* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Obesity and Energy Balance
Thrifty gene hypothesis wikipedia , lookup
Overeaters Anonymous wikipedia , lookup
Hunger in the United States wikipedia , lookup
Ketogenic diet wikipedia , lookup
Selfish brain theory wikipedia , lookup
Saturated fat and cardiovascular disease wikipedia , lookup
Adipose tissue wikipedia , lookup
Vegetarianism wikipedia , lookup
Raw feeding wikipedia , lookup
Fat acceptance movement wikipedia , lookup
Cigarette smoking for weight loss wikipedia , lookup
Gastric bypass surgery wikipedia , lookup
Food choice wikipedia , lookup
Human nutrition wikipedia , lookup
Abdominal obesity wikipedia , lookup
Obesity and the environment wikipedia , lookup
Calorie restriction wikipedia , lookup
Low-carbohydrate diet wikipedia , lookup
Diet-induced obesity model wikipedia , lookup
Advanced Healing Methods GCU Holistic Health Fall 2009 Obesity Surgeon General: “Overweight and obesity result from excess calorie consumption and/or inadequate physical activity.” US, 1970’s to 1990’s: increased caloric intake NHANES- 1971 to 2000- 150 calories per day in men, 350 in women USDA- 1971 to 1982: 3300 calories per day per person 1993-1997: 3800 calories 90% of the 500 calories from carbs The rise in obesity also coincides with increasing exercise The Pima Indians Highest rates of obesity and diabetes in the US NIH: “As the typical American diet became more available on the reservation after the war (WW II), people became more overweight.” “If the Pima Indians could return to some of their traditions, including a high degree of physical activity and a diet with less fat and more starch, we might be able to reduce the rate, and surely the severity, of unhealthy weight in most of the population.” The Pima Indians Early 19th century and before Game, fish, clams, corn, beans, cattle, poultry, wheat, melons, figs, cactus 1846: “Sprightly… in fine health… the greatest abundance of food” 1860’s: “Years of famine” as white and Mexican settlers came in Game hunted nearly to extinction, water taken by the whites 1890’s: government rations to avoid starvation 1900’s: “Real obesity is found almost exclusively among the Indians on reservations” The rations- 50% of calories from sugar and flour 1950’s: “large quantities of refined flour, sugar, and canned fruits high in sugar,” also soda, candy, chips, cakes 1962: “soda pop is used in immense amounts” Energy Balance First Law of Thermodynamics A calorie is a calorie, calories in = calories out Change in energy stores = energy intake – expenditure Weight gain accompanied by positive energy balance But not necessarily caused by it Two possibilities Overeating and inactivity cause obesity “Willful descent into self-gratification” The obese responsible for their condition Character defect- they overeat and won’t change Willpower is the cure Like alcoholism from overdrinking Metabolic imbalance induces overeating and inactivity, resulting in obesity Energy Balance Diseases of civilization associated with obesity 2 hypotheses Obesity causes or worsens the conditions of metabolic syndrome and the diseases of civilization And obesity caused by overeating, particularly a high-fat diet, and inactivity, so low-fat diet to fix The same metabolic imbalance that drives us to fatten also causes metabolic syndrome and the diseases of civilization Hormonal (metabolic) effects on weight Positive caloric balance in children Eating because they’re growing- hormone-driven Weight gain in pregnancy hormonal Height genetic and driven by hormones All of these induce a positive caloric balance The Low-Fat Diet Low-fat, high-carb diets recommended for weight loss Fats fatten us the most effectively (in this view) Evidence Association between CVD, DM, and obesity If high-fat diets cause CVD, and if CVD, DM, and obesity move together in populations, then the high-fat diet causes all three But there is no strong evidence for this! Rats become obese on a high-fat diet But only susceptible strains- others don’t And even these will grow fatter on high-fat, high-carb than on high-fat, low-carb And rats will also fatten when fed sugar As will other animals, like pigs (who digest most like humans) Rats get obese on unlimited grocery food But they choose the high-carb food, not the high-fat, low-carb food The Low-Fat Diet Low-fat, high-carb diets recommended for weight loss Evidence The density of fat cals fools people into eating too many Fats have 9 calories/gram, while carbs (and proteins) have 4 apiece So eating the same amount of food as fat rather than carbs results in increased calorie intake Theory- we match intake to output by simple mechanisms like limiting the volume of food intake So fiber-rich veggies fill our stomachs with indigestible cals But- rat diets diluted with water, fiber, and clay Rats keep eating until they get their usual caloric intake 90% of daily cals put into stomachs, and they stop eating But not when water put in Rats adjusting intake in response to calories, not volume, mass, or taste So- obesity as a defect of behavior ? Hunger and satiety dissociated from underlying metabolism That hunger might be a communication from the body about underlying conditions is rarely considered Studies Low-cal semi-starvation diets “Balanced” diets with fewer calories Benedict 1917 2 groups of 12 men, 1400-2100 calories per day, 3 mos Weight loss Constant hunger, feeling cold Metabolism slowed 30% Anemia, weakness, loss of concentration, loss of libido Weight gain on any more than 2100 cals Binge eating after study, all weight regained in 2 weeks And another 8 lbs extra in the next 3 weeks In general- 25% lost 20 lbs, 5% lost 40 lbs Almost all gained it back Keys 1944 32 male conscientious objectors 24 weeks on “semi-starvation” diet- 1570 calories 400 cals protein, 270 fat, 900 carbs Also 5-6 mile walk each day 12 lbs lost in 12 weeks Another 3 the next 12 weeks Slow nail growth, hair loss, increased wound healing time, metabolism down, slowed reflexes, depression, irritability, feeling cold Constant hunger, fixation on food, cheating on diet When allowed to eat, 8000 cals per day Total weight gain 10 lbs Exercise Jean Mayer, 1950’s- inactivity causes obesity But correlation is not causation Two questionable studies, never replicated “J. Mayer has since demonstrated, in both animal and human studies…” -J. Mayer Or… exercise burns calories but stimulates appetite “Consistently high or low energy expenditures result in consistently high or low levels of appetite.” Hugo Rony, 1940 1998: “Energy intake can be interpreted as a crude measure of physical activity.” Exercise Björntorp 1973- 7 subjects, 6 months of exercise three times a week, no change in weight Pi-Sunyer 1989- weights can go up, down, or remain steady Denmark 1989- sedentary people trained to run marathons for 18 months 18 men lost 5 lbs, 9 women lost no weight Randomized trials show less effect Somewhere between 3 ounces a month gained and 2 ounces a month lost Animal experiments- the more the rats run, the more they eat, weights unchanged In hamsters and gerbils, voluntary running produced increases in body weight and body fat Hunger increases in proportion to the calories expended “Working up an appetite” Fattening Diets To fatten- excess calories have to be stored as fat Not stored as muscle, not burned in metabolism or physical activity Continuing excess calorie consumption Massa tribe- Cameroon- fattening ritual Normally- milk as staple, 2500 calories per day To fatten- milk with sorghum porridge, 3500 cals/day Typical gain 15-20 lbs. Fattening by adding carbs Sumo wrestlers Normal Japanese diet 2300 cals/day Upper group- 5500 cals/day, 57% carbs, 16% fat Lower group- fatter, less muscular 5100 cals/day, 80% carbs, 9% fat Overfeeding studies- 10,000 calories of mostly carbs a day, but hunger late in the day Reducing Diets AHA- carb restriction today is a “fad diet” But this was the standard medical treatment for obesity through most of the 20th century- p. 314 The AHA recommended high-carb, low-fat diets for CVD in the 1960’s, then for obesity, and low-carb diets were marginalized Observation- the obese eat more carbs Denmark 1936 21 obese patients, 2 years 1850 calories/day, 25% carbs, 60% fat Cream, butter, olive oil, eggs, cheese, meat 2 lbs weight loss per week, no chronic hunger or fatigue Reducing Diets Donaldson 1920’s: 6 oz meat, 2 oz fat, at each meal, no sugar, flour, alcohol, starch, ½ hour walk 17K patients, 2-3 lbs/wk loss, no hunger Alfred Pennington- DuPont 1949: 20 execs, 9-54 lbs loss, 2 lbs/wk, no hunger, increased physical energy and sense of well-being No calorie restriction- min 2400, avg 3000 Carbs restricted to 80 cal/meal JAMA and Lancet: “Freak Diets!” (p. 331) Thorpe 1957- rapid weight loss (6-8 lbs/mo), no hunger, weakness, lethargy, or constipation Reducing Diets Ohlson and Young 1952: 14-1500 cals/day, 24% protein, 54% fat, 22% carbs 7 women, overweight to obese, 16 weeks, 19-37 lbs lost No hunger, addition of muscle mass 16 overweight women, 9-26 lbs lost in 10 weeks, no hunger, “unexpectedly healthy,” sense of well-being 8 overweight male students, 1800 cals/day, 9 weeks, 1328 lbs lost, almost 3 lbs/week Leith 1961: 48 patients who had tried and failed with low-cal diets, 28 lost btw 10 and 40 lbs “The patients ingested protein and fat as desired” Reducing Diets Wilder 1930’s: a few hundred cals/day, meat, fish, egg white, 80-100 cals of green veggies- weight loss without hunger Bistrian 1970’s: 700 patients, 50% fat, 50% protein, 650-800 cals/day, weight loss without hunger 1000, 1200, 1320, 1400, 1800, 2200, 2700, or no calorie restriction at allweight loss without hunger Kemp 1956: low-carb diet, no calorie restriction 1450 overweight and obese patients 49% lost at least 60% of excess weight- 25# after 1 year 38% defaulted, 13% didn’t lose weight Carb restriction usually does a lot better than low-cal “balanced diet” when compared directly, even when the low-carb diet has more calories- p. 337 6 recent trials- weight loss after 3-6 mos was 2-3x greater on low-carb, calorie-unrestricted diet than on calorie-restricted, low-fat diet JAMA 2003: “Greater weight loss than higher-carbohydrate diets” 37# vs. 4#, p. 339 Reducing Diets “If the Pima Indians could return to some of their traditions, including a high degree of physical activity and a diet with less fat and more starch, we might be able to reduce the rate, and surely the severity, of unhealthy weight in most of the population.” Obesity is a “penalty for living off the fat of the land rather than the carbohydrate” But- start with an 800-calorie fat and protein diet Add 400 more calories of fat and protein for a low-carb weight loss diet Add 400 carb calories, though, and get a “balanced” low-cal semistarvation diet 50X less effective for weight loss Reducing Diets Low-carb diets One fear is that the brain needs glucose 130 grams of carb the “minimum safe levels” But if there’s less than 130 g, the liver makes ketone bodies to supply brain And if no carbs at all, 75% of CNS fuel from ketones The rest from glucose made from amino acids or glycerol Protein from diet or muscle Ketosis- normal- 5-20 mg/dl in 5-10% carb diet Diabetic ketoacidosis- pathological- 200 mg/dl Reducing Diets V. Stefansson- early 20th century Lived with the Inuit for 10 years eating only meat He and the Inuit were vigorously healthy So is the Inuit diet balanced? Conventional wisdom- balanced diet the best Need carbs for brain glucose And to prevent deficiency diseases Deficiency diseases Scurvy- vitamin C Pellagra- niacin (vit B3) Beriberi- thiamine (vit B1) Rickets- vitamin D Anemia- iron, vit B12, folate Fresh fruits and veggies to prevent Reducing Diets All-meat diets considered unhealthy Raise BP, cause gout Monotonous Deficiency diseases Kidney damage 1928- Stefansson and Anderson Ate only meat for an entire year 79% fat, 19% protein, 2% carb (glycogen in muscle) Ketone bodies in urine to rule out carb cheating Both in good condition afterward 6 and 3 lbs weight loss, BP decrease, no kidney damage, no gout, no vitamin or mineral deficiencies, a case of gingivitis cleared up Reducing Diets Deficiency diseases Studies all done with high-carb diets low in meat and dairy- p. 321 Meat contains all essential amino acids And 12 of 13 essential vitamins All in large quantities and in high-utility forms Vitamin C- only small amounts in meat So scurvy can be cured by adding fruits and veggies But this doesn’t mean that the lack of these causes it! Inuit- no fruits, no veggies, no scurvy Could it be that carbs, esp refined carbs, increase our need for vitamins? Reducing Diets Deficiencies B vitamins depleted by carbs in diet Vitamin C also 30% lower levels in type 2 DM Lower vit C in metabolic syndrome too Vitamin C deficiency as a disease of civilization? Mechanism- “biologically plausible and empirically evident” High blood glucose and/or high insulin increase the body’s requirements for vitamin C Vit C similar structure to glucose, transported into the cells by the same insulin-dependent mechanism Glucose and vit C compete, glucose greatly favored So vitamin C uptake inhibited in high blood glucose Glucose also impairs kidney reabsorption of vit C Insulin infusions also cause vit C levels to fall So… carbs flush out the vitamin C and inhibit us from using it So absence of fruits in scurvy, or presence of refined carbs? Energy Balance Change in energy stores = energy intake – expenditure Assumption- intake and expenditure are independent variables We can change one without changing the other USDA- “For most adults a reduction of 50 to 100 calories per day may prevent gradual weight gain.” But- homeostasis- energy regulation involuntary Our bodies minimize long-term fluctuations in energy reserves and maintain a stable weight Unless the set point is changed Energy Balance Set-point hypothesis Energy intake and expenditure are dependent variables Physiologically linked Energy storage determined biologically- p. 299 Interaction of genetics and environment Any increase in energy expenditure induces hunger and increase in intake Any decrease in intake induces decrease in expenditure Slower metabolism or reduced activity Lean people are more active because more of the energy they consume is available as energy, less stored as fatdetermined on a cellular or hormonal level