harmonalfactors-obesity
Obesity is a global epidemic resulting from sedentary life styles, improved socioeconomic conditions and availability of processed high caloric foods and soft drinks in industrialized societyBehavioural and dietary changes are the initial therapeutic strategies, wt loss drugs should be used with caution especially herbal preparations that combine ephedra alkaloids and caffenine, because there are serious potential adverse reactions.
Measurement of fat accumulation
• Ex or wt in relation to ht (BMI)
• Skin fold measurements
• Various body circumference particularly the ratio of waist to hip circumference.
BMI expressed in kilograms per sq meter is closely related to body fat
BMI of 25 kg/m2 is considered normal
30 kg/m2 is – obese
25 – 29.9 over weight
Other techniques for measuring body composition include under water weighing (densitometry), CAT, MRI and Dexa scanning.
CENTRAL OR VISCERAL OBESITY
Fat accumulates in trunk and in the abd cavity is associated with a much higher risk for several diseases than in excess accumulation of fat diffusely in subcutaneous tissue.
Obesity is a disorder of energy balance when food derived energy chronically exceeds expenditure the excess calories are stored as triglycerides in adipose tissue.
Three components of this system
1.The afferent system which generates humoral signals from adipose tissue (leptin) pancreas (insulin) and stomach (gherlin)
2.Central processing unit located primarily in the hypothalamus – interprets the afferent signals.
3.Effector system which carries out orders from the hypothalamic nuclei in the form of feeding behaviour.
•Gherlin is a short term mediator à increase sharply before every meal and fall promptly when the stomach is filled.
•Success of gastric bypass surgery is massively obese indiviuals may relate more to associated suppression of gherlin levels.
•Leptin has a more important role than insulin in CNS
•Adipocytes communicate with hypothalamic centers that control apeptite and energy expenditure by secreting leptin a member of cytokine family.
•Net effect of leptin therefore is to reduce food intake and promote energy expenditure.
•Hence over a period of time energy stores are reduced and wt is lost in turn reduces the circulating levels of leptin and now equilibrium reached.
•Decrease leptin levels the anabolic circuits are relieved of inhibition and catabolic circuits are not activated, resulting in net gain of weight.
GENETICS OF OBESITY
Disorder of multifactorial etiology
• BMI in monozygotic twins versus dizygotic
• Leptin – energy hemostasis – OB gene
• Leptin – melanocortin circuit – arcute nucleus of hypothalamus
Two major types of neurons that bear lepin receptors
Oraxogenic – apeptite stimulating neurotransmitters
Leptin – decrease NPY / agouti – related peptide
POMC / CART Neurons
Leptin – sensitive à POMC / CART
Anorexigenic neuropeptides alpha – melanocyte – stimulating hormone (alpha MSH) cocaine and amphetamine – related (CART)
Both are the products of POMC – catabolic effects.
NPY / AgRP and POMC / CART neurons – first order neurons.
The neurotransmitters produced by (NPY / AgRP and alpha MSH)
2nd order neurons à efferent system
0 comments: to “ harmonalfactors-obesity ”
Post a Comment