Posts Tagged ‘fat cells’

Downey Fact Sheet 1 – About Obesity

September 27th, 2009

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Obesity is a global epidemic and a major health concern because of its premature mortality and extensive comorbidities. Obesity is a common, complex, multifactorial disease with a high degree of heritability. Between 25 and 40% of person with obesity have a parent who is obese. There are several significant facts to bear in mind when discussing obesity:

By Julie Snider for the Downey Obesity Report

By Julie Snider for the Downey Obesity Report

Every individual inherits a certain number of fat cells or adipose tissue. Obesity requires (a) a large number of fat cells or (b) a large volume in each fat cell or (c) both. Adipose tissue continues throughout the lifespan. Weight loss, including surgically-induced weight loss, does not remove fat cells. This is why weight regain is so common. Individuals with obesity have significantly more fat cells than the non-obese, 23-65 billion compared to 37-237 billion for persons with obesity . Early onset obesity is associated with increase adipose cell number while adult obesity is associated with normal cell number. There are two phases of life in which growth of adipose cells are likely to develop: very early, within the first few years of life and between the ages of 9-13 years of age. Those who become very obese early in life are the ones who have nearly normal cell size but have the greatest increase in cell number; whereas those with onset of obesity between 9-13 have more change in cell size than cell number. Salans LB, Cushman SW, Weisman RE, Studies of human adipose tissue. Adipose cell size and number in non0bese and obese patients. J. Clin Invest. 1973 Apr’ 52(4): 929-41)

Extremely obese individuals may have four times the number of fat cells as lean counterparts. http://www.jpp.krakow.pl/journal/archive/1205_s6/pdf/5_1205_s6_article.pdf

Human food intake and energy expenditure are controlled by complex, redundant and distributed neural systems that reflect fundamental biological reaction to food supply and energy balance. The hypothalamus and caudal brainstem play a critical role. The limbic system is important for processing information regarding previous experience with food, reward and emotion. The predisposition to store considerable amounts of energy as fat for later use is now a major health risk. Brain, appetite and obesity – PubMed Results

Extensive research over the past 10 years has shown that appetite is regulated by a complex system of central and peripheral signals which interact in order to modulate the individual response to nutrient ingestion. Satiety signals include cholecystokinin, glucagon-like peptide and peptide YY which originate from the gastrointestinal tract during a meal and through the vagus nerve reach the caudal brainstem. Here the signals move to the arcuate nucleus where satiety signals are integrated with adiposity signals, namely leptin and insulin, and with several other inputs create a neural circuit which controls the individual’s response to a meal, i.e. keep eating or stop. Neuro-hormonal control of food intake: basic mecha…[J Physiol Pharmacol. 2005] – PubMed Result

Adipose tissue, rather than some inert, jello-like, substance is an active hormonal tissue, secreting many hormones which are involved in creating signals from the gut to the brain, indicating hunger or satiety. These hormones include insulin, leptin, ghrelin, PYY-33-6, adiponctin, resistin and visfatin as well as cytokines and chemokines, such as tumor necrosis factor-alpha, interleukin-6 and others. These can lead to a chronic sub-inflammatory state which plays a critical role in the development of insulin resistance, type 2 diabetes, increased risk of cardiovascular disease associated with obesity. Adipokines: the missing link between insulin resis…[Diabetes Metab. 2008] – PubMed Result

Understanding Obesity

September 26th, 2009

While body weight is made up of several components – bone, muscle, etc. when we talk about obesity we are referring to excess fat tissue, also called adipose tissue. There are two kinds of fat tissue, brown and white (like rice come to think of it). Brown tissue is mainly found in newborn babies which serves to protect babies by releasing heat. It is converted into white cells in adults. (Scientists are looking at whether white can be converted back into brown tissue and burnt off.) White adipose tissue is made up of cells called adipocytes. These contain fat made of triglycerides and other compounds. White fat cells secrete resistin, adiponectin and leptin. The average adult has 30 billion fat cells weighting about 30 pounds. Fat cells can increase in size about 4 fold before dividing and increasing the total number of fat cells present. Adipocytes also secrete estrogen which probably accounts for higher rates of some cancers in obese persons. Adipose tissue also secrete cytokines. Among the most interesting cytokines identified has been leptin, a molecule considered to send signals to the brain of satiety, i.e. the signal to the brain to stop eating.