Obesity
Obesity is essentially an excessive accumulation of triacylglycerols in fatty tissue that is the net result of excessive energy intake compared to energy usage.Accumulation of fat, or triacylglycerol, is essentially the only way that body weight can become excessive, as other energy stor(e.g.carbohydrate glycogen or protein in liver and muscle) does not have the potential of adipose tissue to exceed the limits of requirement.
ASSESSMENT OF OBESITY by THE BODY MASS INDEX (BMI)
BMI Is defined as body mass (in kg) divided by the square of the height (in metres) (weight in kg) / height in meters)2
Classification of body weight according to BMI
ClassificationPrincipal cut-off pointsUnderweight<18.50Normal range18.50 - 24.99Overweight≥25.00Obese
≥30.00Causes of obesity
Essentially obesity results from an imbalance between calorie intake and expenditure and the main causes of obesity are Many factors contribute towards obesity. Some of the most prominent factors are assorted below:1-Genetics
2-Diet high in carbohydrates and Overeating3-Lack of physical exercises
4-Psychological factors
5- Medical reasons In some patient who develops obesity, the following: ENDOCRINE FACTORS INFLUENCING OBESITY
1. Cortisol is a well-described enhancer of fat deposition as in Cushings syndrome
2. Hypothalamic damage ( due to trauma, post-meningitis, tumor)
3. Hypothyroidism
4. Polycystic ovarian syndrome (PCOS)
Adepoce cell secret hormones
There is recent evidence showing that. rather than simply a passive fuel store, adipose tissue is an active endocrine organ, secreting peptide hormones which included
1- HYPERLINK "http://en.wikipedia.org/wiki/Leptin" \o "Leptin" Leptin is an adipocyte-derived hormone that acts to reduce food intake and increase energy expenditure . Leptin acts within the CNS to inhibit food intake and increase energy expenditure
2-Adiponectin Adiponectin is an adipocyte-secreted protein that circulates in high concentrations in the serum and acts to increase insulin sensitivity.
3- Resistin is another hormone secreted by adipocytes and acts on skeletal muscle myocytes, hepatocytes and adipocytes.
Opposite in directional effects to adiponectin, higher resistin may decrease insulin sensitivity
CONTROL OF APETITE
The appetite centre located in hypothalamus, where various influences are integrated to regulate food intake. These include central (brain-derived) signals, such as:
1. Neuropeptide-Y (NPY)
2. Melanocyte stimulating hormone (MSH)
3. Cocaine and amphetamine-related transcript (CART)
. as well as peripheral (body-derived) signals, including:
1. Leptin (ex-adipose tissue)
2. Insulin (ex-β-cells)
3. Cholecystokinin (CCK) (ex-small bowel)
4. Ghrelin (ex-stomach)
Signal regulation of appetite
A. Long-term signals.
1. Leptin:
(Greek Leptos, "thin") is is a HYPERLINK "https://en.wikipedia.org/wiki/Hormone" \o "Hormone" hormone made by HYPERLINK "https://en.wikipedia.org/wiki/Adipose_cells" \o "Adipose cells" adipose cells that helps to regulate HYPERLINK "https://en.wikipedia.org/wiki/Energy_homeostasis" \o "Energy homeostasis" energy balance by inhibiting on reaching the brain, acts on receptors in the hypothalamus to curtail appetite Leptin the "satiety. Leptin is opposed by the actions of the hormone HYPERLINK "https://en.wikipedia.org/wiki/Ghrelin" \o "Ghrelin" ghrelin, the "hunger hormone". Both hormones act on receptors in the HYPERLINK "https://en.wikipedia.org/wiki/Arcuate_nucleus" \o "Arcuate nucleus" arcuate nucleus of the HYPERLINK "https://en.wikipedia.org/wiki/Hypothalamus" \o "Hypothalamus" hypothalamus to regulate appetite to achieve HYPERLINK "https://en.wikipedia.org/wiki/Energy_homeostasis" \o "Energy homeostasis" energy homeostasis. In obesity, a decreased sensitivity to leptin occurs, resulting in an inability to detect satiety despite high energy stores
Leptin acts on receptors in the lateral hypothalamus to inhibit hunger and the medial hypothalamus to stimulate satiety
In the lateral hypothalamus, leptin inhibits hunger by
counteracting the effects of HYPERLINK "https://en.wikipedia.org/wiki/Neuropeptide_Y" \o "Neuropeptide Y" neuropeptide Y, a potent hunger promoter secreted by cells in the gut and in the hypothalamus
In the medial hypothalamus, leptin stimulates satiety by
promoting the synthesis of α-MSH, a hunger suppressant
so net action of Leptin inhibits neuropeptide Y (NPY) and activates α-melanocyte-stimulating hormone (α-MSH).
Obesity has serious long-term medical complications which include:
Type 2 /Non-insulin-dependent diabetes
Hypertension
Hyperlipidaemia & coronary heart disease
Osteoarthritis of weight-bearing joints
Cancer (esp endometrium, breast, colon)
Earlier onset of puberty
HOW DOES OBESITY CAUSE INSULIN RESISTANCE AND GLUCOSE INTOLERANCE?
1. In obesity, abundance of circulating fatty acids and liver-derived triglyceride (VLDL) provide an excellent fuel for muscle, decreasing their requirement for glucose
2. Exercise stimulates glucose transport into skeletal muscle (via induction of the glucose transporter GLUT-4). Obese subject tend to be sedentary, and thus muscle consumes less glucose
3. Increased delivery of fatty acids to liver (as in visceral obesity) enhances gluconeogenesis i.e. hepatic glucose output. In lean individuals, this only happens in during starvation, where it is appropriate.
4. Increased FFAs cause insulin resistance directly by activating enzymes that decrease the response to insulin, thereby aggravating the pre-existing insulin resistance
Reduce the obesity by
At the individual level, people can:limit energy intake from total fats and sugars;
increase consumption of fruit and vegetables, as well as legumes, whole grains and nuts;
engage in regular physical activity (60 minutes a day for children and 150 minutes per week for adults).
Individual responsibility can only have its full effect where people have access to a healthy lifestyle. Therefore, at the societal level it is important to:
support individuals in following the recommendations above, through sustained political commitment and the collaboration of many public and private stakeholders;
make regular physical activity and healthier dietary choices available, affordable and easily accessible to all - especially the poorest individuals.
The food industry can play a significant role in promoting healthy diets by:
reducing the fat, sugar and salt content of processed foods;
ensuring that healthy and nutritious choices are available and affordable to all consumers;
practicing responsible marketing especially those aimed at children and teenagers;
ensuring the availability of healthy food choices and supporting regular physical
activity practice in the workplace.
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