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Weight Loss Physiology: Emphasis on Metabolic AdaptationEric Ravussin, Ph.D
Minimally Invasive Surgery SymposiumFebruary 21-26, 2011; Salt Lake City, UT
Major Testing Wk 52Outpatient visits x x x x x x x x x x x x x
-6 to -1 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56
* LCD subjects will have weekly outpatient visits from the beginning of the LCD diet until the inpatient assessment at week 7Weeks
Study Groups
SCRE
ENING
BASE
LINE
Roux-en-Y-Gastric Bypass (RYGB)
Sleeve Gastrectomy (SGx)
Gastric Banding (GBa)
Low calorie diet induced weight loss (LCD)
Surge
ry Wk 7
Funded by Ethicon Surgery
Goal: 48 subjects (12/group)
n=1
n=2
n=4
n=4
BARIA Study
• Energy Balance vs. Substrate Balance• Metabolic Adaptation• Bariatric Surgery: Energy Metabolism in Animal
Studies• Bariatric Surgery: Energy Metabolism in Human
Studies
Weight Loss Physiology: Emphasis on Metabolic Adaptation
Etiology of Overweight and ObesityThe Energy Balance Equation
Genes
Environment
Gain Stable Loss
Intake
Expenditure
Body Weight
Energy Intake (EI) = Energy Expenditure (EE) ± Body Energy Stores (S)
S ≈ body weight (W)
Energy Balance Equation in Response to Overfeeding or Caloric Restriction
Going from stable energy balance to 500 Kcal/d negative energy balance is not as simple as 1 pound of weight loss a week (¾ FM and ¼ FFM) because:
- The energy content of weight change is not constant- The fraction of weight loss as FFM is not constant- Energy expenditure changes in response to weight loss
Body Weight Simulatorshttp://www4.niddk.nih.gov/lbm/ (Kevin Hall; NIDDK)Web-based dynamic simulation model of adult human metabolism that predicts the time course of individual body weight change in response to a prescribed behavioral intervention.
http://pages.csam.montclair.edu/~thomasd/BodePlot.html (Thomas/Heymsfield)
Not to Do with Data from Energy BalanceAnd Energy Expenditure
• Energy Balance• Do not extrapolate an Energy Gap (kcal/d) over time• The rule of 1 pound of weight loss a week for
500kcal/day deficit is wrong
• Energy Expenditure• Do not divide VO2 (EE) by body weight• Such a division introduce a mathematical artifact
Body Size (Wt, FFM, BSA…)
VO2 (EE)
Range > 60,000 kcal
Energy Stores
Fat 125,000 kcal
Protein 40,000 kcal
Carbohydrate 2,000 kcal
Oxidation
as % stores
0.8
1.3
50
Intake
as Total Kcal
1,000
500
1,000
Daily Nutrient Balance (70kg Man; 20% Fat) on 2500 kcal/d Diet
(40% fat, 40% CHO , 20 % Protein) Range for up to 150-kg Man
Fat Intake = Fat Oxidation; Prot Intake = Prot OxidationCHO Intake = CHO Oxidation; Alcohol Intake = Alcohol Oxidation
Flatt JP, IJO July 1996
Regulation of Nutrients Balance: FQ/RQ Concept
Fat intake is poorly regulated because of the relatively small daily flux relative to the large pool size
Fat Balance vs. Energy Balance
Abbott WGH, et al. AJP 1988;255:E332-7
• Energy balance is buffered by fat balance
• Positive energy balance = fat gain
• Negative energy balance = fat loss
Variability in Respiratory Quotientand Impact on Weight Gain
Zurlo F, AJP 259:E650-E657, 1990
Cum
ulat
ive
Inci
denc
e of
a5
kg B
od
y W
eig
ht
Gai
n (
%)
Energy Bal% Body Fat
Sex
WithinSubject
Method
Per
cen
tag
e o
f E
xpla
ined
Var
ian
ce
40
20
0
Duration of Follow-up (years)
0 0.5 1 1.5 2 2.5 30
20
40
60
80
high RQ > 0.87
Low RQ < 0.82
Family
• Energy Balance vs. Substrate Balance• Metabolic Adaptation• Bariatric Surgery: Energy Metabolism in Animal
Studies• Bariatric Surgery: Energy Metabolism in Human
Studies
Weight Loss Physiology: Emphasis on Metabolic Adaptation
Extreme weight loss typically observed only after bariatric surgery
39.6%
Ciangura et al. Obesity 2010
3 6 12
-40
-30
-20
-10
0
Fat-free mass
Fat mass
Wei
gh
t L
oss
(kg
)
-20 kg
-30 kg
-37 kg
60%
40% 32% 30%
68%70%
Months following gastric bypass
60% loss of excess body weight
Buchwald et al. Am J Med. 2009
Loss of substantial lean mass considered detrimental
Does exercise attenuate fat-free mass loss and decrease metabolic
adaptation during weight loss?
Very-low calorie diets (including surgically-induced) result in rapid weight loss with substantial loss of FFM
Limited data suggests that exercise may preserve lean tissue during significant weight loss
QuestionWhat are the effects of large weight losses
(mediated through extreme exercise plus calorie restriction) on body composition and metabolic
adaptation?
Participant Characteristics
Baseline Week 6 bl to wk 6 Week 30 bl to
wk 30
Weight (kg) 145 (110-215) 130 (95-194) <.001 87 (60-138) <.001
BMI 48.7 (40.7-72.8) 43.6 (37.2-65.7) <.001 29.3 (22.2-46.8) <.001
Fat (%) 49 (36-57) 46 (33-54) NS 27 (13-43) <.001
FM (kg) 71 (52-122) 59 (42-104) <.001 24 (11-60) <.001
FFM (kg) 74 (50-104) 71 (48-98) NS 62 (47-84) <.001
Age: 36 years (20-56 y old)4 males, 7 females
Johannsen et al, in review, 2011
-100
-80
-60
-40
-20
0
Exce
ss w
eigh
t Los
s (%
)Intensive “Lifestyle Intervention”
Resulted in Conservation of Lean Mass
Week 6 Week 30
-19 ± 3 %
-73 ± 16 % -60
-50
-40
-30
-20
-10
0
Fat massFat-free mass
Wei
ght l
oss
(kg) -15 ± 5 kg
-58 ± 25 kg
80% 19%
81%
Week 30Week 6
Johannsen et al, in review, 2011
1500
2000
2500
3000
Resti
ng
meta
bo
lic r
ate
(kcal/d
ay)
Predicted RMR = 1,241 + 19.2 FFM + 1.8 FM – 9.8 age + 405 (male)
Metabolic Adaptation Occurs despite Lean Mass Preservation
Baseline Week 6 Week 30
p<0.001p=0.006
-244 ± 231 -504 ± 171
Johannsen et al, in review, 2011
The Metabolic Adaptation Occurred Early in the Intervention
40 60 80 1001000
2000
3000
4000Week 6
Week 30
Baseline regression line
Fat-free Mass (kg)
Res
tin
g m
etab
olic
rat
e (k
cal/d
ay)
Johannsen et al, in review, 2011
Determinants of the Metabolic Adaptation
CR
↓ leptin
↓ Gonadal axis ↓ SNS ↓ Thyroid hormones
↓ Energy metabolism = metabolic adaptation
Correlation between change in leptin and RMR residual in BL (7 mo) and GB (12 mo) participants
Johannsen et al, in review, 2011
Summary and Question
• An intensive lifestyle intervention (vigorous daily exercise and self-selected calorie restriction) results in extreme weight loss with preservation of lean mass
• Despite the preservation in lean mass, significant metabolic adaptation occurred
Does a similar “Metabolic Adaptation” happen after bariatric surgery?
• Energy Balance vs. Substrate Balance• Metabolic Adaptation• Bariatric Surgery: Energy Metabolism in Animal
Studies• Bariatric Surgery: Energy Metabolism in Human
Studies
Weight Loss Physiology: Emphasis on Metabolic Adaptation
RYGB induces substantial increase in EE in rats
RYGB rats have:
1) Decreased body weight
2) Increased total and resting oxygen consumption
3) Lower RQ
Stylopoulos, Obesity, 2009
RYGB-stimulated increases in EE are dependent on food ingestion
RYGB rats have:
• Higher resting V02 during ad lib refeeding and not during fasting
• Higher core body temperature
Stylopoulos, Obesity, 2009
Zheng, Am J Physiol Regul Integr Comp Physiol, 2009
RYGB rats have higher RER
Energy Balance:Emphasis on Metabolic Adaptation
with Bariatric Surgery
• Energy Balance vs. Substrate Balance• Metabolic Adaptation• Bariatric Surgery: Energy Metabolism in Animal
Studies• Bariatric Surgery: Energy Metabolism in Human
Studies
Decreased measured and predicted REE after RYGB in 20 obese women
Bobbioni-Harsch, JCEM, 2000
Increased fat oxidation after RYGB in 20 obese women
Bobbioni-Harsch, JCEM, 2000
Metabolic adaptation occurs with surgically-induced weight loss
0
500
1000
1500
2000
2500
RM
R (
kcal
/day
)
20
25
30
35
40
RM
R/F
FM
(kc
al/k
g)
Baseline Month 6
-396 ± 157 kcal/dp<0.001
-3.3 ± 3.6 kcal/kg FFMp<0.05
Fat-free mass (kg)
RM
R (
kcal
/day
)
Values of RMR relative to FFM at baseline (regression line) and month 6 post-surgery
Carrasco et al. Obes Surg. 2007
Ratio of REE/FFM was reduced from 33.4 to 30.1 kcal/kg (P<0.05)
RQ decreased from 0.86 to 082 (P<0.05)
Van Gemert, IJO, 2000
TEE and SMR are decreased after vertical banded gastroplasty (8 obese)
Lipid oxidation is increased after vertical banded gastroplasty in 8 obese subjects
Van Gemert, IJO, 2000
Conclusions from Human Energy Metabolism Data after Bariatric Surgery
(Bypass)
• Generally, gastric bypass seems to decrease the magnitude of the metabolic adaptation
• Gastric bypass seems to increase lipid oxidation
Question?What are the mechanisms underlying the favorable energy metabolism profile after
gastric bypass?