BM - Diet and obesity Flashcards
Definition of obesity
“Accumulation of fat stores to an extent that compromises health.”
Why is there a high level of interest in fat as a culture?
The ‘obesity epidemic’ is a recurring theme within the media. So we might assume that the British population is more informed than ever on the topic.
What are studies on our perception of overweight?
- Study 1: Researchers at UCL carried out a study among obese adults to find out how they perceived their own weight they uncovered some surprising results .The researchers looked at data from two surveys, conducted 5 years apart in 2007 and 2012, in which 657 obese persons were asked to select a descriptor for their own body weight. They could choose from the options: very underweight, underweight, about right, overweight, very overweight, obese. The results showed that the proportion of obese adults selecting the term ‘obese’ to describe their body size was very low in both sexes: 13% of women in 2007 and 11% of women in 2012, and less than 10% of men at both time points.
Study 1: Now, of course the term ‘obese’ goes hand-in-hand with stigmatisation, which might well explain the reluctance to use it. The researchers did take this into consideration and went on to look at whether people were more likely to use the less controversial term ‘very overweight’. However, among women there was actually a decrease in the use of the term ‘very overweight’ over time. The majority of the adult obese population of Great Britain do not identify themselves as either ‘obese’ or even ‘very overweight’. - Study 2: Overweight children are at an increased risk of premature mortality and disease in adulthood.Looked at the extent to which parental and objective weight status cut-offs diverge. 2976 children in England 4-5 and 10-11 years old. A third of parents underestimate their child’s BMI. Other evidence suggests that parents who recognise their child’s weight status are more likely to perceive potential health risks. The earlier you become obese, the worse your health outcome over time.
- Study 3: 5,000 young people aged 13 to 15 who had taken part with their families in the annual health survey for England between 2005 and 2012. They had been weighed and measured and had been asked whether they thought they were “about the right weight”, “too heavy” or “too light”. Relatively few ‘normal-weight’ teens think they are too heavy, but many who are overweight do not acknowledge. 39% of overweight teenagers thought they were the right weight. Only 7% of teenagers thought they were overweight.
What is the anthropomorphic measurement of weight?
BMI
Formula: weight in kg/height in m2 Adults: - Underweight: BMI <18.5 - Normal weight: BMI = 18.5 – 24.9 - Overweight: BMI = 25 – 29.9 - Obesity: BMI =/> 30 - Severe (‘morbid’) obesity: BMI =/> 40
What are the problems with BMI?
- Famously fails to distinguish between fat and muscle- tall man at 6’2” estimated BMI over more than 30
- BMI is an unreliable indicator of actual fat- It fails to account for WHERE fat is located on the body (talk a bit more about that in a minute). There are different implications on health depending on where you are carrying the fat.
- BMI does not apply equally to people of all ethnicities- Asians have higher weight-related disease related risks- possible explanation is body fat. South Asians higher levels of body fat, and are at higher risk of weight related diseases, at lower BMI scores. Blacks have lower levers of body fat and higher lean muscle mass lower risk of obesity-related disease. International debate whether cut points for overweight and obesity should be lower cutoffs. China and Japan define overweight as a BMI of 24 or higher and obesity a BMI of 28 or higher; in India, overweight is defined as a BMI of 23 or higher, and obesity, a BMI of 27 or higher.
Weight circumference as a measurement of obesity
Central obesity is of greater risk to your health as opposed to someone who is pear shaped. Men Overweight: WC > 37 inches (94 cm) Obesity: WC > 40 inches (102 cm) Women Overweight: WC > 32 inches (80 cm) Obesity: WC > 35 inches (88 cm) Ethnic specific values for waist circumference have also been defined.
Waist to height ratio as a measurement of obesity…
- Waist should be less than half your height, so values under 0.5
- Meta-analysis of 31 studies involving of over 30,000 people in several ethnic groups, shows the superiority of WHtR over WC and BMI for detecting cardiometabolic risk factors in both sexes.
- Call for Waist-to-height ratio to be considered as a screening tool.
- Ashwell, M., Gunn, P., & Gibson, S. (2012). Waist‐to‐height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors: systematic review and meta‐analysis.Obesity reviews,13(3), 275-286.
Percentage body fat as a measurement of obesity…
- Callipers- straight forward tells you exactly to mm or inch how much fat is on your body.
- Bodystat and tanita- impedance measures. Firstly person’s height and weight and age, gender is noted. Small electrical current circulated the devices measures the impedance or resistance to the signal as it travels through the water that is found in muscle and fat. The more muscle a person has, the more water their body can hold. The greater the amount of water in a person’s body, the easier it is for the current to pass through it. The more fat, the more resistance to the current
- Hydrostatic weighing- considered a gold standard and is highly accurate- but expensive and uncomfortable. People must empty their lungs as much as possible before entering the tub and must hold their breath underwater.
- Bod Pod also expensive but also considered a gold standard. It is as accurate as hydrostatic weighing.. It can detect small changes in body fat and lean body mass (i.e., muscle, bones and organs). Utilising a technique called air displacement plethysmography the client sits comfortably in a chamber for two to three minutes whilst the volume of air displaced by the body is measured and used to calculate body fat percentage.
What are the health consequences of obesity?
Mortality and adiposity
359,387 participants from nine countries in the European Prospective Investigation into Cancer and Nutrition (EPIC) (which we will talk about more later)
Adjusted Relative Risk of Death among Men and Women in the European Prospective Investigation into Cancer and Nutrition (EPIC cohort-), according to BMI & Waist Circumference
Solid lines indicate relative risks, and dashed lines represent 95% CI
Stratification according to center and age at recruitment and additional adjustment for smoking status, educational level, alcohol consumption, physical activity, and height.
Famous J shaped associated. Risk higher in those of low and high body fat
Lowest risks of death related to BMI were observed at a BMI of 25.3 for men and 24.3 for women.
In this study both waist circumference and BMI useful for predicting death
Where can there be physical consequences of obesity?
lungs heart head liver uterus ovaries legs general body testes bowels kidney pancreas breasts throat
About obesity and cardiovascular disease…
- Leading cause of death worldwide
- Second biggest cause of death in the UK – but gender difference!
CVD group of diseases affect the circulatory system the most common of which are CHD and stroke.
CVD is the leading cause of death worldwide and the in the UK. According to the WHO it accounts for approximately 30% of worldwide deaths every year
CVD was the most common cause of death in the UK for women (28% of all female deaths), but not for men, where cancer is now the most common cause of death (32% of all male deaths).
Downward trend in CVD since the 1970s. In 2009 CVD cost the NHS £8.7 billion and the economy £19 billion.
Putting in stents has become increasingly common, having doubled in the last decade. This is part of why CVD is decreasing (but it is still the biggest killer!).
In the UK, mortality from CVD has been falling since the early 1970s->
Mortality has been declining in all regions of the UK
In England, death rates from heart attack have halved since 2002.
This decline is thought to be attributable to reductions in smoking, improved hospital treatment and better management of blood pressure and cholesterol (Smolina, Wright, Rayner, & Goldacre, 2012).
Over 92,000 percutaneous coronary interventions (PCI) were carried out in the UK in 2012, more than twice as many as a decade ago
Despite downward trends in mortality the economic costs of CVD are vast.
In 2009, the overall cost of CVD to the UK economy was an estimated £19 billion
What is the burden of diabetes?
- Increasing in prevalence globally and in the UK
- Type II diabetes: 85-95% of cases
- Undiagnosed diabetes is a problem (45% of sufferers don’t know they have it!)
- Extremely costly to health systems
T2D- chronic disease that is becoming increasing more prevalent globally.
Figure from IDF Diabetes Atlas - yearly report on worldwide trends in T2D. 382m adults worldwide (8.3% of adult population).
- Worldwide set to rise beyond 592m in next 25 years.
UK 3.2 million adults (6%) set to rise to 5 million in next 10 years (Diabetes UK)
Type II diabetes accounts for the majority of cases of diabetes and is the cause of the huge increase in prevalence in diabetes
Undiagnosed diabetes- 45% of people with diabetes are not aware that they have this serious health condition
Burden of diabetes is enormous - It is the 4th or 5th leading cause of death in most high income countries according to WHO and IDF
- Extremely costly to health systems. Accounts for almost 11% of worldwide health expenditure.
- 10% of the NHS budget
What are the complications of obesity?
- Chronic hyperglycaemia of diabetes is linked to long-term damage, dysfunction and failure of various organs.
- The harmful effects of diabetes can be divided into microvascular and macrovascular complications
- Microvascular complications (damage to small blood vessels)
• Retinopathy damage to the eyes is the biggest cause of blindness
• Nephropathy damage to the kidney can lead to kidney failure
• Neuropathy can lead to foot ulcers and is the biggest cause of amputation
The macrovascular complications encompass various cardiovascular diseases- and are the focus of my PhD but I think it is important to highlight the other deleterious side effects of this disease.
What are the microvascular consequences of obesity?
retinopathy
nephropathy
neuropathy
What are the microvascular consequences of obesity?
stroke
coronary heart disease
peripheral vascular disease
What is the relationship of obesity with cancer?
• The link between body weight and cancer is firmly established
• Meta-analysis 89 prospective studies:
• Overweight and obesity associated with increased risk of breast, colorectal, endometrial, kidney, and ovarian cancers
• Association between weight and oesophagealcancer in men only
• Mixed associations for pancreatic and prostate cancer
Guh (2009) on reading list
The link between body weight and cancer is firmly established and based on a large body of consistent evidence
• Pancreatic cancer not associated with overweight but linked with obesity
• Prostate cancer associated with overweight only
What other physical conditions are associated with obesity?
• Meta-analysis 89 prospective studies:
• Overweight and obese BMI increase the likelihood of developing asthma, gallbladder disease, osteoarthritis and chronic back pain
• For gallbladder disease WC is a better predictor of risk than BMI
• The associations get stronger as BMI increases
Gallbladder disease WC is a better predictor than BMI.
How does adipose tissue act as an endocrine organ?
Biomedical science students- I’m sure you know a lot about this but adipose tissue is an active endocrine organ
Intra-abdominal fat is key
White adipose tissue is highly complex and is composed of various cell types that interact dynamically with each other through the secretion of adipokines, including hormones, cytokines and chemokines. This tissue is now recognized as being equivalent to an endocrine organ
Abdominal fat release substances collectively known as adipokines (e.g. hormones, enzymes and cytokines) into the circulation
Adipokines associated with:
insulin resistance
dyslipidaemia [raised LDL cholesterol, triglycerides, lowered HDL cholesterol and raised blood pressure]
inflammation
About diet and Cardiovascular Disease?
• High-sodium diet increases risk of hypertension, which is a risk for CVD
• Strong evidence high consumption of trans fats causally contributes to CVD (through atherosclerosis), weaker evidence for saturated fat
• Strong evidence that vegetables, nuts & Mediterranean diet (RCT) are protective
• Moderate evidence for the protective effect of fruits, fish, whole grains, fibre and alcohol
“Evidence for most nutrients or foods too modest to be conclusive”
Dietary patterns also influence risk of coronary heart disease.
Ecological data from the Seven Countries Study showed a strong positive association (r=0.73) between saturated fatty acid intake and CHD incidence,although a much lower correlation was observed for total fat (r=0.39), suggesting that not all types of fat (ie, polyunsaturated fatty acids) are associated with an increased CHD risk.
Little direct evidence from RCTs mostly longitudinal cohort BUT RCT for Med Diet high in fv, whole grains, fish etc. and reduced CVD
About sugar and diabetes…
• “Sugar may be linked to type 2 diabetes by making a significant contribution to becoming overweight…sugar alone in your diet is not enough. Weight is determined by total energy intake”. Diabetes UK
• “The myth that sugar causes diabetes is commonly accepted…one of the biggest risk factors for type 2 diabetes is beingoverweight, and a diet high in calories from any source contributes to weight gain”. ADA
• However, sugary drinks have been linked to 30% increase risk of diabetes
– (26% adjusting for BMI!)
1. 2015 meta-analysis by Wang and colleagues, eight studies published between 2004 -2014 . A total of 286,697 participants. Majority of studies in US but also 2 in EU and 1 in Japan 2. Estimated that the risk of diabetes associated with high consumption of SSBs is 1.30 times that for low consumption. 3. Evidence from the European Prospective study in 8 European countries, showed that one sugar-sweetened soft drink daily was associated with a risk of developing diabetes 4. June 2015, the scientific journalCirculationpublished a study estimating that sugary drinks are linked to 180,000 deaths worldwide per year; of these, 133,000 were from diabetes.
About diet and cancer…
• Early research estimated 32- 35% of cancer was avoidable by diet change
• But few specific food items have been convincingly linked to cancer
• EPIC cohort (EU)
– fruit & vegetables reduce mouth, larynx, oesophagus, lung & bowel cancer risk
– BUT no effect on lymphoma, breast, prostate or ovarian cancers
• NIH-AARP study (US)
– fruit and vegetable consumption and reduced risk of head and neck cancers
– Strong link between red meat and colorectal cancer and some evidence for other cancers, including oesophagus, liver, kidney, and prostate
Research in the 80s and early 90s suggested that a third of cancers could be avoidable by changes to diet
AND we did see early that there is overall a very consistent relationship between the majority of cancers and measures of adiposity
Few specific food or drinks have been convincingly linked to cancerà diet consists of many different foods, nutrients and minerals
What was the EPID cohort?
The European Prospective Investigation into Cancer and Nutrition (EPIC) study is one of the largest cohort studies in the world, with more than half a million (521 000) participants recruited across 10 European countries and followed for almost 15 years.
EPIC was designed to investigate the relationships between diet, nutritional status, lifestyle and environmental factors, and the incidence of cancer
NIH-AARP
National Institute of Health- American Association of Retired Persons
People aged aged 50-71 years, and who resided in one of six states (California, Florida, Pennsylvania, New Jersey, North Carolina, and Louisiana) or in two metropolitan areas (Atlanta, Georgia and Detroit, Michigan). The questionnaire included a dietary section as well as some lifestyle questions. Over 500,000 people returned the questionnaire, again v large study
Positive association between red and processed meat and colorectal cancer was convincing on the basis of the results of 16 cohort studies and 71 case-control studies. Update 2011 only served to strengthen the evidence in favour of a link between red and processed meat intake and colorectal cancer
What are the emotional consequences of obesity?
Young people
• Body dissatisfaction
• Slightly lower self-esteem in community samples
• No consistent evidence of higher rates of depression in community samples
• Higher rates of depression in clinical populations
Adults
• Body dissatisfaction
• No consistent differences in self-esteem in community samples
• Higher rates of depression at the higher grades of obesity
• Higher rates of depression in clinical populations
