Wednesday, June 6, 2012

Why We Get Fat 4 : Calories In vs Out

So Part 4 was supposed to be about exercise...but I realized that something had to come first.  And when that something took up as many words as it did...exercise got bumped to Part 5. This is still all good stuff below!

Explaining why we get fat with the "calories in vs calories out" theory goes something like this: we are getting fatter because we overeat and fail to burn off the excess calories. The logic is seemingly straightforward…but is it really an explanation of why we get fat? 

( What do you mean this graphic looks dated?  Shhhhhhhhhh )

Let's say we were talking about why a room is crowded instead of why a person is fat. If you ask me why the room is crowded and I explained it is because more people are entering the room than leaving it…you'd probably think I was being a smart ass. Of course the room is crowded because more people are entering than leaving… but does that really explain why the room is crowded? 

If getting fatter is simply a matter of overeating…then obesity is simply a mental disorder. The obese person makes poor decisions and/or can't control themselves. If a person is aware that overeating is making them fatter and they do it anyway…then they have a behavioral problem.  

This remains the predominant thought process today. Obesity is still largely seen as a behavioral problem/mental disorder. The leading authorities on obesity are psychologists and psychiatrists. Take a moment to consider the strong link between diabetes and obesity…most type 2 diabetics are obese, and many obese people become diabetic. Some refer to the two disorders as "diabesity" as though they're two sides of the same pathological coin. Which they are. How many dead diabetics would there be if they were being treated for a behavioral problem by psychiatrists? We treat diabetes like it is a problem of the body…not the mind…so why don't we treat obesity the same way?

( How'd you get the beetus bro? )

To borrow from Susan Sontag"s essay Illness as Metaphor "Theories that diseases are caused by mental states and can be cured by will power are always an index of how much is not understood about the physical terrain of a disease." So long as we believe that people get fat because they overeat, we're putting the ultimate blame on a mental state, a weakness of character, and we're leaving human biology out of the question. It's a mistake to think this way about any disease. And it's been disastrous when it comes to the question of why we get fat.

( Lay off me I'm starving! Classic. He's dead now! )

This is not to say that people at times don't make poor eating choices. Punishing your intestines at the ol' pizza buffet is something we've all probably done a time or two.  But remember from Parts 1-3 that some doctor's and scientists have been prescribing diets of almost entirely meat and leafy greens to patients for weight loss purposes dating back more than one hundred years. And there is significant recent research/studies that suggest you can eat as much meat as you want and either lose or maintain weight (among other health benefits). So let's not...

Body fat is carefully regulated. Our bodies (when healthy) work diligently to maintain a set amount of fat…the right amount to ensure a steady supply of fuel to cells. Fat tissue isn't a garbage can where excess calories are simply dumped. Consider these examples of when/why/where fat is put on to understand just how regulated of a process it is. (There is an in-depth discussion in Part 1 about how insulin plays a critical role of how fat is regulated in the bloodstream)

1. Men and women fatten differently.  Men mostly store fat above the waist around the belly; women below the waist in the hips, legs, and butt. We also fatten at different times in life mostly related to sex hormones and/or pregnancy.  

( Let's keep this appropriate... )

2. There are parts of our body that are relatively fat free like the backs of our hands or our foreheads which means that local factors play a role of where we fatten. 

3. Entire cultures can be prone to putting on fat in certain areas of the body (like steatopygia in some African tribes). This means that genes from generation to generation influence our fat and where it goes.  

( Steatopygia.  And you thought I made it up... )

4. Some animals are naturally fat, like hippopotami or whales, but they never become obese…meaning they won't suffer adverse health consequences from their fat the way humans do. They won't become diabetic for instance.  

In short fat regulation is a complex process that cannot be reduced down to simply "Oops I ate too much and now I'm obese and unhealthy." 

The book refers to several laboratory studies to walk us through fat regulation. One experiment took common squirrels (who almost double in size in the last months of summer for hibernation during the winter) and carefully regulated their food supply during the "fattening" period.  No matter how little food they were given (short of starving them) the squirrels put on the same amount of weight as they would have in the wild. And even though they didn't have to hibernate during a cold outdoor winter, their bodies still burned all of the excess fat during a warm laboratory winter until they were back to normal size by spring.

( Fat bottomed squirrel you make my rockin' blog go round ) 

The results demonstrate that the amount of fat on these animals at any particular time of year is almost entirely regulated by biological factors and not the food supply or the amount of energy required to gather that food. Which makes sense. Evolution of these animals has led to careful fat regulation so that they will put on and lose the weight at those times regardless of other factors. Otherwise... one bad summer and the whole species would be wiped out.  

When people accumulate excess fat then surely something has gone awry in the careful regulation of their fat tissue. But what has gone wrong and why?

One answer is counterintuitive. What makes us both fatter and heavier is what makes us overeat.  It's not gluttony and sloth that make us fat…rather that getting fatter leads to gluttony and sloth.  

The book references another experiment on rats to demonstrate this point. Scientists removed the rat's ovaries thus depriving them of the sex hormone estrogen. One group of rats were given an unlimited food supply and they ate voraciously and gained significant weight. The second group was given a limited food supply…much less than the first group.  But they gained just as much weight. The first group of rats were fairly active and the second group became sedentary and only moved if it were required to get to their food supply. Their body's recognized that not as much food was available and therefore began expending less energy. A third group of rats was injected with estrogen and continued to eat and maintain weight as if they still had their ovaries. The experiment tells us two things; that there appeared to be an inverse relationship between the amount of food consumed and the level of physical activity of the rats...and that without normal levels of estrogen the rats would gain significant weight.  And also that scientists are weirdos.  Who does that?

( First I'll take your rat's ovaries in my hand...and then shove them down Beakman's throat! )

Consider what happens during growth spurts in humans. Children will consume much more food than they normally do…and will display sloth like behavior. They are taking in more energy than normal but the growth processes are consuming even larger amounts of energy, and therefore the child has little energy to be expended elsewhere. The growth process (spurned by hormones) is the cause of the overeating. We'd never say that the child grew because he overate, or vice versa that a child's growth has been stunted by dieting or too much exercise. Overeating was the direct result of the body growing. The body finds what it needs to grow…whether it's an increase in caloric intake or a decrease in energy expenditure…or both.  

That growth is the cause and overeating the effect is almost certainly true for our fat tissue as well.  We do not grow taller because we eat too much. So why assume that this is a valid explanation for growing fat?  

Consider African elephants and blue whales…the largest land and water animals on the planet. Male elephants can weigh in excess of ten thousand pounds and yet little of their bodies are fat.  Blue whales can weigh three hundred thousand pounds…and much of their bodies are composed of fat.  Elephants will eat several hundred pounds of food per day…and during the summer blue whales will eat thousands of pounds of food per day…but neither species grows so large because they eat so much. They eat so much because they are enormous animals. With or without large quantities of body fat, it's body size that determines how much they eat.  

So what does this say about animals or people who are habitually lean? Over the years, researchers have also created what we might call animal models of leanness--animals whose genes have been manipulated so they are leaner than they'd otherwise be.  These animals will remain lean even when the researchers force them to consume more calories than they prefer. Just as gluttony and sloth are the effects of overeating rather than the cause, eating in moderation and being physically active are the metabolic benefits of a body that's programmed to remain lean. If our fat tissue is regulated so that it will not store significant calories as fat, or our muscle tissue is regulated to take up more than its fair share of calories to use for fuel, then we'll either eat less or be more physically active or both because of it.  Marathon runners aren't lean because they train religiously and burn off thousands of calories doing so, rather they're driven to expend those calories because they're wired to burn off calories and be lean. Just as a greyhound will be more physically active than a basset hound. It's not out of a conscious desire to exercise…but because its body partitions fuel to its lean tissue, not to its fat.  

"It may be easier to believe that we remain lean because of willpower and a commitment to physical activity but the evidence simply says otherwise. Virtue has little more to do with our weight than our height.  When we grow taller, it's hormones and enzymes that are promoting our growth, and we consume more calories than we expend as a result. Growth is the cause -- increased appetite and decreased energy expenditure (gluttony and sloth) are the effects.  When we grow fatter, the same is true as well. We don't get fat because we overeat; we overeat because we're getting fat."

As mentioned before, we all know skinny people who eat all the time and never get fat. You may even know fat people that try hard to lose weight and seemingly can't. Does this mean that nature has dealt us all a hand and that's the end of the story? Most certainly not. But by understanding the information above, maybe we can put less blame on the individual who is fat or's not simply a matter of calories in/out...or that of willpower, control, and character.  

So will exercise keep you skinny?  Probably not!  Read more in Part 5!