Links between diet and health :Links between diet and health Week 1 Diet and Obesity


Obesity – prevalence :Obesity – prevalence


Health consequences of obesity :Health consequences of obesity Obesity estimated to account for > 31,000 premature deaths / year (6%) CHD, Stroke, high blood pressure, diabetes, some cancers, arthritis Obesity costs … (national audit office) NHS > £500m a year the economy ~ £2bn a year 7% of national health budget in US


Measurement and classification of overweight and obesity :Measurement and classification of overweight and obesity BMI used as (proxy) measure of adiposity (fatness) in large scale studies = wt. (kg)/ ht. (m2) 30 = obese Other methods actually measure body composition Lean Body Mass (LBM) / Fat Free Mass (FFM) + Fat Mass (FM) % fat


Slide 5:increases progressively from 20 to 50 years of age, but begins to decline after 60 years of age. In England 21% of women, 17% of men are obese ~ 65% of men > 50% of women are obese / overweight ~ 10% of children < 4 is obese, ~ 25% are overweight


What are the causes of this trend? :What are the causes of this trend? Obesity in England increased more than 150% between since 1980 and 1997 trends paralleled within racial groups Obesity in Britain: gluttony or sloth?Prentice AM, Jebb SA.


Becoming fatter while eating less? :Becoming fatter while eating less? The only trends paralleling obesity in UK are measures of physical activity / sedentariness (not EI) Transport: car ownership in adults teenagers walking to school 59% (1986) to 49% (1996) car journeys to schools doubled. Leisure time activity: Average hrs TV doubled over 30 yrs Prentice & Jebb (1995)


Temporal Trends in energy intake (EI): “the american paradox” :Temporal Trends in energy intake (EI): “the american paradox” However, this paradox has been challenged (Stubbs & Lee 2004) US: NHANES (2004) survey of food consumption 1971-2000 - increased EI mainly from CHO Australia: ACHPER (2001) monitoring of energy intake 1983-1995 - increased EI (3-4% / 350 kJ per day) Europe: MONICA (2004) - Increased EI, EI correlating with obesity Therefore, evidence that EI has increased as well as evidence that PAL has decreased and is lower in the obese (cause or consequence?)


Slide 9:Good compliance with diet and activity program reported under-reported EI by 47% Over-reported physical activity by 51% A major problem with large scale population (and even small) studies is the accurate measurement of Energy intake (especially in obese) Energy expenditure


Epidemiological relationship between activity and BMI/body-fat :Epidemiological relationship between activity and BMI/body-fat Strong correlations between activity and %body fat, with DLW measurements BUT the relationship is weaker in females Longitudinal studies Low activity levels is associated with weight gain @ follow-up (Rissanen et al 1991)  activity predicts weight gain and  activity (walking and high intensity exercise) predicts weight loss (French et al 1994)


Chronic exercise – improved fat metabolism and weight loss? :Chronic exercise – improved fat metabolism and weight loss?


Does chronic exercise affect fat metabolism? :Does chronic exercise affect fat metabolism? in muscle ...  muscle LPL  beta-oxidative, krebs and ETC enzymes  Mitochondria Several chronic adaptations to exercise training improve breakdown (lipolysis) and utilisation (oxidation) of fats during exercise: In Adipocytes Attenuated decline in sensitivity associated with weight loss (diet)  sensitivity to lipolytic effect of catecholamines


Exercise promotes fat loss :Exercise promotes fat loss 6 months supervised training Time: 90 minutes Intensity: approximately 55% of (VO2max) Frequency: 4-5 times a week for a period of 6 months. FAT LOSS eg. Lamarche et al 1992 Average = 0.7 KG (1.6 lb) Average weekly fat loss = 0.05 kg (


Reviews of exercise and weight loss research :Reviews of exercise and weight loss research Epstein and Wing (1980) Average WL = 0.1 kg/ wk Wilmore (1983) Average WL = 0.07 kg/ wk Ballor and Keesey (1991) Males walking-running / cycling ~ 0.11 kg / wk Females lower loss and negligible with cycling Garrow & Summerbell (1995) Average WL : Males = 3.0 kg 30 wks = 0.1 kg/wk Females = 1.4 kg (12 wks) = 0.15 kg/wk The failure to detect a beneficial effect of exercise on body weight may be related to poor compliance with an exercise program.


Compliance problems … :Compliance problems … Hughes 2003 WHO recommended activity levels for 4 wks (1.5 MJ / d) overweight males and females 1.1 kg predicted BW loss NO change in BW or composition 2/ 3 of subjects completed study 70% achieved prescribed levels of exercise


“A little effort, a great result” ?! :“A little effort, a great result” ?! “overweight group appeared to be both insufficiently fit and / or motivated to achieve their exercise goals” (Blundell et al 2003) “formal exercise of limited duration, in and of itself, is not a major factor in weight loss,” (Lamarche, 1992) “Exercise in the treatment of obesity - a marginal contribution” (Garrow 1995)


Consensus statement (2003) :Consensus statement (2003) Weight loss Short-term studies ( controls (no ex or diet) Ex + diet 0.1 kg > diet alone Long term (> 26 wks) Exercise only 0.04 kg / wk > controls Ex + diet 0.02 kg > diet alone BUT body composition changes not always measured and good evidence that composition of weight loss altered by exercise particularly resistance exercise


Hansen et al 2007 – meta analysis :Hansen et al 2007 – meta analysis Results 21 studies reviewed - only 4 showed results that diet and exercise increased fat-mass loss over diet alone 19 studies reviewed – no real difference in the exercise modality (all a bit crap) Conclusion Agree that exercise does not induce any greater fat loss that dietary interventions Promotes healthy lifestyle choices May improve visceral and gluteal / femoral fat depots – which is associated with improved insulin sensitivity. Low intensity exercise to improve compliance.


Slide 19:Only 1 found a small statistically significant, difference in weight loss with diet + exercise than with diet alone. Results from 6 studies comparing short-term (4-6 months) diet alone with diet + exercise


Body composition changes with diet and exercise (Kraemer et al 1999) :Body composition changes with diet and exercise (Kraemer et al 1999)


Fat: the cost of losing it :Fat: the cost of losing it REMEMBER 1kg of fat = ~ 7000 kcal If 75 kg female walks 1 mile she would expend 100 kcal Therefore 1 kg fat loss requires a total of ~ 70 miles of additional walking assuming no dietary compensation


Weight and Diet Intake :Weight and Diet Intake


Energy Balance – is intake more important than expenditure? :Energy Balance – is intake more important than expenditure? Jebb (2002) Christmas Marathon Day in bed Starvation


Meal Replacement Treatment of Obesity :Meal Replacement Treatment of Obesity US study – 6 sites showed: Men ↓ 17 pounds (7.8kg) over 12 weeks Women ↓ 17 pounds over 24 weeks Compliance = 50% At 104 weeks weight loss was maintained German Study – compared meal replacement against reduced portion sizes: Kcal was equal in groups, however compliance may have been the difference Meal replacement ↓ 16 pounds (7.3kg) over 12 weeks Reduced portions ↓ 3 pounds (1.4kg) – 12 weeks p < 001 Heber (2002) ‘Meal Replacements’ are defined as functional foods in the form of drinks or bars meant to replace a meal


Very Low Calorie Diet (<800 kcal/d) :Very Low Calorie Diet (<800 kcal/d) Study of women 12 – 16 weeks of treatment showed 20-25% greater losses than a 1000 – 1500 kcal/d diet. However in six different studies after a year there were no significant differences between VLCD and 1000-1500 kcal/d diets. Wadden (2002)


End of sessionFor next week…..Research the….Study of health outcomes of weight loss (SHOW) trial :End of sessionFor next week…..Research the….Study of health outcomes of weight loss (SHOW) trial