One of the biggest self deceptions is wide spread belief that some people eat a ton of calories, don't work out, and are skinny.
The fact is that nobody naturally has a high metabolism that allows you to consume all the calories you want. The best way of understanding this to to look at what it takes to burn a lot of calories, and an an example of this is as close as my other blog.
I have a 62 mile loop that I do on my bicycle. On this loop, there is a lot of climbing, and it is very difficult to do this loop in an easy fashion. On my bicycle, I have special instrumentation (see posts on power meter) that measures direct power and this allows me to get an almost direct measurement of my calorie burn.
This route burns between 2100 to 2300 kilocalories (commonly called just calorie). Yesterday I did this loop in 4.5 hours. During this time my pulse was elevated (120-130 beats per minute). I was constantly sweating profusely from the effort (although I drank 72 ounces, I still lost 6 pounds of body weight or roughly 96 additional oz of body water). Considering the liquid loss from m body, on my skin, appeared over a gallon of sweat. On the bicycle, I rode an average of 13.5 MPH. Without this wind, I would have been drenched with sweat, dripping everywhere I went. (This is just like dumping ove1 quart of water of your body every hour.)
All of this effort, just to burn a little over 2000 calories.
You can replace all of those calories with the following:
1. Two Big Macs
2. 8 Powerbars
3. 2 pints of Haagen Dazs
4. Or a variety of other means
Let me be clear: I mean you can have 1 or 2 or 3 or 4. You can't have all of them. It is well within most people's ability to eat 8 Powerbars in a sitting. It is not, however, within most people's ability to bike my 62 mile loop.
It is really, really hard to burn calories. It is really, really easy to take them in.
See, if you had a metabolism that burned 2000 extra calories per day, you would be in a constant state of being "way too hot." Your heart rate would be constantly elevated, and you'd be twitching all the time because muscle have to move to burn calories.
Now, there are two other ways of not taking on weight, although we don't see them in humans: Non-shivering thermogenesis (which humans really don't do without drugs), which also would make you very, very hot. The other way is if your body simply doesn't digest the food that you eat. If you aren't digesting the food, this is going to be very, very obvious next time that you go to the toliet and examine your stool. If you are like everybody else, what comes out is very, very well digested.
In reality, no matter how much we'd like it to be different, everybody's body works pretty much the same. Now, could there be a variant in the population? The answer is obviously yes, but the range of the variation is going to be more along the 20-30% percentage range. Not the 100-200% range. And this variation may often comes because somebody simply fidgets a lot. Yet, it takes a lot of fidgeting to get skinny.
Below is a chart that shows some of this. This was taken from an issue of the American Journal of Clinical Nutrition. Although the chart is in mJ, you can extrapolate this to be kCalories. For roughly the same weight, certain people can burn 500 calories more than somebody else.
So, is there some variation? The answer is yes. Some people can eat 500 calories more per day than somebody else with the same body mass. This translates into one 36 oz Coke per day. However, this is at the extremes. On average, 80% of the people (at the same lean body mass) are within ~240 kCalories of each other. This is like a couple of glass of skim milk.
So, what does happen with that friend that "eats all she wants?" She really does eat all she wants, but if you measured the food that she eats, you'd find out it is pretty small compared to the people that are increasing in weight.
So why do we put on weight?
In a simple way, it is our brain. In our brain, our hypothalamus controls several fundamental drives. Two critical drives are thirst and appetite.
If your hypothalamus isn't working, you could get dangerously dehydrate, or you could starve to death.
The hypothalamus gets set at a preferred "fat setting." This is commonly called "your set point." What is interesting is that the set point tends to protect us against under eating and overeating. If you are suddenly forced to overeat, you will put on weight. If you are then allowed to stop eating, many people will find out that their appetite goes away until they get to a lower weight.
However, the set point is a bit tricky in that in a majority of people, once you have set a higher fat level, the set point goes up and doesn't come down. The set point also tends to increase as you age.
I'll repeat this for clarity, I have never seen any indication that the set point ever comes down.
So, what happens when you get below your set point?
You feel hungry. All the time. Hungry. This is why the vast majority of people will regain any weight that they lost on a diet. Your hypothalamus is telling you to "eat, eat!"
Now, take some comfort in that if you raise up your fat levels, you can push them down a bit without feeling hungry all the time. Therefore, some people have suggested that while set points are an okay terminology, you might better have "settling points." By eating the appropriate diet, you may be able to settle you body fat lower than you have it now.
What types of food help with controlling appetite?
Generally, we will have a tendency to eat less if we eat more protein and fiber.
What types of food may trigger a relapse? Generally, fatty food.
There is a research project for tracking people who lose weight and keep it off, "The National Weight Control Registry." There are some characteristics of this group.
1. They don't eat a lot of fat.
2. They cut back on their calories on a constant basis
3. They get physical activity
4. They eat breakfast
5. They don't watch television
Now, there are several other things that I believe contribute to keeping weight off due to some of the research and thinking that I've done.
1. Getting more sleep is correlated with lower fat levels
2. Having less stress is correlated with lower fat levels
Finally, the safest drug to temporarily trick the hypothalamus into dropping the setpoint is Bromocriptine, which foul mouthed, but highly intelligent Lyle McDonald has written about in his book "Bromocriptine."
If you are interested in this drug, let me give you the short version:
1. It fools around with your brain since it is a dopamine agonist (it activates dopamine receptors)
2. Although its weight loss properties are not studied extensively, it looks as if it does help with getting below the set point.
3. It is a temporary trick. Once you go off, the effect ends.
4. You need to do some work to get it.
5. It appears to be fairly safe, with a few annoying start up problems.
In my mind (pun intended), the best defense is a high protein, high fiber diet, with physical activity.
However, if all else fails, buy Lyle McDonald's book and decide for yourself on bromo.