Weight Management Overweight and Underweight Copyright 2005 Wadsworth Group, a division of Thomson Learning

Increasing prevalence of obesity (BMI of 30 or greater) among U.S. adults

Fat Cell Development Copyright 2005 Wadsworth Group, a division of Thomson Learning The maximum growth of the number of fat cells happens during childhood and adolescence Children who are obese have a lot more fat cells than children who are not Existing fat cells store fat easily so people with more fat cells tend to regain fat more easily Remember fat cells are capable of increase in size as well as in number even in adults

Fat Cell Metabolism Lipoprotein lipase (LPL) –LPL promotes fat storage both in the fat cells and muscle cells –People with more fat cells produce more LPL in their fat cells (but not muscle cells) making fat storage more likely –Gender differences (Estrogen vs Testosterone) –In women, more LPL is be produced by fat cell from the breasts, hips and thighs and the fat cells from these parts of the body do not release their fat easily –In men, more LPL is produced by fat cells in the abdomen leading to central obesity

Fat Cell Metabolism Lipoprotein lipase (LPL) (contd) –LPL activity goes up after weight loss and it goes up more in people who were fattest prior to weight loss Set-point theory (can we really change our weight?) –The role of the enzymes involved in fat accumulation and release as well as other systems in the body that control variables such as blood glucose etc are considered the basis of the set-point theory –Proposes that the body tends to maintain a certain weight by its internal mechanisms –This is given as one of the reasons why some people’s weight or fat levels don’t change –It has been shown that after weight gains or losses, the body tends to change its metabolism to revert back to the original weight

Fat Cell Metabolism Hyperplastic obesity –Increase in number of fat cells Hypertrophic obesity –Increase in the size of fat cells Lipotoxicity – Excess lipid accumulation in non-adipose tissues is associated with insulin resistance (body does not respond well to insulin) and heart failure –Such adverse effects of fat accumulation in non- adipose (non-fat cell) tissues is called lipotoxicity Copyright 2005 Wadsworth Group, a division of Thomson Learning

Causes of Obesity Genetics –Leptin Hormone Act primarily in the hypothalamus Suppresses appetite and increases energy expenditure Leptin given intravenously to mice with a mutation in the leptin gene made them lose weight Most humans do not have this mutation However some individuals may have a defect in the system that recognizes leptin –Ghrelin –PYY Copyright 2005 Wadsworth Group, a division of Thomson Learning

Causes of Obesity Genetics –Ghrelin Hormone secreted by stomach cells Acts on the hypothalamus Triggers desire to eat But strangely, lean people have high ghrelin levels than obese people It is extremely high in anorexia patients It is involved in more complex functions than just hunger –PYY Another protein interrelated with ghrelin function Decreased food intake The amount of PYY secreted depends on the number of calories ingested May potentially be a treatment for obesity Copyright 2005 Wadsworth Group, a division of Thomson Learning

Causes of Obesity Genetics –Uncoupling proteins White body fat –Stores fat for other cells to use Brown body fat –Releases stored energy as heat –Energy is released is uncoupled from ATP formation –Useful for keeping warm –Still being studied Copyright 2005 Wadsworth Group, a division of Thomson Learning

Causes of Obesity Environment –Gene pool The collection of genes in the world hasn’t changed but obesity is increasing so the environment must have a big influence –Overeating Abundance –Physical inactivity Conveniences –We don’t use energy –The non-energy using activities fill up the time that would have been taken by energy using activities Copyright 2005 Wadsworth Group, a division of Thomson Learning

Health Risks Overweight in good health Obese or overweight with risk factors Obese or overweight with life- threatening-condition Copyright 2005 Wadsworth Group, a division of Thomson Learning

Perceptions And Prejudices Social consequences Psychological problems Copyright 2005 Wadsworth Group, a division of Thomson Learning

The Psychology of Weight Cycling

Dangerous Interventions Fad diets Over-the-counter drugs –Benzocaine –Phenylpropanolamine –Ephedrine or Ephedra (amphetamine- like) Copyright 2005 Wadsworth Group, a division of Thomson Learning

Dangerous Interventions Herbal products and dietary supplements –St. John’s wort Serotonin Copyright 2005 Wadsworth Group, a division of Thomson Learning

Dangerous Interventions Other gimmicks –Cellulite Copyright 2005 Wadsworth Group, a division of Thomson Learning

Aggressive Treatments Of Obesity Clinically severe obesity Drugs –Sibutramine Suppresses appetite –Orlistat Inhibits pancreatic lipase Copyright 2005 Wadsworth Group, a division of Thomson Learning

Surgical Procedures Copyright 2005 Wadsworth Group, a division of Thomson Learning