary Data section.
Correlations reported are Spearman rank correlations (r), and 95%
confidence intervals (CI) were calculated using the bootstrap approach.
Insulin resistance was estimated by the homoeostasis model of assessment
of insulin resistance, using the formula homoeostasis model of assessment
of insulin resistance (HOMA-IR) ¼(fasting glucose (mmol/l) fasting
insulin (mU/l))/22.5.
25
Values are given as means±s.e.m. unless otherwise
specified.
RESULTS
Effect of diet on anthropometric measurements
Measures of anthropometry and blood pressure at baseline, and
changes following 8 weeks of VLED and after 2 weeks of
reintroduction of food are shown in Table 1.
Eight weeks on a VLED resulted in a mean loss of 13% initial
body weight, with significant reductions in adiposity, waist and
hip circumferences and blood pressure. There were minor, but
statistically significant, changes in anthropometric parameters
between weeks 8 and 10.
Ketosis
Fasting BHB increased from 0.07±0.00 to 0.48±0.07 mmol/l
after 8 weeks of VLED (Po0.001), and fell to 0.19±0.03 mmol/l
after 2 weeks of food reintroduction (Po0.001, compared with
weeks 0 and 8).
Nutrients and hormones during ketosis (week 8) and after
refeeding (week 10) in weight-reduced participants
Mean fasting and 4-h postprandial values for glucose, NEFA,
ghrelin and amylin at weeks 0, 8 and 10 are depicted in Figure 1.
Mean fasting and 4-h AUC values at baseline, and changes from
baseline at weeks 8 and 10 for nutrients and hormones are shown
in Table 2.
Glucose, insulin. Weight loss led to significant reductions in
fasting glucose and insulin, resulting in a significant improvement
in insulin resistance, estimated by homoeostasis model of
assessment of insulin resistance, from week 0 to 8. There were
no significant changes in these measurements between weeks 8
and 10.
Four-h postprandial AUC for insulin fell significantly with weight
loss, and was not significantly different between weeks 8 and 10.
In contrast, AUC glucose did not change significantly with VLED-
induced weight loss, but fell after refeeding (Table 2). There were
significant correlations between BHB and AUC glucose at week 8
Table 1. Anthropometric and blood pressure measurements at baseline (mean s.d.), and changes after weight loss (mean±s.e.m.) when subjects
were ketotic (week 8) and after refeeding (non-ketotic, week 10)
Measure Week 0 DWeek 0–8
(ketotic)
DWeek 0–10
(non-ketotic)
DWeek 8–10 P-value
(week 8 versus 10)
Weight (kg) 96.2 (13.6) 12.5±0.5
z
13.0±0.5
z
0.5±0.1 o0.001
BMI (kg/m
2
) 34.7 (3.5) 4.5±0.1
z
4.7±0.1
z
0.2±0.1 o0.001
Waist circumferance (cm) 103.3 (10.6) 9.9±0.5
z
10.6±0.5
z
0.7±0.4 0.07
Hip circumferance (cm) 120.3 (8.0) 8.1±0.4
z
8.9 ±0.4
z
0.8±0.3 0.002
Fat mass (kg) 49.5 (11.2) 13.4±0.7
z
14.6±0.8
z
1.2±0.3 o0.001
Systolic BP (mmHg) 136.0 (19.8) 17.6±2.4
z
13.9±2.4
z
3.7±1.7 0.03
a
Diastolic BP (mmHg) 82.7 (11.1) 9.2 ±1.9
z
10.0±1.6
z
0.8±1.8 0.68
Symbols denote significant differences from week 0 (
z
Pp0.001). Repeated measures ANOVA reported highly significant changes over weeks for all measures
(all P-valueo0.001).
a
Indicates pairwise comparisons, which did not remain significant after adjustment for multiple comparisons.
Ketosis and appetite after weight loss
P Sumithran et al
760
European Journal of Clinical Nutrition (2013) 759 – 764 &2013 Macmillan Publishers Limited

(P¼0.40; 95% CI (0.06, 0.67)), and between changes in BHB and
AUC glucose from week 8 to 10 (P¼0.49; 95% CI (0.20, 0.71)).
NEFA. Four-h postprandial AUC for NEFA was elevated at week 8,
but after 2 weeks of refeeding was not significantly different
from baseline values (Table 2). There were significant correlations
between BHB and AUC NEFA at week 8 (P¼0.49; 95% CI
(0.18, 0.69)), and between changes in BHB and AUC NEFA from
week 8 to 10 (P¼0.43; 95% CI (0.11, 0.69)).
Leptin. Fasting leptin fell significantly with weight loss, and
increased slightly following reintroduction of food, even when
adjusted for fat mass. There were inverse correlations between
leptin and BHB at week 8 (P¼0.44; 95% CI ( 0.68, 0.09)),
and between changes in leptin and BHB from weeks 8 to 10
(P¼0.33; 95% CI ( 0.61, 0.01)).
Gastrointestinal peptides. At week 8, weight-reduced subjects
had significantly lower fasting ghrelin, peptide YY, amylin and
pancreatic polypeptide, compared with week 10 values.
Fasting GIP, glucagon-like peptide 1 and CCK were not different
in weight-reduced subjects between weeks 8 and 10 (Table 2).
Four-h AUC values for ghrelin and amylin were significantly
lower at week 8 than at week 10 (Po0.001 for both, Figure 1).
AUC ghrelin increased significantly between weeks 0 and 8 in
participants who did not achieve ketosis (BHB 40.3 mmol/l) at
week 8, but the weight loss induced increase in ghrelin was
completely suppressed in subjects who were ketotic. There were
significant inverse correlations between BHB and AUC ghrelin at
Table 2. Fasting and 4-h AUC of nutrient, hormone and VAS values at week 0 (mean s.d.), and changes from baseline at weeks 8 and 10
(mean±s.e.m.)
Measure Week 0 DWeek 0–8
(ketotic)
DWeek 0–10
(non-ketotic)
DWeek 8–10 P-value
(week 8 versus 10)
Fasting
Glucose
a
5.8 (0.9) 0.6±0.1
z
0.4±0.1w0.2±0.1 0.07
Insulin
a
18.1 (9.8) 9.0±1.2
z
8.3±1.2
z
0.7±0.5 0.17
HOMA-IR
a
4.7 (2.8) 2.6±0.4
z
2.4±0.4
z
0.3±0.1 0.08
BHB 0.07 (0.0) 0.43±0.08
z
0.12±0.03
z
0.3±0.06 o0.001
NEFA
a
0.5 (0.3) 0.3±0.1
z
0.1±0.05 0.2±0.05 o0.001
Leptin
a
33.2 (18.3) 23.4±2.2
z
21.1±2.2
z
2.3±0.6 o0.001
Leptin/fat mass
a
0.66 (0.3) 0.41±0.04
z
0.34±0.04
z
0.07±0.02 o0.001
Ghrelin
a
122.0 (89.2) 4.4±9.1 52.8±9.0
z
49.2±9.5 o0.001
PYY
a
68.3 (33.0) 19.7±4.4
w
13.6±4.2 6.4±3.2 0.02
b
GIP 18.3 (10.5) 4.1±2.3 1.3±2.5 2.8±1.8 0.12
GLP-1
a
40.2 (17.2) 6.2±2.1
w
5.3±2.5
w,b
0.1±2.1 0.88
PP
a
66.4 (67.5) 19.2±10.2 5.7 ±10.5 24.9±8.0 o0.001
Amylin
a
83.1 (52.1) 50.5±7.9
z
34.8±8.2
z
15.5±2.9 o0.001
CCK
a
1.7 (1.0) 0.6±0.2
z
0.5±0.2
z
0.1±0.1 0.19
4-h AUC
Glucose 1487 (262) 25.8±42 66±32*
,b
90.6±30 0.003
Insulin
a
12 086 (7728) 4722±974
z
4574±899
z
147±422 0.36
NEFA
a
71.9 (29.1) 40.1±6.8
z
9.4±4.4 30.7±5.5 o0.001
Ghrelin
a
23 034 (16703) 1136±2023 9696±1937
z
8877±1743 o0.001
PYY
a
18 190 (6384) 2580±665
z
1771±571w754±602 0.21
GIP
a
18 384 (8471) 9011±2004
z
6755±2057w2537±1220 0.06
GLP-1 11 471 (4087) 460±608 353±560 130±431 0.97
PP 40 991 (23757) 7358±3404 9384±3775*
,b
834±3160 0.68
Amylin
a
35 900 (3340) 16 880±3049
z
11 875±3170
z
5027±1113
z
o0.001
CCK 730 (317) 64±44 100±47w
b
29±31 0.36
Fasting
Hunger
a
31.9 (26.3) 2.6±4.7 9.6±4.8*
b
7.0±3.8 0.03
b
Full 44.2 (25.9) 0.5±4.3 7.2±4.1 7.2±3.6 0.05
Desire 40.8 (25.1) 0.9±4.5 4.6±4.5 5.4±3.2 0.09
Prospective
a
42.8 (18.8) 0.2±3.1 6.0±2.9*
,b
6.2±2.6 0.02
b
Urge
a
32.7 (23.3) 2.5±3.8 11.1±4.2*
,b
8.5±3.1 0.006
b
Preoccupied 36.2 (23.3) 4.9±4.0 5.0±4.0 0.0±3.0 1.00
4-h AUC
Hunger 5181 (2538) 847±499 1463±542*
,b
616±397 0.10
Full 12 806 (5326) 491±848 783±853 292±534 0.59
Desire
a
5694 (2902) 796±542 1456±562*
,b
660±334 0.05
Prospective 7125 (2883) 715±525 992±534 277±257 0.40
Urge 5457 (2922) 831±455 1473±533*
,b
642±346 0.07
Preoccupied 5144 (3279) 597±524 880±537 283±293 0.42
Abbreviations: AUC, area under curve; BHB, b-hydroxybutyrate; CCK, cholecystokinin; GLP-1, glucagon-like peptide 1; GIP, glucose-dependent insulinotropic
polypeptide; HOMA-IR, homeostasis model of assessment of insulin resistance; NEFA, non-esterified fatty acids; PP, pancreatic polypeptide; PY Y, peptide YY.
Units are as follows: insulin mU/l; HOMA-IR units; leptin ng/ml; PYY, GIP, GLP-1, PP pg/ml; CCK fmol/ml, VAS millimetres (mm), with possible range 0–100 mm
for fasting values. Repeated measures ANOVA reported significant changes over weeks for measures denoted by
a
Symbols denote significant differences from
week 0 (
z
Pp0.001,
w
Pp0.01, * Po0.05).
b
Indicates pairwise comparisons, which did not remain significant after adjustment for multiple comparisons.
Ketosis and appetite after weight loss
P Sumithran et al
761
&2013 Macmillan Publishers Limited European Journal of Clinical Nutrition (2013) 759 – 764

week 8 (P¼0.34; 95% CI ( 0.62, 0.04)), and between
changes in BHB and AUCs for ghrelin (P¼0.48, 95% CI ( 0.70,
0.22)) and amylin (P¼0.43, 95% CI ( 0.68, 0.12)) from
week 8 to 10. AUC GIP tended to be higher at week 8 compared
with week 10. AUC CCK was not significantly different from
baseline at week 8, but was significantly lower than baseline
values at week 10. At week 8, there was a significant correlation
between BHB and AUC CCK (P¼0.38; 95% CI (0.11, 0.61)).
AUCs for peptide YY, glucagon-like peptide 1 and pancreatic
polypeptide were not significantly different between weeks
8 and 10.
Appetite during ketosis and after refeeding in weight-reduced
participants
Appetite ratings at week 0, and changes from baseline at
weeks 8 and 10 are presented in Table 2.
At week 8, fasting and AUC ratings of appetite were unchanged
compared with baseline. However, after 2 weeks of refeeding
(week 10), fasting scores for hunger, urge to eat and prospective
consumption rose significantly, and fullness tended to decrease.
At week 10, AUCs for hunger, urge and desire to eat were
significantly higher than preweight loss levels (P¼0.02, 0.02 and
0.04 respectively; all P40.05 after adjustment for multiple
comparisons).
DISCUSSION
Although an inhibitory effect of ketosis on appetite is widely
assumed, there is little information regarding the effect of
ketosis on circulating factors involved in mediating hunger
and satiety.
It is well-established that diet-induced weight loss is accom-
panied by changes in energy expenditure and concentrations of
appetite-regulating hormones, in a manner which encourages
weight regain and restoration of energy balance.
16–20,26
It has
been shown that postprandial release of CCK is maintained at the
preweight loss level following an 8-week ketogenic VLED, but
reduced when weight-reduced subjects are no longer ketotic.
19
The present study confirms this finding, and uncovers several
other factors, which are altered in ketotic weight-reduced
subjects. Subjective ratings of appetite were significantly lower
when weight-reduced subjects were ketotic than following
refeeding.
In mildly ketotic participants, the increase in the circulating
concentration of ghrelin, a potent stimulator of appetite, which
otherwise occurs as a result of diet-induced weight loss, was
suppressed. The present findings are in keeping with a recent
report of a 12-week carbohydrate-restricted diet, during which 28
overweight subjects lost B6.5% of their starting weight without a
significant change in fasting plasma ghrelin.
27
In our study,
postprandial ghrelin concentrations were also measured, and
found to remain unchanged following weight loss as long as
subjects were ketotic. After refeeding, fasting and postprandial
ghrelin concentrations rose significantly.
Our findings of elevated NEFA after 8 weeks on a
low-carbohydrate VLED with return to baseline values after
carbohydrate reintroduction are not surprising, as carbohydrate
restriction stimulates adipocyte lipolysis and ketogenesis. In
rodents, intracerebroventricular administration of a long-chain
fatty acid markedly reduced food intake and hypothalamic
expression of neuropeptide Y, a potent stimulator of appetite,
8
and peripheral infusion of lipids has been shown to reduce
voluntary food intake in humans.
28
It has been hypothesized that
fatty acids may provide a signal to the hypothalamus of nutrient
abundance,
8
and this may contribute to the appetite-reducing
effects of ketogenic low-carbohydrate diets.
The observation that ketosis did not affect fasting glucose,
but was associated with elevated postprandial blood glucose
concentrations is interesting. As postprandial reductions in blood
glucose may increase hunger,
7
(the ‘glucostatic theory’ of
food intake regulation, first proposed by Mayer more than
60 years ago
29
), the effect of ketosis on postprandial glucose
may contribute to appetite reduction. Reports of ketogenic low-
carbohydrate diets having beneficial effects on insulin sensitivity
in humans
30,31
have used the homoeostasis model assessment of
insulin resistance or quantitative insulin sensitivity check index
(QUICKI), which take into account only fasting glucose and insulin
measurements. Conversely, using hyperinsulinemic euglycemic
clamps, it was demonstrated that a ketogenic diet reduces the
ability of insulin to suppress endogenous glucose production, and
impairs insulin-stimulated glucose oxidation.
32
Elevated NEFA may
also contribute to insulin resistance.
33
In rats, intracerebroventricular infusion of BHB reduces food
intake and body weight,
34
and there is recent in vitro evidence
5.0
0
Time (mins)
Glucose (mmol/L)
Week 0
0.2
0
Time (mins)
NEFA (mEq/L)
0
0
Time
Ghrelin (pg/ml)
0
0
Time
Amylin (pg/ml)
7.5
7.0
6.5
6.0
5.5
200
150
100
50
30 60 120 180 240
30 60 120 180 240
0.4
0.6
0.8
30 60 120 180 240
200
150
100
50
30 60 120 180 240
Week 8 Week 10
*
Week 0 Week 8 Week 10
‡
Week 0 Week 8
‡
Week 10
‡
Week 0 Week 8
‡
Week 10
Figure 1. Mean fasting and postprandial glucose (a), NEFA (b), ghrelin (c) and amylin (d) at weeks 0, 8 and 10. Symbols indicate significant
differences in AUCs compared with week 0 (*Po0.05;
z
Pp0.001).
Ketosis and appetite after weight loss
P Sumithran et al
762
European Journal of Clinical Nutrition (2013) 759 – 764 &2013 Macmillan Publishers Limited

that BHB may directly reduce central orexigenic signalling.
35
Peripheral injection of BHB also reduces food intake, and this
effect is eliminated by transection of the common hepatic branch
of the vagus nerve.
36
Of note, this branch primarily contains
afferent fibres originating in the proximal small intestine, stomach
and pancreas, which have been shown to be sensitive to
stimulation by CCK.
37
Ghrelin also conveys its orexigenic signal
to the brain via the vagus nerve.
38
The preservation of preweight-
loss profiles of ghrelin and CCK release may thereby contribute to
the suppressive effect of ketosis on appetite.
It is interesting to note that not all hormones changed in a
direction which would contribute to appetite suppression by
ketosis. Leptin was lower after 8 weeks on a VLED than following 2
weeks of refeeding, even when adjusted for fat mass. This is
consistent with previous reports of a lower plasma leptin during
dynamic weight loss than after maintenance of the reduced
weight,
39
and is in keeping with the hypothesis that the role of
leptin is more as an emergency signal of energy depletion than
an inhibitor of food intake.
39
Amylin is cosecreted with insulin
by pancreatic b-cells, and reduces food intake directly in the area
postrema,
40
and also via mediation of the anorexic effects of other
hormones including CCK.
41
GIP, an incretin hormone, appears to
promote energy storage.
42
The weight loss induced reduction
in amylin and increase in GIP, which would be expected to
encourage regain of lost body weight, were somewhat attenuated
following refeeding. It is difficult to explain the seemingly
contradictory effects of ketosis on different hormones and
nutrients involved in appetite regulation. Nonetheless, subjective
ratings of appetite were lower when participants were ketotic. It is
possible that central sensitivity to the anorexic effect of hormones
such as leptin and amylin may be altered by ketosis, or that
interaction between various hormones is affected. The relative
potency of the multitude of factors involved in appetite regulation
is also unknown, and it may be that the increase in hunger
following the reduction in ketosis reflects the strength of ghrelin
as an orexigenic signal.
It should be noted that although the majority of randomized
controlled trials comparing ad libitum ketogenic low-carbohydrate
diets with low-fat diets have found greater weight loss over
6 months on the ketogenic diets, the difference is no longer
observed at 12 months.
1
In one of these studies, urinary ketones
were significantly higher in the low-carbohydrate group compared
with the low-fat group over the first 12 weeks, but no relationship
was found between urinary ketones and weight loss.
43
Only a
minority of people have detectable urinary ketones after
3–6 months on low-carbohydrate diets.
5,43
This study has limitations. Subjects were undergoing active
weight loss after 8 weeks on the VLED, compared with relative
weight stability after 2 weeks of food reintroduction, which could
have influenced the concentration of measured hormones and
nutrients. However, compensatory mechanisms aimed at restoring
energy balance would be expected to be more pronounced
during dynamic weight loss, so this is likely to minimize the
predominantly anorexigenic changes detected while subjects
were ketotic. There was a small but statistically significant
reduction in body weight and adiposity between weeks 8 and
10. This difference, representing a reduction in initial weight of
13.6% (week 10) compared with 13.1% (week 8), is unlikely to be
of sufficient magnitude to affect the hormone and appetite
results. It has previously been shown that circulating ghrelin
increases significantly following a diet-induced loss of 8.5% of
initial body weight.
44
Perhaps due to fear of weight regain, it is
likely that not all participants consumed the prescribed amount of
carbohydrates during the period of food reintroduction, and
although BHB concentrations decreased significantly between
week 8 and 10, they did not return to baseline values by week 10.
This is likely to underestimate the effect of ketosis on the appetite-
regulating hormones and nutrients measured. Although we have
demonstrated associations between ketones and appetite-
regulating hormones, this does not indicate causality. However,
it has been shown in mice that infusion of BHB increases
circulating CCK and reduces food intake.
45
A similar study
with measurement of other appetite-regulating hormones would
be informative.
In conclusion, following diet-induced weight loss, the circulat-
ing concentrations of several hormones and nutrients which
influence appetite were altered when participants were ketotic,
compared with after refeeding. The increases in circulating ghrelin
and subjective appetite which accompany dietary weight reduc-
tion were mitigated when weight-reduced participants were
ketotic. Further research is needed to determine the precise
mechanism of this effect.
CONFLICT OF INTEREST
JP was chairman of the Optifast medical advisory board at the time the study was
conducted. The other authors have no conflict of interest.
ACKNOWLEDGEMENTS
This work was supported by NHMRC project grant (508920), Endocrine Society of
Australia scholarship (PS), Royal Australasian College of Physicians Shields Research
Entry scholarship (PS), and Sir Edward Dunlop Medical Research Foundation (JP). We
thank Celestine Bouniu, John Cardinal, Sherrell Cardinal, Christian Rantzau, Rebecca
Sgambellone, Sherley Visinoni and Mildred Yim for technical assistance.
REFERENCES
1 Nordmann AJ, Nordmann A, Briel M, Keller U, Yancy Jr. WS, Brehm BJ et al.
Effects of low-carbohydrate vs low-fat diets on weight loss and cardiovascular risk
factors: a meta-analysis of randomized controlled trials. Arch Intern Med 2006; 166:
285–293.
2 Astrup A, Meinert Larsen T, Harper A. Atkins and other low-carbohydrate diets:
hoax or an effective tool for weight loss? Lancet 2004; 364: 897–899.
3 Erlanson-Albertsson C, Mei J. The effect of low carbohydrate on energy meta-
bolism. Int J Obes (Lond) 2005; 29(Suppl 2): S26–S30.
4 Boden G, Sargrad K, Homko C, Mozzoli M, Stein TP. Effect of a low-carbohydrate
diet on appetite, blood glucose levels, and insulin resistance in obese patients
with type 2 diabetes. Ann Intern Med 2005; 142: 403–411.
5 Yancy Jr. WS, Olsen MK, Guyton JR, Bakst RP, Westman EC. A low-carbohydrate ,
ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia: a
randomized, controlled trial. Ann Intern Med 2004; 140: 769–777.
6 Schwartz MW, Woods SC, Porte Jr. D, Seeley RJ, Baskin DG. Central nervous system
control of food intake. Nature 2000; 404: 661–671.
7 Campfield LA, Smith FJ, Rosenbaum M, Hirsch J. Human eating: evidence for a
physiological basis using a modified paradigm. Neurosci Biobehav Rev 1996; 20:
133–137.
8 Obici S, Feng Z, Morgan K, Stein D, Karkanias G, Rossetti L. Central administration
of oleic acid inhibits glucose production and food intake. Diabetes 2002; 51:
271–275.
9 Batterham RL, Cowley MA, Small CJ, Herzog H, Cohen MA, Dakin CL et al. Gut
hormone PYY[sub3-36] physiologically inhibits food intake. Nature 2002; 418:
650–654.
10 Batterham RL, Le Roux CW, Cohen MA, Park AJ, Ellis SM, Patterson M et al.
Pancreatic polypeptide reduces appetite and food intake in humans.
J Clin Endocrinol Metab 2003; 88: 3989–3992.
11 Gutzwiller JP, Goke B, Drewe J, Hildebrand P, Ketterer S, Handschin D et al.
Glucagon-like peptide-1: a potent regulator of food intake in humans. Gut 1999;
44: 81–86.
12 Moran TH, Kinzig KP. Gastrointestinal satiety signals II. Cholecystokinin.
Am J Physiol Gastrointest Liver Physiol 2004; 286: G183–G188.
13 Rezek M. The role of insulin in the glucostatic control of food intake. Can J Physiol
Pharmacol 1976; 54: 650–665.
14 Wren AM, Seal LJ, Cohen MA, Brynes AE, Frost GS, Murphy KG et al. Ghrelin
enhances appetite and increases food intake in humans. J Clin Endocrinol Metab
2001; 86: 5992–5995.
15 Zhang Y, Proenca R, Maffei M, Barone M, Leopold L, Friedman JM. Positional
cloning of the mouse obese gene and its human homologue. Nature 1994; 372:
425–432.
16 Leibel RL, Hirsch J. Diminished energy requirements in reduced-obese patients.
Metabolism 1984; 33: 164–170.
Ketosis and appetite after weight loss
P Sumithran et al
763
&2013 Macmillan Publishers Limited European Journal of Clinical Nutrition (2013) 759 – 764

17 Geldszus R, Mayr B, Horn R, Geisthovel F, von zur Muhlen A, Brabant G.
Serum leptin and weight reduction in female obesity. Eur J Endocrinol 1996; 135:
659–662.
18 Cummings DE, Weigle DS, Frayo RS, Breen PA, Ma MK, Dellinger EP et al. Plasma
ghrelin levels after diet-induced weight loss or gastric bypass surgery.
N Engl J Med 2002; 346: 1623–1630.
19 Chearskul S, Delbridge E, Shulkes A, Proietto J, Kriketos A. Effect of weight loss
and ketosis on postprandial cholecystokinin and free fatty acid concentrations.
Am J Clin Nutr 2008; 87: 1238–1246.
20 Sumithran P, Prendergast LA, Delbridge E, Purcell K, Shulkes A, Kriketos A et al.
Long-term persistence of hormonal adaptations to weight loss. New Engl J Med
2011; 365: 1597–1604.
21 Stubbs RJ, Hughes DA, Johnstone AM, Rowley E, Reid C, Elia M et al. The
use of visual analogue scales to assess motivation to eat in human subjects: a
review of their reliability and validity with an evaluation of new hand-held
computerized systems for temporal tracking of appetite ratings. Br J Nutr 2000;
84: 405–415.
22 Hall SE, Wastney ME, Bolton TM, Braaten JT, Berman M. Ketone body kinetics in
humans: the effects of insulin-dependent diabetes, obesity and starvation. J Lipid
Res 1984; 25: 1184–1194.
23 R Development Core Team. R: A Language and Environment for Statistical
Computing. R Foundation for Statistical Computing: Vienna, 2011.
24 Benjamini Y, Yekutieli D. The control of the false discovery rate in multiple testing
under dependency. Ann Statist 2001; 29: 1165–1188.
25 Matthews DR, Hosker JP, Rudenski AS, Naylor BA, Treacher DF, Turner RC.
Homoeostasis model assessment: insulin resistance and beta-cell function from
fasting plasma glucose and insulin concentrations in man. Diabetologia 1985; 28:
412–419.
26 Pfluger PT, Kampe J, Castaneda TR, Vahl T, D’Alessio DA, Kruthaupt T et al. Effect of
human body weight changes on circulating levels of peptide YY and peptide
YY3-36. J Clin Endocrinol Metab 2007; 92: 583–588.
27 Ratliff J, Mutungi G, Puglisi MJ, Volek JS, Fernandez ML. Carbohydrate restriction
(with or without additional dietary cholesterol provided by eggs) reduces insulin
resistance and plasma leptin without modifying appetite hormones in adult men.
Nutr Res 2009; 29: 262–268.
28 Gil KM, Skeie B, Kvetan V, Askanazi J, Friedman MI. Parenteral nutrition and
oral intake: effect of glucose and fat infusions. J Parenter Enteral Nutr 1991; 15:
426–432.
29 Mayer J. Glucostatic mechanism of regulation of food intake. N Engl J Med 1953;
249: 13–16.
30 Samaha FF, Iqbal N, Seshadri P, Chicano KL, Daily DA, McGrory J et al. A low-
carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med
2003; 348: 2074–2081.
31 Volek JS, Sharman MJ, Gomez AL, DiPasquale C, Roti M, Pumerantz A et al.
Comparison of a very low-carbohydrate and low-fat diet on fasting lipids, LDL
subclasses, insulin resistance, and postprandial lipemic responses in overweight
women. J Am Coll Nutr 2004; 23: 177–184.
32 Bisschop PH, de Metz J, Ackermans MT, Endert E, Pijl H, Kuipers F et al. Dietary fat
content alters insulin-mediated glucose metabolism in healthy men. Am J Clin
Nutr 2001; 73: 554–559.
33 Liu J, Jahn LA, Fowler DE, Barrett EJ, Cao W, Liu Z. Free fatty acids induce insulin
resistance in both cardiac and skeletal muscle microvasculature in humans. J Clin
Endocrinol Metab 2011; 96: 438–446.
34 Arase K, Fisler JS, Shargill NS, York DA, Bray GA. Intracerebroventricular infusions
of 3-OHB and insulin in a rat model of dietary obesity. Am J Physiol 1988; 255:
R974–R981.
35 Laeger T, Pohland R, Metges CC, Kuhla B. The ketone body beta-hydroxybutyric
acid influences agouti-related peptide expression via AMP-activated protein
kinase in hypothalamic GT1-7 cells. J Endocrinol 2012; 213: 193–203.
36 Langhans W, Egli G, Scharrer E. Selective hepatic vagotomy eliminates
the hypophagic effect of different metabolites. J Auton Nerv Syst 1985; 13:
255–262.
37 Horn CC, Friedman MI. Separation of hepatic and gastrointestinal signals from the
common ‘hepatic’ branch of the vagus. Am J Physiol Regul Integr Comp Physiol
2004; 287: R120–R126.
38 Date Y, Murakami N, Toshinai K, Matsukura S, Niijima A, Matsuo H et al.
The role of the gastric afferent vagal nerve in ghrelin-induced feeding
and growth hormone secretion in rats. Gastroenterology 2002; 123:
1120–1128.
39 Rosenbaum M, Nicolson M, Hirsch J, Murphy E, Chu F, Leibel RL. Effects of weight
change on plasma leptin concentrations and energy expenditure. J Clin Endocrinol
Metab 1997; 82: 3647–3654.
40 Riediger T, Schmid HA, Lutz T, Simon E. Amylin potently activates AP neurons
possibly via formation of the excitatory second messenger cGMP. Am J Physiol
Regul Integr Comp Physiol 2001; 281: R1833–R1843.
41 Lutz TA, Tschudy S, Rushing PA, Scharrer E. Attenuation of the anorectic effects of
cholecystokinin and bombesin by the specific amylin antagonist AC 253. Physiol
Behav 2000; 70: 533–536.
42 Hauner H, Glatting G, Kaminska D, Pfeiffer EF. Effects of gastric inhibitory poly-
peptide on glucose and lipid metabolism of isolated rat adipocytes. Ann Nutr
Metab 1988; 32: 282–288.
43 Foster GD, Wyatt HR, Hill JO, McGuckin BG, Brill C, Mohammed BS et al. A ran-
domized trial of a low-carbohydrate diet for obesity. N Engl J Med 2003; 348:
2082–2090.
44 Garcia JM, Iyer D, Poston WSC, Marcelli M, Reeves R, Foreyt J et al. Rise of plasma
ghrelin with weight loss is not sustained during weight maintenance. Obesity
(Silver Spring) 2006; 14: 1716–1723.
45 Visinoni S, Khalid NFI, Joannides CN, Shulkes A, Yim M, Whitehead J et al. The role
of liver fructose-1,6-bisphosphatase in regulating appetite and adiposity. Diabetes
2012; 61: 1122–1132.
Supplementary Information accompanies this paper on European Journal of Clinical Nutrition website (http://www.nature.com/ejcn)
Ketosis and appetite after weight loss
P Sumithran et al
764
European Journal of Clinical Nutrition (2013) 759 – 764 &2013 Macmillan Publishers Limited