2008-02-27
Hunger - drive. Why do you get hungry? Starvation in WW2 prison camps interested scientists. The first study had 36 healthy men. For about 6 months they were given just enough calories to keep their weight normal. Not enough to gain, not enough to lose, and there was normal activity. Then, for six months, they cut their caloric intake in half. Men conserved energy, were listless and apathetic. Body weights dropped 25%. Most importantly they became obsessed with food which was evidence of Maslow's theory. They did not have any motivation to move. They were moody. They didn't care about stuff, but they had mood swings. Their entire society grew around food for those six months. This is where Maslow started with his idea of the hierarchy of needs. Subsequent studies changed the amount of calories, and really it only takes a minor cut in calories before you become obsessed in food. Diets with gradual changes are the ones that tend to work.
Would you swallow a balloon? Wouldn't it be better to just monitor the neurons that send the hunger pangs signals. You can have stomach pangs without stomachs. The hypothalamus controls hunger in the brain and it has two sides. Lateral hypothalamus brings on hunger -- stimulate and will continue to eat, and eat, and eat, and eat until the other portion of the hypothalamus says stop. If you do not have a lateral hypothalamus, you will not eat at all (at least voluntarily). The other side, the ventromedial (stomach-side, middle) hypothalamus (the ventromedial hypothalamus) depresses hunger, gives you stimulation to stop eating. And if you destroy the ventromedial hypothalamus, the intestines will process food faster (obesity) (hypermotility -- food passing through your system without being properly absorbed, so you also have malnutrition. Sugars and fats are absorbed first. Nutrients are absrobed last. And in obesity, this stuff passes through.). They are finding people that are morbidly obese, often have difficulty in that portion of the brain.
Leptin is released by the fat cells in your body. You do not grow fat cells. They only grow larger or smaller. When they are fuller, they send out more leptin, and when they are smaller, they send out less leptin. Leptin's job is to deal with activity level also. It tells you how much weight's on your body, and it tells you how much activity you should be getting. One focuses on the feeding behavior, the other focuses on activity. Could this lead to leptin injections in humans for weight loss? So why not human fat cells in a petri dish and extract the leptin, or do the synthesis? Nobody has done this yet, apparently.
Set point & basal metabolic rate. BMI. Body Mass Index. Set point is a tricky thing, it comes with your genes. You get a card dealt to you that says what your set point is. This is what you, genetically, should have for body weight. It's a range. And you're going to be in that range, given you're healthy, (thyroid, diabetes, tumors, whatever), given that you're healthy, that's your normal range. You can shift to the front or end of the range pretty easily, but beyond your genetic range, you have to work very hard to keep it there, and it bounces back every time you stop doing whatever you do. This is why there's a problem with those people who dip below their set point in dieting ... a set point can, in fact be overweight or an unhealthy point. The more you push below your lower range, the more your body pushes you to the top of your range to keep you safe. Supposedly.
Basal metabolic rate - how much you are expending when you're at rest. When you're a teenager, your body is not ready to settle into its set point, so your body shape right now is not guaranteed. The BMR is a predictor: heart rate, how much you breath, oxygen saturation rate, you can get it measured at the hospital (they take a lot of measurements). Your BMR basically dictates where your set point is going to be. People with lower BMR are not expending as much, are pretty much going to be heavier, because they have a low metabolism.
Appetizer effect - tricks our bodies' normal methods of food regulation. This effect occurs when hunger is stimulated by external stimuli, such as the smell or sight of food or food advertisements. Food advertisements have calculated portions of food that they show in the ad to trigger hunger. This is probably why you walk into a restuarant and you smell food, you say you're hungry or think it, but you're not -- maybe this is more of a neuro-social phenomena that causes you to meet with other people and talk with them about food. This helps the social sharing of food, such as in a hunter-gatherer society, to eat at the same time as everybody else and possibly get new mates etc
Bulimia nervosa - disorder marked with repeated episodes of overeating followed by compensatory vomiting, laxative use, fasting, or excessive exercise. Bulimics binge and purge. This occursi n women in the late teens or twenties. Stomach acid dissolves teeth, errodes your trachea and esophagus, your skin changes, acne, your nails can fall off (toenails too), small intestines stop working, you have rapid motility (diahhrea, constantly), and it's triggered by the chemistry of your body and the chemistry of your brain.
Anorexia nervosa - disorder when a person becomes significantly underweight (15% or more) yet they still feel overweight and are obsessed with losing weight. Develops during adolescence in 9 out of 10 females. The cultural stereotype hurts here ... say you're 115 and you want to be 105. Well, that's nearly your 15% and so it can nearly easily push you into anorexia.