For fat and diabetes we have a general cultural abhorrence today, which is a very recent trend. Mothers exemplify this and children grow up being afraid of fat and diabetes. Removing egg yolks and no ice cream, but instead frozen yogurt. Yet, biologists have come to appreciate that without fat we’d be dead. Without fat, humans wouldn’t be the way we are. Fat is really life.
We associate leanness with health and ofcourse, leanness is a totally different thing. Clearly there are huge sociological players, in how relative degrees of obesity and leanness are perceived. It is obviously not in-built into homosapiens, because there are places in the world where it is perceived different and there are ages and times when it is different. When Rueben was painting the optimal female beauty, it was much larger than the optimal female beauty in 20th century Europe.
Fat isn’t just there to be unpleasant and cosmetically disturbing, it’s there for a function. When we think of mammals, the word that first comes to mind is adaptation. Mammals originally took to foot on planet earth by going into little evolutionary crevices, nitches, caves, cool places, wet places, dark places. We can go quite a long time without food, twice longer than some other animals can. Fat really gave us big advantages in terms of beginning to colonise hostile environments.
Life is about using energy to make more life.
We eat food because it is in the form of energy, in the form of chemical bonds, which we then either burn immediately or we store. There is this constant fluctuation of energy going in and out. When you’re eating a meal, you’re in what is called positive energy, because you are bringing in energy. When you are asleep you are in negative energy mode because you are burning your energy to maintain your body.
Our body resorts to all sorts of tricks to make sure we never run out of energy. The main way we store energy is fat. Fat tissue is quite complex but its primary purpose is to have these resident cells called adipocytes or fat cells and their primary purpose is to be the place where you store this vast amount of lard, a larder for lard.
Fat cells have been described in the past as a fried egg on a beach ball, so the beach ball is the problem of fat and the fired egg is the nucleus with a tiny rim of cytoplasm going all the way around the beach ball. This is the only cell in the body that can occupy themselves with ninety-nine percent of their volume with a single droplet of triglyceride. Triglyceride is a naturally occurring chemical substance and it is the way in which we store fat in chemical terms.
Fat is composed of glycerol with three fatty acid chains coming out of it. Our body is able to beautifully cleave up these fatty acid chains, breaking them of bit by bit as we burn them. A little bit of fat produces vast amounts of energy because fat does burn. If you take a piece of fat that you cut off a lamb chop and you put a match to it and light it, the fat burns.
Whale oil was used as a source of light and heat, which was just melted fat from the whale. There are chunks of fat molecule that are identical to chunks of gasoline molecules. They are just long carbon chains that are full of high energy electrons.
Now, if you simply liberated the fat in your body, by burning it, it would generate a lot of heat that would damage your body. So what the body has learned to do is to extract the energy slowly so that it doesn’t cause destruction. Our body takes off two carbons at a time and we throw those carbons into a Krebs cycle. By running it through a series of chemical reactions, it allows the energy to come out in small bursts in a way that can be captured, but from a physical chemistry point of view it is very similar to burning. You start with a hunk of fat, you end up with carbon dioxide and water and the energy has been released.
The understanding that fat is the place you put excess calories and the understanding of the bio-chemistry of that, has been long standing. It’s like the back store larder. The fat cell is not an intelligent cell and is not doing anything clever, it is just storing away stuff for a rainy day.
In 1994, PPAR(y)2 (PPARgamma2) the master gene of fat was discovered. You can put this DNA binding factor into any cells and two days later you have a fat cell! Hence we learned, how fat forms. The same year saw the publishing of the cloning and identification of leptin, the hormone that lets fat cells talk to the brain.
So leptin comes from your fat tissue, it goes through the blood, it latches onto highly selective and specific receptors in the brain and those turn on a whole pattern of activity within the brain. In one fell swoop, the adipocytes (fat cell) went from being dumb boring cells into being an intelligent member of the neuro-endocrine signalling community.
Your fat is an organ, it is doing stuff. It is talking to muscle, talking to liver, talking to the brain, letting all the other tissues know the status, of energy stores, in the body. Should we signal to slow down the appetite or should we increase appetite.
If you go below a certain amount of storage fat, the drop in leptin suddenly sends a whole lot of clanging alarm signals in the brain. Turn off reproduction, turn off sexual drive, turn on appetitive drive and a whole range of hormonal changes to signal that you are actually going to starve to death.
If women become too thin, whether by anorexia nervosa or by over-training athletically, they stop ovulating. That is a function of adipose tissue. More and more we are discovering that tissues talk to each other and co-ordinate each others’ functions, so it isn’t just the brain or just the fat, or just the muscle. The fat talks to the brain, the brain by eating affects the hormone levels, so the whole thing is really a complex interwoven network that allows the body to do these functions, without things going very much out of control.
Fat is important to all animals but humans aren’t especially adapted to be fat. Even the thin humans who have very little fat on them, by relevant perspective, are extremely fat compared to most primates.
Nothing makes sense except through the prism of evolution.
The average primate was an average 5 – 8% body fat. The average thin human hunter-gatherer is a female who would be 15 – 25% body fat, males likely were 10 – 15% body fat and this was not accidental.
Everybody knows humans have big brains and our brains are four times as large as a chimpanzee’s brain. Brains are very expensive. Even when you are asleep, your brain requires an enormous amount of energy to function.
You spend about 20 – 25% of your resting metabolism to pay for your brain. All the cells are required to constantly re-generate, the neuro-transmitters have the cost of transmitting electrical potentials down each cell and each axon in the brain – the cost of a lot of energy. This means that if you are in a negative energy balance, you are not taking in as much energy as you are expending, then essentially you have to provide that energy from storage which comes from the fat. If you don’t supply your brain with that energy, you are going to die.
If blood sugar drops even once, you would rapidly have a deterioration of cognitive function. You would be equivalent to someone who has just drunk a half a bottle of whiskey. In evolution, even one episode like that and you would be eaten by a sabre tooth tiger!
It takes about three years for a chimpanzee’s brain to grow and another three before the chimpanzee can more or less, feed itself independently. We spend about six years growing our brains and then another twelve years maturing our body.
Mother’s wean infants at a very young age while their brains are still growing. That child is still incredibly unable to take care of itself. That long period of development means we can spend a lot longer adapting that brain to the world around it. Learning languages, learning skills, getting good at complex tasks like cycling. We’ve invented a period of development called childhood unlike any other organism.
From the perspective of the mother, they have to take care of their infants, they have to take care of their nine year olds and this takes energy. A mother can do that by having lots of energy supplied to her on a daily basis but also she needs to have energy reserves. If there ever was a case when energy was limited, mothers who had more fat would have been much more strongly selected, because they wouldn’t have lost their off-spring.
We mustn’t confuse fat with diabetes and other diseases
Fat is essentially generally healthy and an important necessary nutrient. As far as we know there is no evidence for any examples of type 2 diabetes (fat and diabetes) amongst hunter-gatherers. It is extremely rare amongst the subsequent age of farmers and yet it is now one of the most rapidly growing diseases in the world!
We’re in the midst of a worldwide epidemic and not just in the western industrial world. A lot of people don’t realise that type 2 diabetes is out of control in some of the emerging economies like India and China which have terrible epidemics of type 2 diabetes.
The reason it is growing is because we now have access to extraordinary amounts of energy, because today for the first time in millions of years, we’ve created bizarre conditions in which we can be in positive energy balance whenever we want.
Until very recently, humans struggled to stay in energy balance. We never got the chance to become obese because the amount of energy we had to expend in hunter-gathering really never gave you an opportunity to get fat and diabetes type 2 was non-existent.
Once we evolved agriculturally, by inventing agriculture, we began to change. Agriculture, although it is a fair amount of work, can provide many more calories because farmers grow their food. Farmers easily get twice as much energy per day as a hunter-gatherer. That means twice as many off-spring.
So with the emergence of agriculture, we’re also getting an increase in population size which began to grow, grow, grow and grow!
The next enormous transformation is the industrial revolution. We figured out ways to mechanise the production of food and at the same time we’ve substituted work by humans and animals to work by machines.
Automobiles, computers, televisions, automation in manufacturing, few of us are farming, we’ve evolved as animals that move. To hunt, to gather, to migrate and now to be physically inactive, takes us away from our normal healthy state.
Only in the last fifty years, with changes in our food production – refrigeration, packaging – that the average human being can afford enough food to make themselves obese, without having to expend an awful lot of energy.
Today, the average American eats a hundred pounds of sugar a year, whereas our hunter-gatherer ancestors used to struggle to get a pound or two in the whole year! We don’t have metabolisms that are adapted to handling a hundred pounds of sugar a year. If you draw a graph for fat and diabetes, on the y axis you have diabetes presence, on the x axis you have body weight, you will find a very strong relationship. On the average the fat and diabetes relevance are directly proportionate. Fatter you are, the greater the chances that you have diabetes.
You have to dig deeper into biology to understand the nature of that relationship. We think about fat and diabetes being a disease caused by the insulin pathway going awry and we become insulin resistant. In the healthy individual there is incredible tuning, like a musical instrument or like an orchestra, between the levels of glucose and nutrients in the blood and the beta cells secreting insulin. If we have a sweet drink, the blood sugar will go up a bit and they will quickly come back down, but obesity causes insulin resistance. It is where insulin doesn’t work as well as it is supposed to work. Your blood sugar will go up and maybe it’ll go up even higher and it will take a lot longer to come back down to normal.
The mechanisms are not completely understood.
One major thing that happens in obesity is that you have a low level chronic inflammation. The body reacts to obesity at a low level in a similar fashion to the way it reacts to an infection. Infact, obesity could be considered as a low level inflammatory disease and a lot of the components of an inflammatory response interfere with insulin signalling.
It is also true that in obesity, the energy stored becomes greater than the adipose cells can easily handle. So you get what you might think of as spill-over. The safest place to keep fat is your fat cell. The fat cell is your professional fat storing tissue. All the other tissues affected act like amateurs and like a lot of amateurs, they mess things up when they handle stuff they are not designed to handle.
An analogy we can use; it’s really bad for your bathroom, when your bath overflows and let us say that diabetes is the wet carpet that you get. You’re better off having a big bath and the big bath is the size of your safe adipose deposit. You will often see in newspapers, reports of people who are very obese and the fire-brigade comes to knock-off the walls of the house to get them out because they are so vastly obese. These people almost never have diabetes. Their bath is enormous, not linking fat and diabetes. They have almost an indefinite capacity to continue to expand their fat deposits and safely store their excess energy in fat and diabetes type 2 is not a threat.
It is only when we start getting to the limits of our safe fat storage, that we start spilling over the bath. Fat has to go somewhere else, other than the fat cell and it tends to go into the heart muscle, the pancreas, the liver, the blood vessel wall and wreak havoc.
This is known as ectopic deposition. Deposition of energy where it should not occur and that has been shown to also correlate with and in some cases, cause resistance to insulin.
We’re today, asking people to make choices that we never evolved to make. There was never selection for us to lose weight. Our bodies have all kinds of adaptations to prevent us from failing. When you start dieting, you get cranky, cortisone levels go up, food cravings go up, ability and desire to be physically active goes down – this is called a famine response. People will seek out food, if you are starving, you will do almost anything to get food.
No one has any difficulty in understanding they have no real control over their breathing. If you are asked to stop breathing for ten minutes for a million dollars, you’d love to do it but you just simply wouldn’t be able. Control of eating and drinking is not as primal and as brainstem as breathing, but hunger is one of the great drivers of survival.
That doesn’t mean that we don’t have free will, but free will is superimposed on your biological program. It is just as hard for an overweight person to diet, as it is, for a thin person to diet. The same famine response, the same deep adaptations are being enacted. So when we blame people for being overweight, as if it is their lack of willpower, we’re essentially blaming people for being human.
Today we have unlimited access to the foods that we crave and as a result we are getting sick. There is no analogy in the natural world for what we’ve done to ourselves and we remain in uncharted territory.
E316 – Evolution of Fat and Diabetes – www.diabetic.today