What is Metabolic Flexibility? Linda McCargar PhD RD. Nutrition Forum, Vancouver, BC June 8 th, 2011

Transcription

1 What is Metabolic Flexibility? Linda McCargar PhD RD Nutrition Forum, Vancouver, BC June 8 th, 2011

2 Background: Body composition and energy expenditure. weight cycling evaluation of nutrition and physical activity interventions school health projects disease states

3 Background: Energy Expenditure influences on metabolism factors influencing hypo or hyper-metabolic rate. can diet alter metabolism

4 Energy Expenditure Assessment

5 Nutrition 101 REE resting energy expenditure 1 hour measurement: 30 min rest/30 min test TEF thermic effect of feeding: estimate 7% TEE thermic effect of exercise: calculation based on self-report. Total EE = REE* + TEF + TEE RQ = CO2/O2 (at rest*) <0.82 * measured

6 We need 24 hours of measurements 24 hour Total EE = measured REE + TEF + TEE 24 hour RQ = to assess metabolic flexibility

7 1. What is Whole Body Calorimetry? 2. What is Metabolic Flexibility? 3. Importance of and application for measurement of metabolic flexibility.

8 1. What is Whole Body Calorimetry? A sophisticated research suite for non-invasive evaluation of energy balance. All activity within the suite is carefully monitored through changes in O2 and CO2. Study participants typically live within the suite for 1-3 days depending on the goals of the study. All food is weighed and measured.

9 The suite is a room within a room with an external corridor providing space for equipment and instrumentation of the unit. There are precise controls/sensors for maintaining temperature, humidity, and air flow; and analyzers for O2 and CO2.

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12 2. What is Metabolic Flexibility?. the capacity of the body or cells to match fuel oxidation to fuel availability and the endocrine environment. 1 In theory carbohydrate intake should = carbohydrate oxidation = RQ fat intake should = fat oxidation = RQ 1 Gaglani and Ravussin Int J Obes 32:(S7)S109, 2010.

13 How flexible are we? Although rarely occurring. If only carbohydrate was oxidized for energy RQ = 1.0 If only fat was oxidized for energy RQ = 0.70 Typically, humans are almost always using various proportions of cho/fat for energy; and protein is being preserved and used for other functions.

14 Measurement of Metabolic Flexibility The increase in RQ from fasting to glucose/insulin stimulated conditions. The reduction in RQ after an overnight fast. The macronutrient oxidation adaptation with isoenergetic changes in diet composition. Gaglani et al. Diabetes 57:841, Ukropcova et al. Diabetes 56:720, 2007.

15 Changes in Diet Composition If macronutrient intake changes, macronutrient oxidation should change to re-establish a new equilibrium. Rate of adaptation varies: with diet 1 : adjustment of low cho high cho(~ 2 days) low fat high fat (~1 week) with individual: large inter-individual variability 1 Schrauwen, Westerterp. Brit J Nutr 84:417, 2000

16 Macronutrient Equilibrium Appears to be particularly difficult in people with: low fat oxidation low energy expenditure low sympathetic activity low spontaneous physical activity (fidgeting) (all increase the tendency to gain weight). 1 Gaglani and Ravussin Int J Obes 32:(S7)S109, 2010.

17 Carbohydrate Balance is the Key Small storage capacity Important role of carbohydrate in most tissues and organs Carbohydrate balance must be maintained

18 3. Importance and Application of Metabolic Flexibility Measurement Obesity/Diabetes Sarcopenic Obesity

19 Obesity/Diabetes An inefficient switch between carbohydrate and fat utilization, may play a key role in insulin resistance, diabetes, obesity and/or metabolic syndrome where fat accumulation in organs and tissues is problematic. Metabolic (in)efficiency has been implicated in intramuscular fat accumulation and insulin resistance. 1 1 Gaglani et al. Am J Phys Endo Met 295:E1009, 2008

20 Obesity/Diabetes: The Overnight RQ Drops Transition from fed to fasted state. More fatty acids utilized for energy and RQ drops. Impairments reported in: People with family history of diabetes (1, 2). Obese people with insulin resistance (3). Adults with T2D (4). (1) De Pergola et al Diab Nutr Metab 16:41, 2003 (2) Lattuada G et al Diabetologia 48:741, 2005 (3) Kelley et al. Am J Phys Endo Met 277:E1130, 1999 (4) Kelley, Simoneau J Clin Invest 94: 2349,1994.

21 Planned Investigation: Diabetes Study for Fall patients with T2D Stay in the unit 24 hours on 2 occasions Assess their metabolic response at rest, postprandial, during and after exercise, and while sleeping. Compare to age, sex, BMI, matched controls for metabolic flexibility.

22 Sarcopenic Obesity confluence of two epidemics: the aging and the obesity epidemics Roubenoff. Obesity Research 12:887, 2004

23 Prevalence Prevalence (%) "Normal" Obese Sarcopenic Sarcopenic obese 0 < > 80 Age- group (years) Baumgartner. Ann. New York Acad Sc 904:

24 Planned Investigation: Sarcopenic Obesity In sarcopenic and non-sarcopenic obese: Measurements of: -body composition -24 hour energy expenditure -cytokines -glucose/insulin/fatty acids

25 Conclusions 1. Metabolic flexibility measurement is another tool to understand the complexity of obesity. 2. It is speculated that low fat oxidizers are more susceptible to weight gain. 3. Maintaining carbohydrate balance appears to be an important goal. 4. Diet modification targeted to one s s metabolic flexibility or (in)flexibility( may improve macronutrient balance, and subsequently energy balance.

26 Acknowledgements Funding for the calorimeter: Advanced Education and Technology, AB Gov t; Knowledge Infrastructure Program, GOC; Funding for the Diabetes study: AB Diabetes Foundation/AB Diabetes Institute.