Lecture2122r.pdf

Obesity IV Appetite: The psychology of eating and drinking 1 1 Treatment and body image • In this lecture we will conclude our examination of treatment options for obesity – – – – Exercise Behaviour therapy Drugs Surgery • We will then turn to a related topic, that of body image and weight cont...

Obesity IV Appetite: The psychology of eating and drinking 1 1 Treatment and body image • In this lecture we will conclude our examination of treatment options for obesity – – – – Exercise Behaviour therapy Drugs Surgery • We will then turn to a related topic, that of body image and weight control in healthy weight people 2 2 Exercise I • Regular physical exercise offers a number of benefits in treating obesity • It may increase weight loss • It improves, independent of weight loss, glucose tolerance, blood pressure and lipids • It increases lean body mass • It likely improves long-term dietary compliance • It improves mood and may alleviate depression • Regular exercise is the best predictor of long-term weight loss • It decreases morbidity in physically fit obese/overweight • What “dose” of exercise is useful? • CDC and the US Surgeon General suggest 30 mins of moderately intense physical exercise per day (brisk walk) • I of Medicine and IAS of Obesity suggest double this 3 3 Exercise II • What constitutes moderate intensity exercise? – Strict definition is exercise that raises your heart rate (HR) to 55-69% of your maximal HR – Maximal HR = 220 – Age – So for a 20 year old… (220-20) x 0.55 (and to 0.69) = target would be 110138 beats/min – More casual definitions… • Moderate intensity (55-69%) – can hold conversation, but not sing and noticeable increase in HR and breathing rate • High intensity (70%+) – can only talk in short phrases and HR is substantially increased as with breathing rate – Calculating your fitness level • Time how long it takes you to walk 1 mile (level – no hills; 1.64km) as quickly as possible and at the end take your heart rate • Then plug these values in at… http://www.brianmac.co.uk/rockport.htm and this will give you a rough idea of your VO2 – basically, a measure of how efficient your body is at getting oxygen to your muscles 4 4 Exercise III • 70-75% of adults do not meet even CDC guidelines for exercise • Both healthy and obese individuals find it difficult to: • Initiate exercise (motivation, busy, not enough time, too tired, too lazy, too inconvenient) – The more such reasons reported the more likely it is they will not initiate an exercise program • Maintain a program of exercise • Both of these can be ameliorated by • Behaviour therapy (discussed next) • Lifestyle programs, which attempt to embed physical activity within peoples daily lives – Intermittent activity – Pedometer (10,000 steps program [2000 = 1 mile]) 5 5 Behaviour therapy I • Almost no obesity intervention is now without this component • The aim is to identify the behavioural factors which promote problem behaviours (e.g., overeating) and prevent uptake of healthy behaviours (e.g., exercise) • It does this through: – Identifying appropriate GOALS – Identifying how to achieve them • Designing small incremental changes (shaping) 6 6 Behaviour therapy II • Treatment components • Self monitoring (detailed diary of food intake, exercise etc) – Reveal hidden patterns that the person is unaware of – Confront the person with what they are actually eating (some studies indicate 50% under-reporting in the obese) – Such self-monitoring correlates with long-term weight control • Stimulus control (identifying cues to eating) – Involves simple premise of out of sight out of mind (+ reverse) » Put food away, serve small portions, no extra food on table, and remove uneaten food ASAP • Cognitive restructuring (“I’ve blown my diet, so I might as well stuff my face” to “this is just a lapse - not a disaster”) – Uses role playing to deal with such situations – Addresses achievable weight loss goals and fear of failure • Time limited therapy sessions – Group format superior to individual format 7 7 Behaviour therapy III • Behaviour therapy in association with dieting is significantly better than diet alone in the short term • More weight is lost (5-10% vs 5%) • Compliance is better (at around 80%) • The benefit of behaviour therapy for long term weight loss is not currently known • People tire of repeated clinic/therapy visits • Phone/internet/email contact with the therapist may facilitate longer-term maintenance of weight gains - this is disputed by some 8 8 Medication I • The history of drug treatment for obesity is not very reassuring… • Amphetamines - dependence/tolerance – not used for obesity treatment since the 1970s • (Withdrawn 1997) Dexfenfluramine/Fenfluramine - side effects (pulmonary hypertension) – But lower incidence than first thought – Dose and time dependent – May remit in some individuals • (Withdrawn 2009) Rimonabant – increased risk for anxiety, depression and suicide • (Withdrawn 2010) Sibutramine – increased risk for heart attack and stroke • However, medication has one major advantages over the other treatment regimes we have looked at so far • It is far less reliant upon self-control 9 9 Medication II • There are currently two main approaches • Centrally acting drugs (approved or likely to be approved) – – – – – Phentermine (amphetamine derivative) (New use) Topiramate (anticonvulsant; used in combination with Phentermine) (New drug) Lorcaserin (fenfluramine derivative – similar efficacy to Phentermine) (New use) Liraglutide (originally for type II diabetes but results in weight loss) (New combination) Naltrexone and Bupropion (used to manage food cravings) • Peripherally acting drugs (approved or likely to be approved) – Orlistat (inhibits pancreatic lipase) – (New drug) Cetilistat (derivitive of orlistat) • To be classed as effective, medication needs to reduce weight by more than 5% (FDA) or 10% (EMA) - relative to placebo • This is a highly contested issue as approval depends upon a drug meeting the FDA/EMA effectiveness criterion, so there is an incentive to make the placebo control condition as ineffective as possible • It is then possible (perhaps even likely) that many approved weight-loss drugs may be no more effective than really well-designed weight loss programs (i.e., diet, behaviour therapy, exercise etc) 10 10 Centrally acting drugs • Phentermine (trade names Duromine & Metermine) • Phentermine and its derivative medications (diethylproprion, phendimetrazine, benzaphentamine) have been used for over 50 years and are the most widely prescribed weight loss drugs • Several clinical trials have established their efficacy (around 5% at 1 year) and they are all well tolerated • Phentermine exerts its therapeutic effect via the hypothalamus, where it binds to TAAR1 receptors causing synaptic release of various monoamines – the consequence is to reduce hunger – Phentermine also affects peripheral fat cell metabolism • Phentermine may now be prescribed with topiramate, which together produce greater weight loss than either alone (around 9% at 1 year) – Topiramate has a harsher side-effect profile than phentermine (impaired cognitive function, psychomotor slowing, paresthesias) • Over 1 year, effectiveness plateaus and some weight-regain may occur, this is a common feature of all weight loss drugs 11 11 Peripheral drugs • Orlistat (tradename Xenical) • Orlistat blocks pancreatic lipase resulting in a failure to digest fat • Around 30% of ingested fat is not digested (excreted) • The adverse consequences of eating lots of fat whilst taking Orlistat are highly aversive • Orlistat also produces weight-loss independent improvements in blood lipids • It is not licensed for long-term use and anyway most people could not tolerate it longer term (with high drop out rates in clinical trials due to its side-effect profile [fecal incontinence & urgency]) • It has a weight loss efficacy less than Phentermine (around 3-5% at 1 year) • Cetilistat has an improved side-effect profile but there is not as yet an extensive database of clinical trials to determine its efficacy 12 12 Surgical treatment • Two types of procedure are generally available either alone or in combination • Restrictive procedures – Gastric banding • In this case the volume of the stomach is reduced to 30cc by staples or banding • The benefits of this approach depend upon patient compliance (drinks!) • Effectiveness at 1 year is weight loss of 30-50% of initial body weight • Low morbidity and reversible • Side effects – Gastric reflux & vomiting; Solid food intolerance; Stenosis of surgical stoma; Ulcers & hernia – Vertical sleeve gastrectomy • Restrictive, irreversible, but with additional benefits (similar to Roux-en-Y) • Performed laparoscopically • Effective in children (no growth slowing) 13 13 Surgical treatment • Malabsorptive procedures – Shortening of the small intestine (SI) • Here a varying length of the small intestine is bypassed so that food simply can not be digested. This procedure is now not generally used – Roux-en-Y gastric bypass (REGB) REGB • This involves a threefold process – The stomach is reduced in size – The new stomach pouch exits into the SI (one arm of the Y) – The old remnant of the SI from the stomach is connected to the new SI connecting arm forming the other arm of the Y • The small pouch limits meal size • The smaller SI length restricts absorption of food • The food remains longer in the SI before it encounters bile/pancreatic juices from the other arm of the Y • Dumping syndrome occurs if sugars/fats are eaten to excess • Rapid benefits to Type 2 Diabetes & alteration in food prefs – Endobarrier 14 14 Roux-en-Y gastric bypass • At 1 year patients have typically lost 50-60% of their initial body weight • This is maintained for at least 14 years - but there is a catch • Such patients need continuous medical supervision – – – – X-ray contrast 1 day post surgery (leaks) Liquid diet for 2 weeks Soft solids for 6 weeks By 3 months varied diet - but several small meals and water in between to minimise side effects – 6 monthly follow-up for ever, along with dietary supplements and vitamin B12 injections • This surgical treatment is the ‘gold-standard’ approach, but is rapidly being superseded by the sleeve gastrectomy 15 15 Weight loss • So far we have considered weight loss primarily in obese individuals • However, surveys repeatedly indicate that a majority of men and women wish to lose weight and that many repeatedly try to do so (consistently around 60-70% of respondents) • Clearly some of these individuals are overweight, but many are not, so what spurs people to want to lose weight? 16 16 Body dissatisfaction • One major factor which has been identified as important, is dissatisfaction with what one imagines one looks like – That is body image dissatisfaction • This comes in three forms in normal weight people: • As a distorted body image - “I am fat” • As a discrepancy from an ideal - “ I think I am larger than I would like to be” • As a generally negative appraisal of ones body - “I don’t like my body” 17 17 Body dissatisfaction Perceptions of body image can be measured in several ways – Projection measures (e.g. adjust spots to represent hip size and compare to actual hip size) • Most people (especially women) overestimate their size • This effect is most pronounced in those with an eating disorder – Computerised morphing measures (self & other) – Perceived vs ideal body size/shape (see below) • Which one do you resemble VS which one you would like to look like – Negative thoughts about the body (questionnaires) • Body shape questionnaire; MD Body Self Relations Questionnaire 18 18 So who is dissatisfied? • Many women (50-75% percent) – – – – 55% with their weight overall 57% with their stomach 50% with their legs 32% with their breasts • Some men (30%+) – Tendency to focus on muscularity (especially upper torso) – Evidence strongly suggest increasing body dissatisfaction • Body dissatisfaction (BD) appears in females at 8 or 9 and is consistent across the lifespan • BD is more common in Westernised nations • BD appears more common in higher SES groups • BD also increases in migrants as they acculturate 19 19 So why are people dissatisfied? • The media (TV, magazines etc) – Thin women and muscular men are portrayed as ‘the norm’ – Of course, the population at large is not like this and there is considerable evidence that the media is highly non-representative in its portrayal of ‘normality’ – Experimentally, showing men or women such thin or muscular figures increases their body dissatisfaction • This effect occurs in normal weight, anorexic, bulimic and pregnant women • Relatedly, seeing images of obese individuals improves body satisfaction – If these effects occur for such acute exposures, imagine what chronic exposure may do… • But pause to reflect on a seeming paradox here; while people watch a lot of media, they also see plenty of ‘real’ people (the majority of whom are overweight/obese), so why doesn’t this balance it all out? 20 20 Portrayal of body forms on US TV Men TV Women Reality TV Reality 21 21 So why are people dissatisfied? • The family – Daughters tend to reflect their mother’s level of body dissatisfaction – This could result from mothers and daughters sharing similar physiques and so experiencing similar social pressures • Cause? – Likewise, the media could simply be responding to what they believe the public desires, but the fact that exposure to such images produces increased body dissatisfaction suggests a causal role 22 22 Body dissatisfaction in perspective • Our current preoccupation with‘thinness’ (and diet) may represent yet another attempt to shape the female (and increasingly) the male body, towards some sexual ideal • Interestingly when asked, both normal weight, overweight and obese individuals report that physical attractiveness (not health) is the primary motive for losing weight • We can see all of this more clearly if we look at some historical examples of how a sexual ideal can shape the human body form - especially the female form - in what now appear bizarre ways • Notice that in most of these examples they involve exaggerating extant differences between genders 23 23 Fashion and the body - Foot binding “If you care for your son don’t go easy on his studies - if you care for your daughter, don’t go easy on her footbinding” (Old Chinese Proverb) – Female Chinese children until the 1930’s had their feet bound so as to produce a ‘lotus hook’ (see R.) – The ‘lotus hook’ was an object of considerable sexual desire, but left the woman severely disabled – “The lotus has special seductive characteristics and is an instrument for arousing desire. Who can not resist the fascination and bewilderment of playing with and holding in his palms a soft and jade like hook” 24 24 Fashion and the body - Corsets • Corsets – A tiny waist was the ideal in Victorian times – In addition, doctors believed that women’s backs were weak and needed support – This led to the corset – The corset often led to impaired breathing and fainting fits, further reinforcing medical notions of female weakness – Some women even had their lower ribs removed so that the corset could be laced tighter 25 25 Slimness, Bikinis and the 60’s • The 60’s saw the advent of the women's movement • Part of this liberation included freedom from the bra and other artificial means of supporting (controlling) the body • Similarly, the 60’s saw the advent of the bikini, which hides little • Whilst leading 60’s fashion models such as Twiggy (see R) may have had no need for controlling their flesh, for many women dieting was now the only means to control their body and conform to the fashion ideal of the day (and today) • Some see these factors as the genesis of modern mass dieting in women 26 26 The psychology of dieting • Because of the increasing proportion of people who diet, more attention has been paid to the psychological consequences of dieting • A central concept in this regard is ‘Restrained eating’ • According to researchers in this area, body dissatisfaction leads to dieting, which is seen as a conscious attempt to restrain or exert control over body size and food intake – Restraint is typically measured by questionnaire • Restraint Scale, DEBQ, 3-Factor Eating Questionnaire • Note here the similarity between the Western social ideal of individual autonomy (control over ones destiny) and the notion of control over ones weight • No wonder then that fatness is equated with a failure of self-control and is thus stigmatised on this basis 27 27 Restrained eating I • A key component of the restrained eating approach was that it offered a way to explain why in some cases dieting led to weight gain rather than loss • This might be termed the ‘what the hell’ theory and has been tested experimentally in widely cited study: – Participants (dieters vs non-dieters) are given either a high calorie preload (a chocolate bar + hi cal milkshake) or a low calorie preload (crackers + water) – Then they are asked to participate in what they are led to believe is another experiment, which involves tasting and rating ice-cream – They are told to sample as much of the ice-cream as they like as it will all be thrown away after their session is completed – This is for a set period of time and is unobserved – The DV (unknown to them) is how much ice-cream they eat 28 28 Restrained eating II • As you can see, the non-dieters compensated their intake • However, dieters showed the reverse pattern • A high calorie preload led to increased consumption relative to a low calorie preload – Further experiments using Strooplike tests revealed that these type of manipulations engage cognitions directed against selfimposed food restriction - “what the hell!” • A caveat… The effect (right) is not always replicable, which may relate to measurement of restraint amongst other things Non-dieters LO HI Dieters LO HI 29 29 Restrained eating III • As we know restrained eating certainly does not always lead to over consumption as some dieters do lose weight permanently • However, many dieters do ‘fail’ and gain weight and restrained eating may offer one explanation as to why this happens - but it is not the only explanation • In fact we have already looked at several other reasons why diets may fail - in a medical setting - and these apply equally here (e.g., length of time on the diet…) 30 30 Conclusion • Acceptance of a body size which is healthy, irrespective of societal norms, should be seen as a more desirable goal than a loosing battle against ones physiology • How do you teach people to accept their bodies, but on the other hand to feel motivated to avoid becoming obese with its associated health risks? • This is a major problem without an easy solution 31 31 Starvation Appetite: The psychology of eating and drinking 32 32 Introduction • In this lecture we will consider the sociopsychobiology of starvation – – – – – Demographics Famine Physiological effects Psychological effects Lifespan extension 33 33 Demographics • How many people are currently malnourished and where are they? – World population is 7.6B and roughly 1B are malnourished • • • • • Estimates vary and severe malnourishment may cover - 0.5-20% (total pop.) Milder forms – up to 50% (total pop.) Even in the USA malnourishment may affect 0.5 Million children Children may be the most adversely affected (school attendance; biological effect on IQ) Asia and Africa have the highest incidence (green and especially blue areas below) 34 34 Some definitions • Malnourishment may be chronic or acute – Chronic malnourishment in children can cause stunting (defined as height for age is greater than 2 SD below Mean) – Acute malnourishment in children/adults causes wasting (as does chronic malnourishment in adults) • Chronic malnourishment is the norm, with exacerbations (acute) under times of famine • Famine typically does not occur in a vacuum, it usually occurs within the context of on-going societal problems • Famine inevitably concentrates every ones mind, as it is highly visible (if one can look) • Consequently, famine has been well studied 35 35 Famine – An historical perspective • Europe – Since the Roman invasion 190 famines in England - last in 1620 – Last famine in Ireland, 1846-51 – not one that history could forget! – By the mid 1800’s famines were largely ‘history’ here except for WWII • Dutch famine ‘44 [20K], Leningrad siege ‘41-44 [1-1.5M] • Asia – 90 Major famines in the last 2500 years – 66% of these have occurred since 1700 – Some of the worst have occurred in the last 50 or so years • China (1959-61), 15-43 M dead (political; the ‘difficult three-year period’). Land collectivisation, chaotic management, USSR pseudoscience [close planting, deep ploughing, killing birds], plus floods & drought led to one of the world’s worst famines • Bangladesh (1974), 1 M dead (flooding) • North Korea (1996), 0.2-3.5 M dead (political; the ‘arduous march’) • Africa (a similar picture to Asia) (e.g., Sudan ‘98, 70K) • The picture is not all doom and gloom – After WWII, the number of people per year living in famine afflicted areas was 790M, this has consistently declined over the years to less than 200M now 36 36 Chronic malnourishment in kids Stunting in 2-5 year olds 37 37 Chronic malnourishment in adults 38 38 Famine - Types & Theories • Theories of how famines come about can be broadly categorised into two • Those that emphasise human catastrophes • Genocide, war, preexisting social unrest, unstable social structures, poverty, poor government, poor communications • Those that emphasise natural catastrophes • Plagues, tempests, flooding, drought • Pure examples of either are rare, as both factors generally combine • Great Chinese famine is one example. The Irish potato famine is another – Absentee landlords, British indifference, sole reliance on the potato combined with potato blight... 39 39 Consequences of famine • The social trajectory of famine – The moral economy (i.e., sources of informal support) – Agrarian workers and landlords/employees – Relationship to family, neighbour, tribe – Religion – – – – – Reduced food intake and meal spacing Use of wild foods (frogs, rats, seaweed, grass…) Sale of non-essential possessions (cooking gear) Sale of all possessions (farming implements, land) – The PNR Migration • To cities/towns (slum-dwelling) and refugee camps – High morbidity from unclean water - GI tract infections - aided by reduced immune function from malnourishment 40 40 Physiological effects of famine • Famine affects people in different ways – Children suffer because they require far more protein than adults – The health of the foetus may be adversely compromised which may have demographic consequences decades later – Deaths usually first hits the elderly, infants, then adult males – Women and older children are often the last to die • We will now look at the effects of famine on children, pregnant women and adults… 41 41 Children • PEM (Protein/Energy malnourishment) • PEM has two extremes • Marasmus (defn: wasting away) results from a diet insufficient in calories (energy) • Kwashiorkor (defn: ‘the disease a baby gets when a new baby is born’ – from the Ivory Coast, W. Africa) results from a diet sufficient in calories, but insufficient in protein • In a famine children will typically fall on a continuum between these extremes 42 42 Marasmus (calories) • Symptoms • Extreme underweight for age (60% below the 50th percentile) • Irritable, crying, apathy • Wizened, shrunken • Chronic diarrhea • Treatment/outcome • Refeeding and hydration • Opportunistic infection 43 43 Kwashiorkor (protein) • Symptoms • Edema • Sores (skin, membranes) • Treatment/outcome • Rapidly fatal if untreated • Milk is best treatment • Long-term effects of PEM – These can be partially reversed but the effects are often long lasting 44 44 Long term effects of PEM • PEM is associated with long term disadvantage – 50% of PEM sufferers later have an IQ < 90, compared to a similar but non-PEM cohort (17%) – Apart from IQ, PEM is also associated with attention and STM problems 45 45 Pregnancy • Severe malnutrition of the mother results in spontaneous abortion (up to 4 weeks into pregnancy) • Malnutrition alone definitely: • Reduces brain weight, and number of neurons and glia – Not surprising as 250,000 neurons per minute are grown during fetal development • Has effects that are irreversible by good nutrition later in life • It has been suggested: • That raised BP, proneness to Type II diabetes and heart disease may all be consequences of poor maternal nutrition • Epigenetic basis studied in the Dutch famine cohort (1944) 46 46 Adults • Severe malnourishment in adults has a range of physiological effects – It produces impotence in men and eliminates the menstrual cycle in women – Loss of lean and fat body mass – Lowered heart rate, Basal metabolic rate & Blood pressure • Females may be able to reduce BMR further than men, which may explain their greater ability to survive famine – Edema – Lethargy and hypersensitivity to cold – Severe impairment of immune function • It is usually the latter which kills, in combination with the unsanitary conditions prevalent in such situations 47 47 Laboratory studies • The physiological and psychological effects of malnourishment were studied in a landmark US 1 year experiment • This 1940’s study aimed to find out the best way of refeeding victims of famine in war-torn Europe and the effect that refeeding would have on their physiology and behaviour • Keys had 32 conscientious objectors, volunteer for the starvation study • The initial 3 months were baseline observation followed by 6 months of a semi-starvation diet (equivalent to that of war torn Europe), followed by 3 months refeeding • Extensive physiological and psychological tests were conducted 48 48 The Keys study • The men were housed, fed and slept at the University of Minnesota for the whole length of the study • The regime: – Observation period » Average weight 70Kg (3500 Kcal) – Starvation period – Post weight 53Kg (on a 1570 Kcal diet) – They had to walk several kilometres everyday » Strength decreased 30% » Body temp dropped so that even at the height of summer they needed 3 or 4 blankets » BMR dropped 40% (saving 600Kcal) » Pulse dropped from 56 to 38 BPM and heart volume shrunk by 20% » Edema in wrists and ankles & excessive urination – Refeeding period – 1877-4158Kcal, then all at 5218Kcal – Weight regain was at the cost of lean body mass 49 49 Psychological effects • Baseline period – All willingly participated and were full and engaged participants for the first part of the study • Starvation period – Numerous psychological effects were observed, but no change in IQ or memory measures • • • • • • • • Apathy, depression, tiredness Irritability Loss of spontaneous activity Narrowing of interests Loss of libido Loss of interest in personal appearance Violence in 2 men Little interest in carrying out their routine duties 50 50 Psychological effects • A major finding (perhaps not surprisingly) was food preoccupation • • • • • • • • Thoughts and talk continuously on food Recipe and cookbook collecting Planning how they would eat the next meal All food dislikes disappeared and the monotonous diet of cereals, potatoes and turnips (28g of protein & 22g fat) got to be liked more and more Heightened possessiveness about food Meals could last up to 2 hours Extreme reactions if anyone wasted food Extensive gum chewing, nail biting and smoking – One man consumed 40 packs of gum per day 51 51 Psychological effects • A further area of study was the effect on social interaction between the men, which had initially been very positive and was described by Keys as “tolerant, happy and lively” – – – – The tone became somber, serious and the humour sarcastic All participants became highly ego-centric Social interaction became stilted and artificial The men became unable to control outbursts of temper etc, even though they were aware of their irritability • Refeeding had to be postponed by a week, which prompted a near rebellion by the participants. When it started it too had profound psychological effects – Table manners were totally abandoned – Attitudes were expressed at total odds with those reported early in the study (ego-centric) – This is clearly illustrated in Samuel Legg’s account of his experiences as a participant in this study… 52 52 Participant’s voices • Samuel Legg (pictured below before and during the study)… • “…The psychological aspects of starvation are unbelievable. We went there because we were concerned about people abroad and wanted to do what we could to help those less fortunate than ourselves, and I think we lost that feeling after about two months. At the end of 5 months of starvation our attitude was “to heck with the people abroad; I am hungry”. That was all that was important. The only important thing left was whether I was ever going to get food. I was only interested in myself…” • After 3 months of refeeding most of the psychological effects had dissipated, but further studies with other populations suggest that the psychological effects of starvation are lifelong 53 53 Long-term psychological effects • Several studies have looked at the effects of periods of starvation on peoples later behaviour towards food • This has typically focused on concentration camp survivors • One key finding has been that such survivors are far more likely to binge eat than controls who went through a similarly stressful experience • The problem here, of course, is that we can not be certain that starvation alone produced this (although some of Ancel Keys participants later behaved in the same manner) • Another interesting study interviewed holocaust survivors about their attitudes to food 54 54 Long term effects… • Many camp inmates received somewhere between 7001600 Kcal/day and some as low as 500-900 Kcal/day • The Nazi authorities (by their own admission) estimated that a healthy man could expect to live for around 3 months on this sort of diet (watery soup & bread) • Not only was this far less than in the Keys study, many had to engage in very hard labour as well as witnessing traumatic events on a daily basis • When interviewed some 50 years after the fact the survivors reported the following long term effects on their attitudes to food 55 55 Survivors report… • Extreme reactions to throwing out food • These also occur even when food is spoiled • Storing excess food (e.g., putting bread in bedside drawers) • Difficulty standing in line for food • Anxiety if food is not available in the immediate vicinity • Craving for carbohydrates 56 56 Food deprivation and longevity • So far, we have focused solely on the costs of starvation and semi-starvation, but nearly 80 years of experimental research using various animal models has suggested that some form of dietary restriction may significantly increase lifespan • We will finish this lecture by looking at this rather bizarre twist to the science of starvation 57 57 Effects of food deprivation • In 1934 McCay and Crowell demonstrated that rats fed a reduced caloric diet lived twice as long as control rats • These findings have been replicated many times in a diverse range of animals from fruit flies to mammals • Maintaining a youthful appearance • Higher activity levels • Delays in developing age-related diseases • However, semi-starvation diets do not result in extended lifespan in Rhesus monkeys (the closest test yet to trying this in humans) • Semi-starvation diets are difficult to test in humans… • Infants can not be assigned to either a calorie restricted treatment group or a normal control group! • Nonetheless a study started with older participants in 2002 indicates benefits for reduced BP • Some suggest this study is flawed as the effects of caloric restriction may only work when the animal/person is young 58 58 Why might food deprivation lengthen life-span? • Hormesis (‘excitation’) hypothesis • Low intensity biological stress may put the organism into a ‘defensive state’ which slows metabolism and ageing • Perhaps such a state could be initiated without using a starvation diet by promoting physiological factors that generate leanness? • Free radicals • Mitochondria generate more free radicals when energy is abundant • According to this theory it is free radicals which promote cell ageing • Cutting calories cuts free radicals, thus slowing ageing • Currently, how food deprivation extends life span is not understood – and similarly, we do not really know whether it will occur in humans 59 59 Conclusion • Malnourishment is a considerable problem and the cause of many preventable premature deaths • Psychologically, the effects of food deprivation share something in common with what we already know about dieting • In the next lecture we will see this relationship presented in even starker form when we examine anorexia and bulimia 60 60