Obesity Flashcards
what is obesity? bmi?
world health organisation - undesirable weight gain caused by consuming more energy than expended
BMI over 30
leads to problems..
BUT…
like joint trauma, back pain and hypertension - Romaro-Corral
and psych problems like dep and panic disorder - Simon
negative impact on self-identity, stigmatisation (Ogden et al)
BUT some argue this is only the case when dieting (Ross) - those more educated, dieting is associated with depression at all weight levels
The heritability of adult body weight is a long-established finding
Maes
Stunkard
used a meta-analysis and reviewed over 25,000 twin studies, estimated that monozygotic twins that were raised apart from each other had a BMI heritability of 70% for males and 66% for females.
also looked at adoptees, from Denmark. Found a strong relationship found between the adoptees weight and their biological parents weight and no relationship found between the adoptees weight and their adoptive parents weight.
Price
completed a study investigating the body fat of monozygotic twins raised apart and raised together. They found that the body fat of monozygotic twins raised together correlated at 0.75 compared to MZ twins raised apart which correlated at 0.66. Although the correlation for that of monozygotic twins raised apart was less it is important to note the correlation was still fairly high and this can suggest that being raised separately had little effect on heritability.
Genetic malfunction- name, author and what is causes
Prader-Willi Syndrome is the most common form of obesity that is caused by a genetic syndrome. Individuals will Prader-Willi have a loss of a particular gene in chromosome 15 (Holm, 1993) which results in the individual suffering from a range of health and bodily issues, one being hyperphagia. Hyperphagia is the feeling of constantly needing to eat as the individual never feels full.
BUT.. statistics of obsesity v genetic disorder
1 in 20 adults are obese (NHS UK, 2016) whereas Pradar-Willi affect 1 in 10,000.
various gene distruptions have been identified
O’Rahilly
most of the identified mutations position..
the leptin/melanocortin (leptin tells the body when to stop eating) pathway in the central nervous system (CNS) as critical in the regulation of whole-body energy homeostasis (Coll et al
Wardle, Carnell and Haworth
Investigated the association between alleles of FTO known to increase obesity risk and measures of habitual appetitive behaviour
=The intronic FTO single nucleotide polymorphism genotyped in 3337 TEDS
=measures of habitual appetitive behavior two scales from the Child Eating Behaviour Questionnaire (CEBQ)- (Satiety Responsiveness and Enjoyment of Food),
= the A allele was associated with increased adiposity in this cohort
= AA homozygotes had significantly reduced Satiety Responsiveness scores
= Mediation analysis indicated that the association of the AA genotype with increased adiposity was explained in part through effects on Satiety Responsiveness.
=the commonest known risk allele for obesity is likely to exert at least some of its effects by influencing appetite
Eating/appetitive traits
Carnell et al - In order to directly assess generalised eating traits (rather than infer them from observed behaviour), we have used the Child Eating Behaviour Questionnaire (CEBQ), this is a parent-report instrument developed to assess eating behaviour traits in children. Parents of 8–11 year old twins from TEDS, completed the CEBQ Satiety Responsiveness and Enjoyment of Food scales. It was found that with both indices of adiposity (BMI z score, waist z score), adiposity was negatively associated with satiety responsiveness and positively associated with enjoyment of food. These results strongly suggest appetitive traits are associated with adiposity throughout the weight distribution.
This study is good because it uses waist score and BMI - women tend to store more fat subcutaneously rather than in visceral adipose tissue, so at the same BMI, women will tend to carry more body fat than men (Ogden et al). Therefore to account for these differences in fat distribution, waist-to-hip ratio (WHR) is commonly used and BMI and WHR are correlated.
