What we know about energy balance

Transcription

1 What we know about energy balance New understanding on how and why we gain and lose weight Presented by A/Professor Amanda Salis The Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders The University of Sydney Page 1

2 Disclosure I have received payment from the following organizations for seminar presentations Shoalhaven Family Medical Centres Eli Lilly Pharmacy Guild of Australia Novo Nordisk Dietitians Association of Australia I have received payment from Nestlé Nutrition for consulting Prima Health Solutions provided in-kind clinical trial support I am the author of The Don t Go Hungry Diet (Bantam, Australia and New Zealand, 2007) and Don t Go Hungry For Life (Bantam, Australia and New Zealand, 2011) The University of Sydney Page 2

3 Overview of what we know about energy balance 1. How and why we gain weight ( meet the Fat Brake ) The early ( reversible ) phase The later ( potentially irreversible ) phase 2. How and why we lose weight ( meet the Famine Reaction ) The University of Sydney Page 3

4 1. How and why we gain weight ( meet the Fat Brake ) The early ( reversible ) phase The later ( potentially irreversible ) phase The University of Sydney Page 4

5 The Fat Brake helps to prevent / reverse weight gain set point too fat! Chemical changes in the hypothalamus fat loss fat gain Effects of the Fat Brake 1. Reduced hunger / cravings 2. Increased propensity to move 3. Increased metabolic rate? 4. Hormonal changes that promote fat loss e.g. increased thyroid function Amanda Salis 2017 Sainsbury A Journal of Eating Disorders 2014

6 High fat diet initially increases, but eventually decreases, leptin receptor expression in hypothalamus Lin et al Brain Research 2000 The University of Sydney Page 6

7 15 weeks on a high fat diet reduces leptin signaling in mice 4 Weeks on high fat diet ( HFD ) i.p. leptin 15 Weeks on high fat diet ( HFD ) i.p. leptin 15 Weeks on high fat diet ( HFD ) i.c.v. leptin El-Haschimi K J Clin Invest 2000 The University of Sydney Page 7

8 Early and later phases of weight gain In rodents, the early phase of weight gain lasts for a few months ( ~15-19 weeks ) It is not yet known. Whether the later phase is irreversible ( point of no return ) Whether the later phase of weight gain exists in humans The earlier phase of weight gain is the optimum phase in which to treat overweight or obesity World Obesity Day 2017 Treat obesity early to avoid the consequences later The University of Sydney Page 8

9 2. How and why we lose weight ( meet the Famine Reaction ) The University of Sydney Page 9

10 The Famine Reaction opposes ongoing weight loss too thin! set point Chemical changes in the hypothalamus Effects of the Famine Reaction 1. Increased hunger / cravings 2. Lethargy 3. Reduced metabolic rate 4. Hormonal changes that promote fat accumulation and lean tissue loss i. Decreased thyroid function ii. Increased cortisol iii. Decreased IGF-1 iv. Decreased sex hormones 5. Reduced libido fat loss fat regain Amanda Salis 2017 Sainsbury A Obesity Reviews 2012

11 Landmark study showing effect of an 8-week very low energy diet on hunger in people with overweight / obesity 50 people enrolled, 34 completed study, BMI 34.7 ± 3.7 kg/m 2, 8-week VLED. Sumithran P NEJM 2011 The University of Sydney Page 11

12 Sustained increase in the drive to eat after weight loss Sumithran P NEJM 2011 The University of Sydney Page 12

13 Sustained alterations in appetite regulating hormones after weight loss Sumithran P et al NEJM 2011 The University of Sydney Page 13

14 Hunger levels significantly increased over baseline even at 3 years after weight loss! Purcell K et al Lancet Diabet Endocrinol 2014 The University of Sydney Page 14

15 Circulating ghrelin concentrations increased over baseline even at 3 years after weight loss! Purcell K Lancet Diabet Endocrinol 2014 The University of Sydney Page 15

16 Conjecture about the duration of reduced metabolic rate after weight loss A study from the Biggest Loser suggests it lasts for 6+ years! The University of Sydney Page 16

17 The University of Sydney Page 17

18 The University of Sydney Page 18

19 Multi modal and stepwise treatment of overweight and obesity TREATMENTS Bariatric surgery Anti-obesity pharmacotherapy Cognitive therapy Lifestyle education Severity of obesity INTENDED OUTCOMES Physical activity éenergy expenditure Lifestyle changes Negative energy balance Weight loss Health benefits Dietary changes ( types / amounts ) êenergy intake

20 Dose dependent health benefits of weight loss ( the more you lose, the more you gain [ in health ] ) Atukorala I Arthritis Care & Research 2016; Cefalu WT Diabetes Care 2015 The University of Sydney Page 20

21 Conclusions The sooner we intervene to treat overweight / obesity, the more effective it is likely to be Once overweight / obesity is established, it is exceedingly difficult to lose excess weight ( the body fights back ) Treat overweight / obesity early to avoid the consequences later ( notably the potential point of no return ) Use a multi modal and stepwise treatment strategy The University of Sydney Page 21