Understanding Nutrition Chapter 9 Weight Control: Overweight and Underweight By A. Fellah, Ph.D.
A Fat Cell Excess energy is stored in the fat cells of adipose tissue. The amount of fat reflects both the number and the size of fat cells
accommodate its swollen contents. An Adipose Cell An adipose, or fat, cell seems to expand almost indefinitely. The more fat it stores, the larger it grows.
Fat Cell Metabolism • Lipoprotein lipase (LPL) promotes fat storage in both adipose and muscle cells. • LPL is mounted on fat cell membranes. • Obese people have many fat cells, they have more LPL activities in their fat cells than lean people do. • LPL activities is partially regulated by gender-specific hormones-estrogen and testosterone. • Lower body is less active than the upper body in releasing fat. • Easily regain lost weight: LPL activity increases after weight lose (the fatter the fastest).
Fat Cell Development Fat cells are capable of increasing their size by 20-fold and their number by several thousandfold.
Causes of Obesity • Set Point: The point at which controls are set. The set-point theory that relates to body weight proposes that the body tends to maintain a certain weight by means of its own internal controls. 1. Genetics: • Identical twins are 2x as likely to weigh the same as fraternal twins. • Genes may not cause obesity, but genetic factors may influence the food intake and activity patterns and the metabolic pathways. • Liptin: a protein produced by fat cells under direction of the ob gene that decreases appetite and increases energy expenditure. • ob is the obesity gene that expressed in the fat cells which codes for liptin. • It acts as a hormone, in the hypothalamus. • Mice with a defective ob gene don’t produce leptin and can weigh up to 3x as normal mice and have 5x as much body fat.
Leptin’s Action in the Body When leptin levels are high, the hypothalamus produces melanocortins, dampen appetite Leptin maintains energy homeostasis. When the body gains fat, the increase in leptin shifts energy balance toward the negative: eat less and spend more energy. Such a scenario would ensure that all fat gains were followed by losses, but this is not the case in reality, of course.
Leptin’s Action in the Body When the body loses fat, the decrease in leptin shifts energy balance toward the positive: eat more and spend less energy.
Most obese people have high levels of leptin, but their energy balance does not automatically shift to the negative, suggesting a resistance to leptin’s action in obesity. When leptin is low, hypothalamus produces neuropeptide Y, which stimulates appetite and slows energy expenditure (Leptin inhibits neuropeptide Y production) When leptin level is high, the hypothalamus produces melanocortins, which dampen appetite and increases energy expenditure.
Both mice are genetically Obese, they lack the gene for Leptin Receives Leptin No Leptin
Mice with and Without Leptin Compared Both of these mice have a defective ob gene. Consequently, they do not produce leptin. They both became obese, but the one on the right received daily injections of leptin, which suppressed food intake and increased energy expenditure, resulting in weight loss.
Causes of Obesity, cont. 2. Environment: • Overeating: • Overweight people overeat, whether this is true has been difficult to determine. • Genetically obese rats eat much more than their nonobese littermate at early age. • Overeating contributes to obesity, but does not fully explain it. • Toxic food environment: a term coined to refer to the easy access to and overabundance of high-fat, high kcalories food in our society.
Physical Inactivity: Modern technology has replaced physical activity at home and at work. Remote control, escalators, automobiles, buttons, …….. Inactivity contributes to weight gain and poor health. Watching TV may contribute most to physical inactivity. People may be obese, not because they eat too much, but because they move too little.
Pear Shaped Body Basic body shapes. The pear normally has narrow shoulders, a small chest, and an average-size waist. Fat is concentrated in the hips and thighs. Weight loss in these areas is usually difficult.
Pear Shaped Body The apple looks round in the middle. Fat is concentrated in the waist and can be lost with diet and exercise. Apple-shaped people are at increased risk for diabetes, hypertension, high blood cholesterol, and heart disease.
Body Fat Location Is Important to Health: Apple The man on the left is 6 feet tall and weighs 240 pounds; the man on the right is 6 feet 1 inch tall and weighs 230 pounds. Although similar in weight and height, the man on the left is at higher risk for diabetes, hypertension, and heart disease due to his “apple” shape and body fat content.
Controversies in Obesity Treatment • Elusive Goals: • Every overweight person can achieve slenderness and should pursue it. • Only 5% of all people who successfully lose weight maintain their losses for at least a year.
Dangers of Weight Loss: Fad Diets: often sound good, but fall short to delivering on their promises. Adverse reactions from headache to death. Weight Cycling: repeated cycles of weight loss and gain, yo-yo effect. Increase the risks of chronic disease and premature death. Psychological Problems: Most weight-loss programs assume that the problem can be solved simply by applying willpower and hard work. Ineffective treatment and its associated sense of failure add to a person’s psychological burden.
The Weight Cycling Effect of Repeated Dieting Each round of dieting is followed by a rebound of weight to a higher level than before.
Obesity in Adults Prevalence of overweight among adults in the United States
Gradual Weight Loss Increases Success People who lose weight gradually are more likely to keep it off than those who lose weight rapidly. The weight loss graphed here averages a quarter pound per week.
The Psychology of Weight Cycling Shows how the devastating psychological effects of obesity and dieting perpetuate themselves.
Aggressive Treatments of Obesity 1. Drugs: • An effective drug that can used over time without adverse side effects currently doesn’t exists. • Sibutramine: suppresses appetite by inhibiting the uptake of serotonin in the brain, suppressing appetite. • Effective when used with a reduced-kcalorie diet and physical activity. • Dry mouth, headache, constipation, insomnia, and high blood pressure. • Orlistat: Inhibits pancreatic lipase activity, thus block fat digestion and absorption by 30%. • Effective with a reduced-kcalorie diet, low fat diet. • Gas, frequent bowel movement and reduced absorption of fat soluble vitamins.
Diet Aids • Herbal Products: • St. John’s wort: contains substance that enhance serotonin which suppress appetite.
Weight Loss Drugs There is no lack of weight-loss books and products. There is a lack of approaches that help people keep weight off.
Weight-Loss Products A few examples of bogus weight-loss products that were removed from the market.
Weight-Loss Products: Herbal A few examples of bogus weight-loss products that were removed from the market.
2. Surgical Procedures Used in Treatment of Obesity The dark pink areas highlight the flow of food through the GI tract. Notice that the procedure maintains a relatively normal flow. The pale pink areas indicate the sections that have been bypassed.
Surgical Procedures Used in Treatment of Obesity The dark pink areas highlight the flow of food through the GI tract. Notice that the flow bypasses most of the stomach, all of the duodenum, and some of the jejunum. The pale pink areas indicate the sections that have been bypassed.
Weight Goals and Expectations Compared Reasonable weight goals and expectations compared.
Reasonable Treatments of Obesity • Eating Plans: • Be involved in planning. • “Energy out” should exceed “energy in” by about 500 kcal/day. • Make nutritional adequacy a high priority. • Emphasize nutrient-dense foods. • Eat small portions. Share a restaurant meal with a friend or take home half for lunch tomorrow. • Limit low-fat treats to the serving size on the label. • Make legumes, whole grains, vegetables, and fruits central to your diet plan. • Eat slowly. • Limit high-fat foods. • Limit concentrated sweets and alcoholic beverages. • Drink a glass of water before you begin to eat and another while you eat. Drink plenty of water throughout the day (8 glasses or more a day).
Reasonable Treatments of Obesity, cont. • Physical Activity: • Activity and Energy Expenditure. • Activity and Basal Metabolism. • Activity and Appetite Control. • Activity and Psychological Benefits. • Choosing Activities. • Spot Reducing.
Reasonable Treatments of Obesity, cont. • Behavior and Attitude: • Behavior modification: the changing of behavior by the manipulation of antecedents (cues or environmental factors that trigger behavior), the behavior itself, and consequences (the penalties or rewards attached to behavior). • Behaviors change tip: • Keep a record of diet and exercise habits; it reveals problem areas. • Strategies: Don’t grocery shop when hungry. Eat slowly. Exercise when watching TV. • Learn alternative way to deal with emotions and stress. • Attend support groups regularly or develop supportive relationships with others. • Adopt permanent lifestyle changes to achieve and maintain a health weight.
Reasonable Treatments of Obesity, cont. • To prevent excessive weight gain: • Eat regular meal and limit snacking. • Drink water instead of high-kcalorie beverages. • Select low-fat foods regularly and limit dietary fat to 30% of daily kcalorie intake. • Become physically active and limit TV viewing time. • Underweight: • It is a body weight so low as to have adverse health effects; it is generally defined as BMI <18.5. • It is a far less prevalent problem than overweight, affecting ~ 5% of US adults. • Thin people may find gaining wt difficult. • In wt gain or wt loss, physical activity and energy intake are essential components to a sound plan.
Weight-Gain Strategies • Eat energy-Dense Foods. • Eat at least 3 meals a day. • Eat large potions of food and expect to feel full. • Eat snacks between meals. • Drink plenty of juice and milk. • Exercise and eat to build muscles.
Eating Disorder Terms • Anorexia Nervosa • Binge-eating disorder • Bulimia Nervosa • Cathartic • Cognitive therapy • Eating disorder • Emetic • Female athlete triad
Eating Disorders in Women Eating disorders occur in males as well as females, but females make up approximately 95% of all cases.
Anorexia Nervosa A day’s diet? For a person with anorexia nervosa, it was. The foods shown provide approximately 562 calories.
Essential Features Helping to Diagnose Criteria used for the diagnosis of anorexia nervosa.
Women with anorexia nervosa see themselves as fat even when they are dangerously thin.