Obesity is as eveyone knows a real and threatening modern problem. The simple minded think that obesity is a result of eating too much. That the ready provision of food in the West just means that people eat to much in relation to their activity. There are very few fat people in the poor areas of Asia and Africa.
For many this is too simplistic an explanation.
For my part I often wonder if the epidemic amongst Western populations is a result of more food being available to populations whose ancestors had for many generations adjusted to being starved or barely fed. And then in relatively recent times they have ready access to food, catch up time. Their bodies are accustomed to starvation and are overwhelmed by the available food and become fat. Genetic constitution is also a factor, maybe the epidemics and starvation of the past has selected a population more prone to obesity once food is plentiful.. The hormone leptin appears to have a role in calorie intake control. Lower blood leptin concentrations and food intake leaps.
It is also interesting that fat distribution is different between men and women, round the hips in women and the uppper abdomen in men.
What is clear is that the health and physical well being of obese men, women ansd children is compromised.
A recent interesting finding is that the intestinal flora of obese humans and mice differ from those of lean individuals. The two predominant populations of microbacteria in the gut are members of the Firmicutes and Bacteroidetes families. Obese mice have higher proportions of Firmicutes which have enzymes which are efficient in digesting normally indigestible polysaccharides. ( Nature 2006, vol 444, pp1009-10; 1022-1023; 1027-1031
What is not clear is if this is a cause or effect. A person who over eats will have the possibility of more food passing unabsorbed into the colon feeding the bacterial population there.
Under pressure over obesity the food industry is beginning to look for ideas to alleviate the problem. For example the drug firm Phytopharm is studying a plant called Hoodia, which grows close to the Orange River by the Kalahari Desert which it is said depresses appetite. This idea is being extended by Unilever.
Despite the explosion of information that we now have on obesity , this
epidemic continues to increase in severity.
In the Nutrition Society Sir David Cuthbertson Medal Lecture Gemma Fruhbeck reviews the contemporary view of this problem
Proceedings of the Nutrition Society 2006, 65, 329-347
Understanding the neuroendocrine systems that regulate energy homeostasis, and adiposity has been a long-standing challenge in studying obesity, which is an increasingly important public health problem. Adipose tissue is no longer considered to have no role in body-weight regulation. It actively secretes a large number of hormones, growth factors, enzymes. cytokines. complement factors and matrix proteins, at the same time as expressing receptors for most the
control of fuel storage, mobilisation and utilisation at both central and peripheral sites. Thus, an extensive interaction at a local and systemic level in response to specific external stimuli or metabolic changes underpins the multifunctional characteristics of adipose tissue. In addition to the already-known adipokines, such as IL, TNFα, leptin, resistin and adiponectin,, there are newly identified factors concerned in adipose tissue metabolism; aquaporin, caveolin, visfatin. serum amyloid A and vascular endothelial growth factor. Genomics. proteomics and metabolomics are identifying new insights into the molecular basis of obesity.
H. David McCarthy ( Proceedings Nutrition Society 2006, 65, 385-392) discusses the important point of measurements in children as predictors for the metabolic syndrome: focus on waist circumference. Rather than excess general fatness (assessed by BM1). more specifically it is excess abdominal fatness, waist circumference measurement, which is a better measure . Abdominal fat measurements in children is proving to be more clinically useful. Waist circumference centile charts have now been developed for the UK and other paediatric populations to assist in this process. Abdominal fatness has increased in infants, children and adolescents to a greater extent than overall fatness over the past 10-20 years, suggesting that obesity prevalence may be underestimated when based entirely on BMI. Additionally, ethnic differences in fat distribution have been demonstrated in children, with those from south Asian backgrounds having a greater abdominal distribution .
Rennie KL et al have written a review on The effect of physical activity on body fatness in children and adolescents ( Proceedings Nutrition Society, 2006, 65, 393-402) and discuss the lack of consistency between studies that have investigated the relationships between measurements of physical activity and energy expenditure and body fatness in children. This may be because energy intake is more important . Or that the methodology for measuring activity and body composition. does not adjust physical activity energy expenditure and differences in body composition, or body fat is not appropriately adjusted for body size. It may be more important to measure the amount and intensity of physical activity required to prevent fat-mass gain than the energy expended in physical activity. A clearer understanding of the psycho-social, behavioural and environmental factors that influence activity is needed, including the interactions between physical activity and other behaviours such as time spent sedentary, sleeping and eating.
Having said that I just wonder if the whole problem is basically one of eating too much.. Food is so cheap and plentiful and there is a massive industry dependent upon sales. The metabolic responses are fascinating. The cause may be simple, gluttony
- Martin Eastwood